Download Proefschrift Veerle Stevens

Ghent University
Faculty of Medicine and Health Sciences
Department of Rehabilitation Sciences and Physiotherapy
STABILIZATION EXERCISES VERSUS RECONDITIONING
ON DEVICES:
TRUNK MUSCLE RECRUITMENT AND EFFECT
ON CHRONIC LOW BACK PAIN
Veerle Stevens
Thesis submitted in fulfilment of the requirements for the
degree of Doctor in Motor Rehabilitation and Physiotherapy
Ghent 2007
Promotor
Prof. Dr. L. Danneels, Ghent University, Belgium
Co-promotor
Prof. Dr. G. Vanderstraeten, Ghent University, Belgium
Examination Board
Prof. Dr. I. Arvidsson, Karolinska Institute, Sweden
Prof. Dr. G. Crombez, Ghent University, Belgium
Prof. Dr. L. Danneels, Ghent University, Belgium
Prof. Dr. I. De Bourdeaudhuij, Ghent University, Belgium
Prof. Dr. R. Gunzburg, Antwerp, Belgium
Dr. T. Parlevliet, Ghent University, Belgium
Prof. Dr. G. Vanderstraeten, Ghent University, Belgium
Prof. Dr. A. Ven, Artevelde University College, Belgium
Prof. Dr. A. Vleeming, Rotterdam, the Netherlands
Process Supervisory Board
Prof. Dr. G. Crombez, Ghent University, Belgium
Dr. T. Parlevliet, Ghent University, Belgium
TABLE OF CONTENTS
General introduction
1
Introduction
3
Outline
11
Part I: Muscle activity during stabilization exercises
Chapter 1:
Electromyographic activity of trunk and hip muscles
21
23
during stabilization exercises in four-point kneeling in
healthy volunteers
Chapter 2:
Trunk muscle activity in healthy subjects during
39
bridging stabilization exercises
Chapter 3:
The influence of specific training on trunk muscle
59
recruitment patterns in healthy subjects during
stabilization exercises
Part II: Muscle activity during exercises on specific training devices
Chapter 4:
The relevance of increasing resistance on trunk
79
81
muscle activity during seated axial rotation
Chapter 5:
The effect of increasing resistance on trunk muscle
activity during extension and flexion exercises on
training devices
97
Part III: Effectiveness of specific exercise therapy versus exercise
125
therapy on devices
Chapter 6:
Reliability of a functional clinical test battery evaluating 127
postural control, proprioception and trunk muscle
activity
Chapter 7:
The effectiveness of specific exercise therapy versus 145
device exercise therapy in the treatment of chronic low
back pain patients
General discussion
175
Summary and clinical implications
177
Future directions
187
General conclusions
188
Nederlandstalige samenvatting
193
ACKNOWLEDGEMENTS
The past 5 years, many individuals have contributed to the doctoral research process that
has led to this dissertation. Without their ideas, assistance, support and encouragement, this
dissertation would not have reached its present form.
First of all, I want to express my sincere gratitude to my promotor, prof. dr. Danneels.
Lieven, several persons warned us for the ambitious plan of our studies and the possible
risks and failures this might involve. And they were right. It was no easy ride. However,
you kept believing in the challenge, the capacities and the success of our project and
encouraged me to get out the best of it. I’ve learned a lot during the past years, not only
about device handling and science, but also about communication with all parties involved.
Thank you for giving me these opportunities and for believing in me. Secondly, I am
indebted to my co-promotor, prof. dr. Vanderstraeten. Thank you for your help in
obtaining the Tergumed devices, for being the essential motivating link between the
Department of Physical Medicine and Orthopaedic Surgery and the REVAKI and for all
encouraging words and animated e-mail cards to congratulate me with publications. I also
wish to express my gratitude to the members of the process supervisory board. Prof. dr.
Crombez, thank you for sharing some of your great expertise in psycho-social assessment
of chronic pain patients. Dr. Parlevliet, thank you for the referral of patients and the
meetings in which the patients were discussed.
I wish to acknowledge the members of the examination board, prof. dr. Arvidsson, prof.
dr. De Bourdeaudhuij, prof. dr. Gunzburg, prof. dr. Ven and prof. dr. Vleeming for their
critical remarks on my dissertation. I would like to express a special word of thank to prof.
dr. Vleeming for the hospitality, the time, the overwhelming enthusiasm, faith and
encouraging words that brightened up cloudy days. I was honoured to receive your great
insights and comments on low back and pelvic pain.
Since the clinical trial was the work of several years evaluating many patients, a lot of
people contributed to the good organization of the protocol. I am grateful to the
Department of Physical Medicine and Orthopaedic Surgery for the referral of patients and
to Juri for the practical arrangements. I warmly thank the Centre of Sports Medicine for
providing the test rooms, Kathleen for solving all practical problems and Fabienne, Saskia,
Hilde, Mike and Benedicte for the interest and help in my research projects.
I thank Dr. Morthier and his staff of the Department of Occupational Medicine of the
Ghent University Hospital for informing all hospital personnel about the research and for
referring the interested patients.
I am also very grateful to the Department of Physiotherapy of the Ghent University
Hospital. Thank you, Sonja and Isabel, for the practical arrangements and thank you,
Nancy and Patrick for your willingness to invest time and knowledge in the treatments on
the Tergumed devices. Filip, thank you very much for the scientific input and your
expertise in the clinical examinations and the specific treatments.
In additon, I would like to thank the REVAKI Gent for the test equipment and EnrafNonius for the technical support.
Warm thanks go to all REVAKI colleagues I was privileged to work and live with those 5
years. The nice talks during breaks, the social events, the help and encouraging words when
needed were the driving force that kept me going. Thank you all! I had a great time at
REVAKI! Special thanks go to Katie, to accompany, help and animate me during a lot of
test sessions and to Pascal for all mathematical and statistical advice and for the humour
from time to time. Youri, thank you to pose for my exercise photographs. Nele, you were
the perfect officemate to me! I am very grateful for our true friendship that developed
during the past years. With a smile, you were always there to discuss and assist with
scientific problems, educational arrangements and personal events. This bond of friendship
will last!
I wish to thank the Belgian Ministry of Defence, especially the Department of
Traumatology and Rehabilitation of the Military Hospital of Base Queen Astrid for the
support and the time to complete my thesis. Thanks to my colleagues for their
encouragements and their interest in my work. Veerle and Damien, also thank you for the
assistance with the cover of this book.
I am grateful to all REVAKI and postgraduate Manual Therapy students for their
assistance in the acquisition and analysis of the data. Also warm thanks to all subjects and
patients who participated in the studies.
Last, but definitely not least, I would like to thank my family and friends for their interest,
their support and the relaxing moments together. My Dirk, I owe most gratitude to you.
You experienced more than anyone else that a PhD is a journey with many ups and downs.
Thank you for being there for me. I hope that the time has come to enjoy our weekends a
bit more, especially since shortly a little boy or girl will change our lives.
Veerle Stevens
Ghent, May 2007
GENERAL INTRODUCTION
General Introduction
INTRODUCTION
Musculoskeletal disorders and complaints comprise an important public health problem
due to high impact on physical functioning1, professional disability2, and health care costs3.
In 2001, low back pain (LBP) for one or more days during the past six months was
reported in 41.8% of a Belgian community sample.4 In the Netherlands, LBP is the most
frequently reported musculoskeletal pain complaint (in a population of 25 to 55-years of
age) and the most important cause of professional disability and resulting sick leave.5 Most
pain complaints are continuous or recurrent.1
In the aim to decrease pain and disability and to curtail the high socio-economic costs
related to chronic LBP (CLBP), several rehabilitation strategies have been proposed.
Recent reviews evaluating the effectiveness of exercise therapy in CLBP showed that
individually designed strengthening or stabilizing programs appear to be effective for
reducing pain and improving function.6-9 However, contradictory findings exist concerning
long-term effects on pain and function.8-9 More intensive programs and rehabilitation that
includes motivational strategies appear to be of greater benefit than less intensive
programs.8 Treatments using exercise alone or as a part of a multidisciplinary treatment
reduce sick leave in non-specific CLBP patients.10 Exercise is also thought to decrease fearavoidance behaviour and facilitate functional improvements, despite ongoing pain.7
Consequently, European guidelines recommend supervised exercise therapy as a first-line
treatment in the management of CLBP, but no recommendations are given on the specific
type of exercise to be undertaken.11 The optimal intensity, frequency and duration of
exercises needs to be further researched. 11
Today, concerning the active approach of CLBP in Western Europe, the
two most
popular rehabilitation strategies are specific exercise therapy and device exercise therapy.
Specific exercise therapy combined with hands-on treatment is based on the findings of the
clinical examination and the daily needs and work complaints of the patient, and intends
functional restoration or improvement.12-13 In this approach, specific stabilization training
often is included. Besides the specific hand-on approach, last years device exercise therapy
became popular due to the low guidance cost since simultaneous individual training of
3
different patients is possible supervised by one physiotherapist. However, expensive
machines are needed.
In the present dissertation, the muscle activity levels during stabilization exercises and
exercises on devices are investigated in order to gain more insight into the working
mechanisms of both therapy interventions. In addition, the effectiveness of both active
approaches is compared.
Muscle activity during stabilization exercises
Joint stability is defined as the effective accommodation of the joints to each specific load
demand through an adequately tailored joint compression (as a function of gravity and
coordinated muscle and ligament forces) to produce effective joint reaction forces under
changing conditions.14 Stabilization exercises are designed to improve function of the
muscles that are believed to govern trunk stability and, when these muscles are functioning
optimally, they will protect the spinal joint structures from further repetitive microtrauma,
recurrent pain and degenerative change.15-16
Different approaches concerning stabilization exercises have been discussed. It remains
unclear whether instruction of stabilization exercises should occur (1) according to the
principles of Richardson et al.13,16,17, focusing on the deep local muscles, or (2) whether
subjects should be asked to perform an abdominal brace manoeuvre (isometric contraction
of all the abdominal muscles)18-20 or (3) whether only the neutral spine position should be
sustained and no muscle instruction should be given21-22.
The first approach focusing on the deep local muscles is based upon in vivo23-24 and in
vitro25 studies, in which the deep local muscles are assumed to provide the ‘fine-tuning’ of
intervertebral motion as a component of the complex interdependent activity of the trunk
muscles to stabilize the spine.13,26 The differentiation between local and global muscles is
anatomically based and has been related to specific functions, respectively segmental
stabilizing (local) and torque producing and providing general trunk stability (global).27
There is evidence that in patients with LBP, the deep local muscle system is often very
dysfunctional.28-40 In addition, consistent differences between local muscle activity of
healthy subjects and LBP patients have been found in contrast to inconsistent findings in
global trunk muscle activity.26
4
General Introduction
A second assumption concerning stability is that an abdominal brace manoeuvre is
beneficial during the performance of stabilization exercises. This idea is based on the
concept that muscles act as guy wires to ensure sufficient stability by creating a spring-like
stiffness around the joints that they cross.20,41 A muscle’s line of pull is considered to play a
large role in determining the ability of the muscle to stabilize, as does the balanced stiffness
and stiffness symmetry around the spine.41 In this respect, no single muscle can be
identified as being the most or least important in stabilizing the spine.18,19,42 However, coactivation of the superficial muscles, as proposed during an abdominal brace manoeuvre, is
assumed to create a loading cost.43 Moreover, increased stiffness is not the only
contributing factor to optimal stability; movement of the spine is required to dissipate
forces and minimize energy expenditure.44 In healthy subjects it was shown that the central
nervous system uses movement rather than simple stiffening of the spine to overcome
challenges to stability.45
The third concept concerns the neutral spine position. Most exercises are performed in a
neutral spine position. Some researchers and clinicians suppose that maintaining a neutral
spine position during stabilization exercises is the only instruction needed to ensure
optimal performance.21-22 The neutral spine has been advocated as a safe position for
exercises46 due to optimal spine loading47. In this position the joints and surrounding
passive tissues are in elastic equilibrium and thus at an angle of minimal joint load.47 Full
flexion causes the interspinous ligament complex to strain, imposing an anterior shear
force on the superior vertebra. Avoiding full flexion not only ensures a lower shear load
but also eliminates ligament damage.20 A fully flexed spine is significantly compromised in
its ability to withstand compressive load.20 In an extended lumbar spine position, such as
during the exercise in which the patient lies prone and extends the legs and outstretched
arms, the imposed load on the spine was demonstrated to be up to 6000 N. Consequently,
the researchers concluded that this kind of extension exercises are not justifiable for any
patient.20,48 The neutral spine position is assumed to create optimal orientation of all
surrounding trunk muscles by which adequate contraction is enhanced during exercises. In
this respect, demanding extra preparatory contraction of certain muscles seems redundant.
In conclusion, most recent research demonstrated that all trunk muscles are required for
control and stability of the spine15,18,19,49 and indicated that stability is dependent on the
interplay between an array of muscles, both local and global15,42. The individual muscular
5
contribution to spine stability seems to depend greatly on the demands (i.e., loading
magnitude and direction) of the task.15,18
Differences in activation29,38, fatiguability28,37, timing32-35, composition39-40 and crosssectional area30,31,36 of trunk muscles have been demonstrated between LBP patients and
healthy controls. In order to comprehend the reason for changes in muscle activation
related to LBP, knowledge about the muscle characteristics in healthy individuals is needed.
Amplitudes of muscle activity in healthy subjects were analyzed during various stabilization
exercises.21,50-60 However, often, the reported results were incomplete. Concerning the
abdominal muscle activity, several studies investigated only the activity of the rectus
abdominis (RA) and external oblique (EO)21,51,54,55,58,59,60, both classified as so-called global
muscles. Concerning the back muscle activity, the erector spinae muscles were often
considered as one muscle group.52,56-59 Consequently, a complete overview of relative
abdominal and back muscle activity is scarce. Since the interplay between local and global
muscle systems is considered important, analysis is needed to detect the relative
contribution of the local to global relative muscle activity, presented as ratios.
Muscle activity during exercises on specific training devices
During the last years, a few companies have developed devices aimed at creating optimal
isolated training of the muscles of the lumbar spine region.
In general, two kinds of training equipment can be observed. The first group of devices
comprises specific machines aimed at training strength of the abdominal and back muscles
by asking the patients to move with maximal force through a predetermined range of
motion (ROM). During this type of exercises frequently no specific performance
instruction is given and the execution is usually not controlled.61
The second group of devices aims to create controlled movements in which constant
biofeedback on a computer display serves as an automated “coach”, cuing the patient for
cadence and effort.29 In this way, not only strength, but also muscle coordination is
expected to be trained.
In both types of devices, debate exists on the need for pelvic stabilization. Pelvic
stabilization was shown to be necessary for restricting pelvic motion62, for isolating and
6
General Introduction
strengthening the lumbar erector spinae muscles63 and to obtain higher activity of the
lumbar multifidus (MF)64 during extension movements on devices. In contrast, other
researchers reported that pelvic stabilization did not influence muscle forces62,65,66 and
activation of gluteus maximus (GM) and hamstrings67.
Evaluation of muscle activity during dynamic low back training exercises on specifically
designed devices is scarce.64,67 Today, in most rehabilitation centres, this strategy to train the
lower back is popular. The advantage is that several patients can train simultaneously while
only accurate instruction and supervision is needed. Although this kind of rehabilitation is
very popular, little research was done to improve the insight in the muscle functioning
during these exercises. A combination of isometric and dynamic exercises is common in
rehabilitation programs. However, most studies analyzing flexion, extension and rotation
movements investigated only isometric exertions.68-92 Analysis of dynamic exercises is
needed since more complex loading on the spine is created in comparison with static
exercises93 and controlled motions are more related to daily life conditions94. Despite the
common use of training devices in clinical practice, most research findings are based on
varied positions and complicated settings. Today, the effect of various loads applied to
dynamic flexion, extension and rotation movements was not yet reported.
Effectiveness of specific exercise therapy in CLBP
Most of the clinical trials describing the effectiveness of specific exercise therapy including
stabilization exercises are based on the principles differentiating and integrating the local
and global muscle system as described by Richardson et al.13,16,17
Ten to 12 sessions of specific stabilization exercises spread over 4 to 10 weeks to
rehabilitate specific (spondylolysis-spondylolisthesis) and nonspecific CLBP was shown to
reduce significantly pain intensity95 and functional disability95,96, even through 30-month
follow-up95. Evidence was also provided that the abdominal muscle activation patterns can
be altered by these specific exercise interventions.97
A combination of manual therapy and specific stabilization exercises98, sometimes
combined with education99,100 for a period of 4 to 12 weeks (4 to 19 treatment sessions) was
reported to improve pain intensity, functional disability98-100, ROM99 and the physical
7
component of quality of life98,100. However, at 12-month follow-up, no consensus was
found regarding the effectiveness of this specific exercise therapy in comparison with more
general exercise therapy or physician consultation.98,100 At 2-year follow-up, except for
patient satisfaction, no indications were present to recommend this specific exercise
therapy over educational information by a physician.101
When comparing the long-term effects of combined specific stabilization exercises and
basic ergonomics to combined manual therapy and basic ergonomics during 6 to 10 weekly
sessions, specific stabilization training appeared to be more effective in reducing the need
for recurrent treatment periods.102 Manual therapy was appropriate as a pain reducing
modality in CLBP, but was not advised as an isolated modality because it did not
concomitantly reduce disability or improve quality of life.103
Sixteen sessions of specific stabilization exercises combined with abdominal and back
muscle strength training at 60-70% of their maximum activation level appeared to be no
more beneficial than trunk strength training as a single therapy.104-105 A combination of
dynamic back muscle training at similar intensity levels with specific stabilization exercises
over 30 therapy sessions showed similar results.106-107 However, a combination of specific
stabilization exercises with dynamic back muscle training including a 5-second static phase
was able to create hypertrophy of the MF muscle.107
Two studies evaluated the effectiveness of a specific exercise program in which
maintenance of a neutral spine position was the only instruction during the performance of
stabilization exercises. Three months of active rehabilitation with ergonomic advice, which
included 4 to 6 outpatient visits and additional self-motivated unsupervised home training,
failed to decrease the pain intensity and the functional disability in a small CLBP
population.21 In contrast, after 12 months (1 guided and 1 unguided session per week) of
motor control training and counselling with cognitive-behavioural learning goals, the pain
intensity was significantly more decreased compared to the results of a control group.22
Aure et al.108 evaluated the effectiveness of 16 treatment sessions (2 sessions per week) of
strengthening, stretching, mobilization, coordination and stabilization exercises for the
trunk and lower limbs, combined with daily home exercises, brief anatomic and ergonomic
information and encouragement for recreational sport at least 3 times per week. No
specific instructions concerning muscle activation were given during the coordination and
stabilization exercises. Significant improvements in pain, general health, functional
8
General Introduction
disability and spinal ROM were observed immediately after the intervention period and this
improvement was maintained throughout the 1-year follow-up. However, in comparison to
the same amount of manual therapy sessions, the exercise group showed significantly
smaller improvement. Moreover, at all follow-up moments, significantly more patients in
the exercise group were sick-listed when compared to the manual therapy group.108
In conclusion, although contrasting findings are present concerning both stabilization
training with and without specific muscle contraction instruction, this kind of exercise
therapy is capable of improving pain intensity and functional disability, and maintaining the
improvement throughout 1-year follow-up.
In all but one of the studies the patient population was a heterogeneous group. Only
O’Sullivan et al.95,97 included systematically patients with spondylolysis or spondylolisthesis.
The cost B13 research group recommended to determine the effectiveness of specific
interventions aimed at specific clinical sub-groups of CLBP patients. Although several
classification systems have been proposed109-114, well-defined criteria and reliable assessment
tools are often lacking. In the present dissertation, we decided to select a well described
sub-group of CLBP patients with motor control impairment.115-116 The classification system
to determine motor control impairment was recently shown to be highly reliable by
experienced clinicians.117
Effectiveness of exercise programs on specifically designed devices
Exercises on MedX training devices during 14 to 16 treatment sessions over 8 to 10 weeks
were shown to improve pain intensity, physical impairment, trunk extension strength118-119,
and general health118. The MedX lumbar extension device of the MedX Corporation
(Ocala, US) with a pelvic stabilization system trains the lumbar extensors in a seated
position. Eighteen 1-hour sessions over 9 weeks on MedX equipment combined with
aerobic exercises, strength training of abdominals, hamstrings and glutei muscles,
educational videos, body mechanics education and specific literature showed to improve
significantly static and dynamic extensor strength and sagittal ROM in a diverse CLBP
population.120 Twenty-four treatment sessions over 12 weeks on David Back Clinic (DBC)
(DBC International, Vantaa, Finland) machines combined with stretching and
9
relaxation61,121-123, functional muscle and coordination exercises, behavioural support and
ergonomic
advice124-126
was
reported
to
improve
pain
intensity,
physical
impairment61,121,124,125 and spinal ROM61,125, and increase lumbar muscle endurance123-124 and
trunk flexion123,125 and extension123,125 strength. Fear-avoidance beliefs and catastrophizing
were also reported to decrease after rehabilitation on devices.61,121 The DBC equipment
with a hip lock system to stabilize the pelvis comprises four different lumbar devices in
which seated training in different directions is performed.
In general, positive effects were maintained over the subsequent 12 months.120,122,124,125
However, some patients were strongly encouraged to follow a continuing individual
exercise program after the intervention120,125 which may have influenced the long-term
outcome. Improvements in lumbar endurance were maintained until 6 months follow-up123124
, but tended to diminish at 1-year follow-up124. Mannion et al.61,121-123 compared device
therapy with physiotherapy and aerobics. In general, no significant differences were found
between the three treatment interventions. The flexion, rotation and lateral flexion strength
improved more in the device group, but the estimated improvement in fitness was
significantly smaller in the device group in comparison with both other interventions. The
lumbar ROM increased significantly more in the device exercise and the aerobics group
than in the physiotherapy group.61
In a male Dutch military and civilian nonspecific CLBP population following 10 training
sessions on a modified lower back test and training machine (Technogym, Italy), spread
over 12 weeks, high-intensity (load > 35% of maximal isometric strength) and low-intensity
(load ≤ 20% of maximal isometric strength) training created similar improvement in
functional disability and general health.127 The high-intensity training group showed a
higher strength gain, but a smaller decline in kinesiophobia compared to the low-intensity
training group.127
The rather similar 8 to 12 weeks intervention periods utilizing specifically designed devices
appear to be capable of positively affecting pain, functional disability, cognitive behaviour
and strength. The device rehabilitation adapted in these studies aimed at gradual training of
trunk muscle strength. In clinical practice, no standard agreement concerning the velocity
of exercise performance on these devices is present. Consequently, the velocity may have
differed in the various studies. In contrast, the training devices used in the present
dissertation (Tergumed), prescribe controlled ROM and velocity, displayed on a computer
10
General Introduction
screen in front of the patient in order to train not only trunk muscle strength, but also
trunk muscle coordination. More controlled training is supposed to be clinically valuable;
consequently, the training effects may differ. However, this was not yet investigated.
OUTLINE
The main purpose of rehabilitation programs is to relieve pain and/or improve physical
functioning. In that respect, exercise programs have been shown to be effective in CLBP.
However, to gain insight into the working mechanisms of this kind of rehabilitation
programs, the exercises themselves need to be examined.
In the past, much attention was paid to strength, endurance and muscle timing.33,34,128-136
However, the amount of muscle activity and the way the different trunk muscles work
together needs to be further elucidated.
Consequently, in the first part of this dissertation, the muscle activity during often used
stabilization exercises is investigated in healthy subjects. Although some stabilization
exercises were recently analysed, a clear overview of relative muscle activity levels was
lacking concerning bridging exercises and exercises in four-point kneeling.
In chapter 1, the relative activity levels (low, moderate, high) of various abdominal, back and
hip muscles are investigated during exercises in four-point kneeling in a healthy population.
In chapter 2, not only the relative activity levels, but also ratios of relative activity provide
more insight in the trunk muscle recruitment patterns during bridging exercises in healthy
subjects. In those 2 studies, no specific muscle contraction instruction is imposed. These
studies intend to gain a better insight in the recruitment patterns in a normal, non
instructed way.
Since during the last years much evidence was compiled to promote cocontraction of the
local trunk muscles to prevent the onset or recurrence of LBP symptoms, in chapter 3 the
ability to change trunk muscle recruitment patterns in a healthy population using a short
intervention period is investigated.
As the costs for health insurances, employers and not at least for the patients themselves
concerning loss of quality of life, seem to increase to huge proportions, a call for effective
prevention strategies is evident. Secondary prevention programs including specific motor
11
control training were shown to prevent recurrent pain episodes in LBP patients.95,102,137
Primary prevention strategies are often evaluated by prospective studies based on the
number of injuries over a certain period. As muscle activation programs are often used in
prevention strategies, it is necessary to evaluate the possibility of changing muscle
activation patterns in a pain free population. Structured training programs that emphasize
motor control and increase functional stability offer encouraging evidence for the
prevention of knee injuries in sports.138-140 It was suggested that the decrease in injury
incidence in trained female athletes might be due to increased dynamic stability of the knee
joint after training.141-144 Concerning the lower back, as buckling of the spine at a single level
was already witnessed in vivo as a potent spine injury mechanism20, specific stabilization
exercises seem useful in the prevention of low back injuries.
In the second part of this dissertation, greater insight into the working mechanisms of
exercises on specifically designed devices is aimed. Similar to the studies concerning the
stabilization exercises, the relative trunk muscle activity is analysed; since different loads are
applied on those machines the effects of increasing resistance levels are investigated. In
chapter 4, analysis of seated axial rotation movements occurs and in chapter 5, flexion and
extension exercises are evaluated.
Finally, having obtained greater insight in the muscle recruitment patterns, the third part
of this dissertation focuses on the effectiveness of specific exercise therapy versus muscle
reconditioning on devices.
Extensive outcome measures are considered to determine the treatment effects. On one
hand, reliable and validated questionnaires describing pain, functional disability, health and
psycho-social characteristics are used.145-150 On the other hand functional tests are applied.
Recently an extensive review was published of reliable measures of low back function, but
only strength, endurance and ROM measures were presented.151 Although it was shown
that these characteristics are often impaired in LBP patients152--161, reliable evaluation of
other variables is needed. Clinical experience demonstrates that muscles are not only
important during force exertions, but that an optimal activation is also needed during lowloaded tasks and postures. A functional clinical test battery developed to measure the
quality of components of functional stability (muscle functional characteristics,
neuromuscular control and postural control)162 is used.
12
General Introduction
In order to obtain reproducible and repeatable functional measurements, a reliability
analysis is conducted (chapter 6).
Chapter 7 presents a randomized clinical trial in a CLBP population with a motor control
impairment.
I: MUSCLE ACTIVITY DURING STABILIZATION EXERCISES
-
Electromyographic activity of trunk and hip muscles during stabilization
exercises in four-point kneeling in healthy volunteers
-
Trunk muscle activity in healthy subjects during bridging stabilization exercises
-
The influence of specific training on trunk muscle recruitment patterns in
healthy subjects during stabilization exercises
II: MUSCLE ACTIVITY DURING EXERCISES ON SPECIFIC TRAINING
DEVICES
-
The relevance of increasing resistance on trunk muscle activity during seated
axial rotation
-
The effect of increasing resistance on trunk muscle activity during extension
and flexion exercises on training devices
III: EFFECTIVENESS OF SPECIFIC EXERCISE THERAPY VERSUS
EXERCISE THERAPY ON DEVICES
-
Reliability of a functional clinical test battery evaluating postural control,
proprioception and trunk muscle activity
-
The effectiveness of specific exercise therapy versus device exercise therapy in
the treatment of chronic low back pain patients
13
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20
PART I: MUSCLE ACTIVITY DURING
STABILIZATION EXERCISES
21
22
CHAPTER 1
ELECTROMYOGRAPHIC ACTIVITY OF TRUNK AND HIP
MUSCLES DURING STABILIZATION EXERCISES IN FOURPOINT KNEELING IN HEALTHY VOLUNTEERS
Veerle K. Stevens1, Andry Vleeming2, Katie G. Bouche1, Nele N. Mahieu1,
Guy G. Vanderstraeten1, Lieven A. Danneels1
1
Department of Rehabilitation Sciences and Physiotherapy; Faculty of Medicine and
Health Sciences, Ghent University, Ghent, Belgium
2
Spine and Joint Centre, Westerlaan 10, 3016 CK Rotterdam, The Netherlands
European Spine Journal 2007;16(5):711-718
23
Chapter 1
ABSTRACT
Stabilization exercises are intended to optimize function of the muscles that are believed to
govern trunk stability. Debate exists whether certain muscles are more important than
others in optimally performing these exercises. Thirthy healthy volunteers were asked to
perform three frequently prescribed stabilization exercises in four-point kneeling. The
electromyographic activity of different trunk and hip muscles was evaluated. Average
amplitudes obtained during the exercises were normalized to the amplitude in maximal
voluntary isometric contraction (% MVIC). During all three exercises, the highest relative
muscle activity levels (>20% MVIC) were consistently found in the ipsilateral lumbar
multifidus and gluteus maximus. During both the single leg extension (exercise 1) and the
leg and arm extension exercise (exercise 2) the contralateral internal oblique and ipsilateral
external oblique reached high levels (>20% MVIC). During exercise 2 there were also high
relative activity levels of the ipsilateral lumbar part and the contralateral thoracic part of the
iliocostalis lumborum and the contralateral lumbar multifidus. During the leg and arm
extension exercise with contralateral hip flexion (exercise 3) there were high relative muscle
activity levels of all back muscles, except for the latissimus dorsi muscle. The lowest
relative muscle activity levels (<10% MVIC) were found in the rectus abdominis and the
ipsilateral internal oblique during all exercises, and in the contralateral gluteus maximus
during exercises 1 and 2. The results of this study show that in exercises in four-point
kneeling performed by healthy subjects, hip and trunk muscles seem to work together in a
harmonious way. This shows that when relative activity of muscles is measured, both
“global and local” muscles function together in order to stabilize the spine.
KEY WORDS
Stabilization exercise – Trunk and hip muscles – Electromyography
24
Trunk and hip muscle activity during stabilization exercises in four-point kneeling
INTRODUCTION
Joint stability is defined as the effective accommodation of the joints to each specific load
demand through an adequately tailored joint compression (as a function of gravity and
coordinated muscle and ligament forces) to produce effective joint reaction forces under
changing conditions [43].
To meet this requirement for joint stability, specific training of the local muscles, like the
lumbar multifidus (MF) and transversus abdominis (TA) muscles has been advocated [17,
35-38]. In particular, the difference in timing in so-called local and global muscles during
specific exercises has been extensively investigated [18, 20, 21, 23]. In contrast, the current
study focuses mainly on the evaluation of normal co-operative activity of several muscles
by measuring the relative activity of these muscles.
The division into a local and global muscle system refers to the functional classification to
discriminate between the muscles responsible for inter-segmental stability (local) and spine
motion (global), based on the anatomical division proposed in 1989 by Bergmark [7]. More
current research based on relative muscle activity levels and stability analysis has shown
that because this classification is not necessarily correct, some rethinking may be required
[10, 26, 27, 32].
The division of trunk muscles into local and global ones mainly results from seeing the
muscles in isolation and not taking into account their intricate functional relationship with
collagenous structures like the fascia. An example could be the action of the gluteus
maximus (GM) and latissimus dorsi (LD); within the framework of local and global, these
muscles would typically be classified as global [7]. However, Vleeming et al [44] have
proposed that tension in the posterior layer of the thoracolumbar fascia (TLF) induced by
the latter muscles may contribute to limitation of joint movement by simultaneously
stiffening the muscles and fascia of the lumbar spine and sacroiliac joint while enabling
transfer of loads between trunk and limbs. Besides the LD and GM the posterior layer of
the TLF also has connections to the abdominal internal and external obliques, which was
confirmed by Barker et al [4].
Stabilization exercises are designed to improve function of the muscles that are believed to
govern trunk stability and, when these muscles are functioning optimally, they will protect
the spine from trauma [10]. Stabilization exercises are often used in clinical practice. The
25
Chapter 1
four-point kneeling position provides a relatively low-loaded, non-anti-gravity posture in
which good balance can be easily achieved when a neutral spine position is maintained [14,
31].
The single leg extension task in four-point kneeling provides both low joint loading and
limited muscular activity, suggesting that this position could be an appropriate choice for
persons starting a rehabilitation program for lumbopelvic pain [8]. In four-point kneeling
an isolated contraction of the inferior fibres of the internal oblique muscle (IO) can be
achieved more often and more consistently compared with a prone position [6, 38]. Haynes
[15] suggests that the four-point kneeling exercise involves the whole body and in this way
it could prepare the muscular loop and slings for upright bipedal functional tasks.
Although these kinds of stabilization exercises are often used in clinical practice, a clear
description of the relative muscle activity during these exercises has only been described in
small unisex populations [27, 31], or with a restricted focus on certain muscles [1, 40].
Therefore this study investigated the relative activation level of certain trunk and hip
muscles during these exercises in four-point kneeling. In this way a normative database,
which is necessary to interpret the results of patients performing these exercises, can be
created.
MATERIALS AND METHODS
Study Participants
Thirty healthy volunteers (15 men and 15 women) participated in this study; their mean age
was 19.6 (range 19-23) year, mean height was 176.6 (range 157-194) cm, and mean weight
was 66.9 (range 42-84) kg. All subjects signed an informed consent. The subjects had no
previous experience with stabilization exercises. Subjects were excluded if they reported
any past or current low back pain (LBP), current neurologic deficits, and/or pain or
disability of the upper or lower limbs. The Ethics Committee of the Ghent University
Hospital approved the protocol.
26
Trunk and hip muscle activity during stabilization exercises in four-point kneeling
Equipment
The skin was prepared by shaving excess hair and rubbing the skin with alcohol to reduce
impedance (typically ≤ 10 kOhm). Disposable Ag/AgCl surface electrodes (Blue Sensor,
Medicotest GmbH, Germany) were attached parallel to the muscle fibre orientation,
bilaterally over the following abdominal muscles: internal oblique (IO) [13, 24, 41], external
oblique (EO) [8, 9, 13, 24, 41, 42] and rectus abdominis (RA) [2, 3, 8, 9, 13, 40]. Marshall et
al [30] showed that on the site medial and inferior to the anterior superior iliac spine, the
fibers of the TA and IO are blended, so a distinction between the muscle signals cannot be
made in this location. The selected back muscles were: lumbar multifidus (MF) [11, 29], the
lumbar part of the iliocostalis lumborum (ICLL) (lateral to the vertical line through the
posterior superior iliac spine, above the iliac crest) [29] and the thoracic part of the
iliocostalis lumborum (ICLT) [11, 13, 29]. Regarding the arm and leg movements, the
activity of the latissimus dorsi (LD) [13] and gluteus maximus (GM) [13] were measured.
The maximum interelectrode spacing between the recording electrodes was 2.5 cm as
recommended by Ng et al [33], and each electrode had an approximately 1.0 cm² pick-up
area. The raw surface electromyographic signals were analogue/digital (A/D) converted
(12-bit resolution) at 1,000 Hz (MyoSystem 1400 Noraxon).
Three-dimensional data of the movements were collected by using an ultrasonic movement
analysis system (Zebris CMS 50, Isny, Germany) with local markers. Spatial marker
positions were derived by angulation and used to standardize the angular positions of the
lumbar spine (L1, L3 and L5) in the sagittal plane.
Data acquisition
Maximum voluntary isometric contractions (MVIC) of the muscles were measured in three
trials before the experimental tasks. These exercises were performed to provide a basis for
EMG signal amplitude normalization [1-3, 6, 13, 24, 40, 42]. Danneels et al. reported a
description of the different isometric exercises [13].
After the registration of the MVICs, the subjects performed three experimental exercises
often used in clinical practice to train stability of the lower back. These exercises were
performed in the four-point kneeling position with movements of the extremities of both
sides (Figs. 1, 2, 3). The exercises were executed in a random sequence. To standardize the
position of the subject and the equipment, markers were placed on the floor. At the
beginning of each exercise a neutral spine position was assumed by the examiner and the
27
Chapter 1
subject was encouraged to hold this position during the course of the total exercise. The
neutral spine position was set about halfway between full extension and a flat position of
the spine [11]. The dynamic phases, lifting and lowering of the extremities and movement
of the trunk, lasted 2 s. During the static phase, the leg was held for 5 s in an extended
position. The pace of 60 beats/min was set by a metronome. Three trials for every exercise
were performed. A pause of at least 15 s was allowed between the trials. The starting
positions of the lumbar spine were determined in the sagittal plane. The complementary
angle between the line connecting the markers on the spinous process of L1 and L3 and
the line connecting the markers on the spinous process of L3 and L5 was calculated.
Fig. 1 Exercise 1: Single-leg lift, performed by extending the leg out to the horizontal and returning it to the
basic four-point kneeling position
Fig. 2 Exercise 2: The leg extension of exercise 1 coupled with the simultaneous raising of the contralateral
arm to the horizontal and then returning to the basic four-point kneeling position
Fig. 3 Exercise 3: The same as exercise 2, but coupled with 30 degrees increased hip flexion
28
Trunk and hip muscle activity during stabilization exercises in four-point kneeling
Data analysis
For the EMG amplitude analysis, manually selected, artefact-free, raw EMG sections were
used. The stored data were full-wave rectified and smoothed. For each of the muscles the
root mean square (RMS) was calculated for the three repetitions of the different exercises.
The mean MVICs were used to provide a basis for EMG signal amplitude normalization.
The static phases of the exercises were analysed, using an interval of 4,700 ms after the
defined starting point of the holding position. The mean (of the three repetitions)
normalized EMG values were calculated. Noraxon MyoResearch software 2.10 was used.
The ipsilateral and contralateral muscle activity values during the asymmetric bridging
exercises were averaged. Ipsilateral involved the same side as the extended leg and
contralateral represented the other side. Three general activity levels were created: high,
moderate, and low relative muscle activity.
Statistical analysis
Statistical analyses were performed using SPSS 11.0 software package (SPSS Inc., Chicago,
IL) for Windows. The level for statistical significance was set at α = 0.05. A two-way
analysis of variance (ANOVA) was used to analyse the effects of the factors muscle and
exercise. There was a significant interaction between the two factors (P < 0.001).
Consequently, least significant difference LSD post- hoc tests were performed on the
differences between the muscles in the separate exercises. Given the huge amount of data,
only the most relevant differences in relation to the research question are presented in the
results section.
RESULTS
Figures 4 and 5 present the relative EMG levels (% MVIC) of the different muscles, and a
classification is made into high, moderate and low muscle activity.
The muscles that show high relative activity (>20% MVIC) during all exercises are the
ipsilateral MF and GM; the difference in activity between these two muscles is not
significant (P ≤ 0.44). During exercises 1 and 2 the abdominal obliques, contralateral IO
and ipsilateral EO, show a similar high relative muscle activity (P ≤ 0.86). During exercise
3, both the ICLL and ICLT (on both sides) have high activity levels. In contrast, during
29
Chapter 1
exercise 2, only the relative muscle activity of the ipsilateral ICLL and contralateral ICLT is
high. During exercises 2 and 3, the relative muscle activity of the contralateral MF is high.
The muscles that demonstrate a moderate relative muscle activity (10 to 20% MVIC) during
all exercises are the contralateral EO and the bilateral LD; there is no significant difference
between the activity of the contralateral EO and the LD (P ≤ 0.94), or between the two
LD muscles (P ≤ 0.74). The abdominal obliques, contralateral IO and ipsilateral EO (no
significant difference: P = 0.41), and the contralateral GM show a moderate relative muscle
activity only during exercise 3. The relative muscle activity of the GM is not significantly
different from the activity of the abdominal obliques during this exercise (P ≤ 0.22). The
contralateral ICLL and the ipsilateral ICLT show similar (P ≤ 0.76) moderate activity levels
during exercises 1 and 2. In addition, the ipsilateral ICLL and the contralateral ICLT and
MF show moderate activity levels only in exercise 1; in this exercise the difference between
the ICLL and ICLT muscle activity is not significant (P = 0.93), but the relative muscle
activity of the contralateral MF is significantly lower than that of the ipsilateral ICLL (P =
0.01) and the contralateral ICLT (P = 0.01).
A low relative muscle activity (<10% MVIC) is created by the ipsilateral IO, the
contralateral GM (except for exercise 3), and the bilateral RA. The bilateral RA shows a
significantly lower relative muscle activity compared with all other muscles during all
exercises. In exercises 1 and 2 the ipsilateral RA is also significantly lower than the
contralateral RA. In exercise 1, the contralateral GM muscle activity is significantly lower
than the ipsilateral muscle activity of the IO, but not in exercise 2.
The measurements of the lumbar curve in the sagittal plane at the beginning of the
exercises were 13.06° ± 5.00° (range 4.17° - 21.87°) in exercise 1, 12.65° ± 4.77° (range
3.08° – 21.19°) in exercise 2, and 11.72° ± 3.95° (range 3.47° - 19.58°) in exercise 3.
30
Trunk and hip muscle activity during stabilization exercises in four-point kneeling
Fig. 4 Abdominal and hip muscles: relative EMG activity and 1 SD. I ipsilateral; C contralateral; IO internal
oblique; RA rectus abdominis; EO external oblique; GM gluteus maximus
Fig. 5 Back muscles: relative EMG activity and 1 SD. I ipsilateral; C contralateral; MF lumbar multifidus;
ICLL iliocostalis lumborum pars lumborum; ICLT iliocostlis lumborum pars thoracis; LD latissimus dorsi
31
Chapter 1
DISCUSSION
The present study investigated the relative activation levels of major trunk and hip muscles
during exercises in four-point kneeling. A classification into three general activity levels was
created, and a possible relationship with the anatomical classification of local and global
muscles was studied.
The ipsilateral GM and MF show a high relative muscle activity (>20% MVIC) during all
exercises in four-point kneeling. Although this is in accordance with earlier studies [1, 8,
40], the latter results are only available for certain muscles, and only for exercises 1 and 2.
In addition, our results seem to indicate that the chosen sequence of the presented
exercises challenging the balance and whole body stability, correlates with increased and
more varied muscle activity.
The results also show a high activity of the contralateral IO and the ipsilateral EO during
exercises 1 and 2. As previous studies showed lower activity levels of these muscles during
exercises 1 and 2 [8, 40], these results raise doubts about the statement that this type of
exercise mainly activates the paraspinal muscles and not the abdominal muscles [8]. It was
suggested that the contralateral IO muscles were activated to maintain a neutral pelvis and
spine posture, in effect balancing the internal moments and lateral shear forces [8], but this
seems to occur in association with ipsilateral EO activity. In this way, the results of the
current study indicate that the abdominal obliques to create a stable unit accomplish an
ideal co-operation.
Also dorsally, there seems to be a co-operation between the ipsilateral and contralateral
back muscles. Recruitment patterns of the ipsilateral ICLL together with the contralateral
ICLT are recognized. This is consistent with the findings of Callaghan et al [8], although
that group reported lower activity levels concerning the contralateral MF.
The contralateral EO and the bilateral LD show moderate activity levels (10 to 20%
MVIC) during all exercises. In contrast to earlier findings [8], the results of the present
study show that extension of the upper extremity does not seem to influence the LD
muscle activity. In general, in contrast to its classification as a “global” muscle, symmetrical
activity is confirmed during all exercises. A possible reason for such equalized action of the
LD could be the tensioning of the TLF in a cranial direction, needed to control the trunk
irrespective of the movement or position of the upper limb.
32
Trunk and hip muscle activity during stabilization exercises in four-point kneeling
In exercise 3 there are moderate relative activity levels in both the contralateral IO and the
ipsilateral EO, and the difference between them is not significant. It seems as if the
contralateral IO and the ipsilateral EO can play a role in supporting the stable position to
control the neutral spine position. This can not be confirmed by earlier research, as some
researchers did not discriminate between ipsilateral and contralateral muscle activity [1, 40]
and others did not generalize to those terms because of varied results for the contralateral
IO [31]. The hip flexion that is added in exercise 3 in comparison to exercise 2 seems to
create a lower abdominal muscle activity (P ≤ 0.005, except for the ipsilateral IO).
The ICLL and ICLT seem to act together and also reach similar moderate activity levels
[8]. By the stretch the hip flexion in exercise 3 causes on the contralateral GM, this muscle
exhibits a significant higher muscle activity in exercise 3 in comparison to exercise 2 (P <
0.001). It seems that to counteract the more challenging body position by adding the hip
flexion, there is a compensation of the ipsilateral GM and ICLT and the contralateral MF.
The low-level symmetric activity of the RA throughout all exercises is confirmed by
previous studies [8, 40] and by studies of related exercises [6]. According to Callaghan et al.
[8] it indicates that this muscle was not functionally active and did not contribute to
stability. However, as the muscle is bilaterally active at a constant level during all exercises,
stability analysis (including external loads) is needed to assume that the limited activity is
irrelevant. In the current study the contralateral GM also seems to show relative low
activity levels during exercises 1 and 2. During all exercises (even on the side opposite to
the leg extension) the GM muscle is still active, preventing flexion of the hips and thus
preventing destabilization of the spine. The ipsilateral IO also creates a small relative
muscle activity.
Although a distinction is made between high, moderate and low relative muscle activity, the
electromyographic activity never exceeds 32% of MVIC. It is mentioned that useful
stabilization exercises for the clinic with the aim to hold and control the lumbar spine in a
neutral position, work the trunk muscles at approximately 30% of their maximum [25].
The results of this study show that in uncomplicated exercises in four-point kneeling
performed by healthy subjects, the investigated muscles seem to work together in a
harmonious way. These results tend to confirm the recent findings describing that, based
33
Chapter 1
on relative muscle activity, no single muscle appears to be superior in enhancing spine
stability, but as loads are applied to the spine there is an integration of the different muscles
in order to balance the stability and moment demands [26, 27]. However, the results of this
four-point kneeling position cannot be extrapolated to the erect posture, which is the usual
posture for the population being investigated.
It seems relevant that in the present study muscles are active in stabilization exercises that
are also strongly related to the main thoracolumbar fascia (TLF), such as the IO, EO, GM
and LD. Muscles like the ICLL, ICLT and MF have a hydraulic amplifier effect on the
different layers of the TLF. The posterior layer of the TLF is ideally positioned to regulate
tension via its extensive muscular attachments to both “local” and “global” muscles [5].
When loading the TLF for instance by the IO or EO, deformation and structural integrity
of the fascia should be protected by muscles like the LD and GM. The overall effect of
these muscles acting together could have a positive cascading effect on the stiffening of
both the lumbar spine and sacroiliac joint [44].
Based on the results of differences in cross-sectional area [12, 16] and timing [19, 22], there
may be some inhibition of certain muscles and dominance of other muscles [38] to
maintain a stable body position in LBP patients. The RA activity during flexion-extension
movements [39] and the EO activity during both flexion-extension [39] and left rotation
movements [34], as well as the muscle activity of the left thoracic erector spinae during
lateral flexion movements [28] were higher in LBP patients than in healthy controls.
However, during coordination and left rotation exercises the MF showed lower activity
levels in LBP patients than in healthy controls [11, 34]. So-called local muscles might
demonstrate lower and so-called global muscles higher activity levels in LBP patients
compared to healthy subjects. The present study, describing both local and global muscle
activity, provides a normative database which allows comparison with specific pain
populations in future research. Apart from the muscle activity levels, further integrated
research on muscle strength, muscle timing and movement patterns in specific LBP
populations is necessary to effectively distinguish between normal and abnormal spinal
function.
34
Trunk and hip muscle activity during stabilization exercises in four-point kneeling
CONCLUSION
Based on the harmonious way in which all trunk and hip muscles work together in
controlling the neutral spine position during these exercises in four-point kneeling, no
single muscle seems to be superior in enhancing spine stability, at least seen from the
perspective of muscle activity and not timing. Our study results indicate that both
“global and local” muscles function together to stabilize the spine, and this study
provides a normative database with which to compare specific pain populations in
future research.
Acknowledgements
The authors would like to thank Ms. Evelien De Burck and Ms. Wendy Van Loo for their
assistance in the collection of the data.
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stability of the lumbar spine. J Electrom Kinesiol 13:353-359
37
Chapter 1
33. Ng JK, Kippers V, Richardson CA (1998) Muscle fibre orientation of abdominal
muscles and suggested surface EMG electrode positions. Electromyogr Clin
Neurophysiol 38(1):51-58
34. Ng JK, Richardson CA, Parnianpour M et al (2002) EMG activity of trunk muscles
and torque output during isometric axial rotation exertion: a comparison between
back pain patients and matched controls. J Orthop Res 20(1):112-121
35. O'Sullivan PB (2000) Lumbar segmental ‘instability’: clinical presentation and specific
stabilizing exercise management. Man Ther 5(1):2-12
36. O’Sullivan PB, Twomey L, Alison GT (1997) Dynamic stabilization of the lumbar
spine. Crit Rev Phys Rehabil Med 9(3&4):315-330
37. Richardson CA, Jull GA (1995) Muscle control – pain control. What exercises would
you prescribe? Man Ther 1:2-10
38. Richardson C, Jull G, Hides J et al (1999) Therapeutic exercise for spinal stabilisation.
Scientific basis and practical techniques. Churchill Livingstone, Harcourt, London
39. Silfies SP, Squillante D, Maurer P et al (2005) Trunk muscle recruitment patterns in
specific chronic low back pain populations. Clin Biomech 20:465-473
40. Souza GM, Baker LL, Powers CM (2001) Electromyographic activity of selected trunk
muscles during dynamic spine stabilization exercises. Arch Phys Med Rehabil 82:15511557
41. Vera-Garcia FJ, Grenier SG, McGill SM (2000) Abdominal muscle response during
curl-ups on both stable and labile surfaces. Phys Ther 80(6):564-569
42. Vezina MJ, Hubley-Kozey CL (2000) Muscle activation in therapeutic exercises to
improve trunk stability. Arch Phys Med Rehabil 81:1370-1379
43. Vleeming A, Albert HB, van der Helm FCT et al (2004) Proceedings of the 5th
Interdisciplinary World Congress on Low back & pelvic pain, Melbourne, Nov p.14
44. Vleeming A, Pool-Goudzwaard AL, Stoeckart R et al (1995) The posterior layer of the
thoracolumbar fascia. Its function in load transfer from spine to legs. Spine 20(7):753758
38
CHAPTER 2
TRUNK MUSCLE ACTIVITY IN HEALTHY SUBJECTS DURING
BRIDGING STABILIZATION EXERCISES
Veerle K. Stevens, Katie G. Bouche, Nele N. Mahieu, Pascal L. Coorevits,
Guy G. Vanderstraeten, Lieven A. Danneels
Department of Rehabilitation Sciences and Physiotherapy; Faculty of Medicine and Health
Sciences, Ghent University, Ghent, Belgium.
BMC Musculoskeletal Disorders 2006;7:75
39
Chapter 2
ABSTRACT
Background
Trunk bridging exercises are often used as therapeutic exercises for lumbopelvic
stabilization. These exercises focus on the retraining of muscle coordination patterns in
which optimal ratios between local segmental stabilizing and global torque producing
muscle activity are assumed to be essential. However, a description of such ratios is lacking.
The purpose of this study was to investigate both relative (as a percentage of maximal
voluntary isometric contraction) muscle activity levels and ratios of local to global muscle
activity, during bridging stabilization exercises.
Methods
Thirty healthy university students (15 men, 15 women) with a mean age of 19.6 year
volunteered to perform 3 bridging exercises (single bridging, ball bridge and unilateral
bridging). The surface electromyographic activity of different trunk muscles was evaluated
on both sides.
Results
During all bridging exercises, the ratio of the internal oblique to the rectus abdominis was
very high due to minimal relative activity of the rectus abdominis. In general, the ratio of
the internal/external abdominal oblique activity was about 1. However, during the
unilateral bridging exercise, the ipsilateral internal/external abdominal oblique activity ratio
was 2.79 as a consequence of the significant higher relative activity of the internal oblique
compared to the external oblique. The relative muscle activity and the ratios of the back
muscles demonstrated similar activity levels for all back muscles, resulting in ratios about 1.
Conclusions
Both the minimal relative activity of the rectus abdominis and the high internal oblique to
the rectus abdominis activity ratio reported in the present study are in accordance with
results of other trunk stabilization exercises. The relative muscle activity and the ratio of
the abdominal obliques seem to alter depending on the task and the presumable need for
stability. The findings concerning the relative muscle activity and the ratios of the back
muscles support the assumption that during these bridging exercises, all back muscles
contribute in a similar way to control spine positions and movements in a healthy
population.
40
Trunk muscle activity during bridging stabilization exercises
BACKGROUND
Stability and movement are determined by the coordination of all the muscles that
surround the lumbar spine [1-3]. A strategy of trunk stiffening on one hand and creating
optimal movement on the other hand is assumed to be essential [1]. Within this context,
stabilization exercises are often used in clinical practice today. The main goal of
stabilization exercises is to protect spinal joint structures from further repetitive
microtrauma, recurrent pain and degenerative change [4]. Long term results of various
studies seem to indicate that specific lumbar stabilizing therapy as a single therapy or
combined with other treatments can reduce the intensity of the pain and disability in low
back pain (LBP) [5-8] and pelvic girdle pain patients [9-10] and prevent recurrent pain
episodes [11-13].
Debate exists on the anatomical classification of muscles in local and global muscles related
to specific functions, respectively segmental stabilizing (local) and torque producing and
providing general trunk stability (global), as proposed by Bergmark [14]. Some mentioned
that this classification is incorrect since no single muscle is superior at enhancing stability
[2,15,16]. In line with this, assessment of some “stabilization” exercises revealed that no
individual muscle could create an unstable situation when artificially reduced in activation
[15]. During stabilization training, Marshall & Murphy [17] aimed at minimizing rectus
abdominis (RA) activity in comparison with all other muscles of the lumbopelvic region. In
contrast, other researchers assumed that, once an optimal local activation has been
achieved, the interplay between local and global muscles is thought to be necessary [18,19].
To meet the different opinions, analysis of both so-called local and global muscles was
considered necessary. More than evaluation of differences between relative muscle activity
levels of local and global muscles, ratios of relative muscle activity were thought to provide
insight into the contribution of both muscle systems in relation to each other.
In the past, ratios of local to global muscle activity were only analysed in specific isolated
local muscle contraction tasks (abdominal drawing in manoeuvre) [20] and general
movement and isometric contraction activities (flexion, extension and lateral flexion from a
semiseated position in an apparatus) [21]. Recently, the ratio of the relative internal
abdominal oblique (IO) to rectus abdominis (RA) activity was reported in a small
41
Chapter 2
population performing core stability exercises on and off a swiss ball [17]. However, the
contribution of both local and global muscles calculated as a ratio was currently not
analysed in briding exercises.
The present study focused on 3 different bridging exercises often used early in a lumbar
stabilization training program. The supine posture with the knees and hips bent used
during bridging exercises, is to most LBP patients a comfortable, pain-free posture. From
this position limited movements, such as lifting the pelvis, can be started. In order to create
more functional tasks, limb movements can be added. By combining pelvis and leg
movements as used in exercise 3 in the present study, it is hypothesized that more global
muscle activity will be required to perform those more demanding tasks [15].
Exercise 2 in the present study was a ball bridge stabilization exercise. To amplify the
training effects of a bridging exercise and specifically challenge stability mechanisms, labile
surfaces such as gymnastic balls used to be advised [22,23]. However, recent research
evaluating bridging [24,25], other stabilization exercises [17,26] and trunk extension
exercises [27] could not support that the use of an exercise ball can create a greater
challenge for the musculoskeletal system or a training advantage in a healthy population.
The purpose of this study was to investigate the relative (% of maximal voluntary isometric
contraction) muscle activity and ratios of local to global muscle activity during single
bridging stabilization exercises, ball bridging exercises and bridging exercises with leg
movements.
METHODS
Subjects
Thirty healthy university students (15 men and 15 women) voluntary participated to the
study. Subjects had no history of neurological, respiratory or musculoskeletal back or
lower limb pathology. All subjects had an ‘average’ activity level, as determined by the
Dutch version of the habitual physical activity questionnaire [28]. They had a mean age of
19.6 (range:19-23) year, a mean height of 176.6 (range:157-194) cm and a weight of 66.9
42
Trunk muscle activity during bridging stabilization exercises
(range:42-84) kg. All subjects signed an informed consent. The subjects had no experience
with stabilization principles. The protocol was approved by the Ethics Committee of the
Ghent University Hospital.
Electromyography (EMG) preparation
Prior to the experimental phase, each subject was prepared for EMG recording as follows.
The skin was prepared by shaving excess hair and rubbing the skin with alcohol to reduce
impedance (typically ≤ 10 kOhm). Disposable Ag/AgCl surface electrodes (Bleu Sensor,
Medicotest GmbH, Germany) were attached parallel to the muscle fibre orientation,
bilaterally over the following so-called local trunk muscles: the inferior fibres of the IO
(midway between the anterior iliac spine and symphysis pubis, above the inguinal
ligament)[29,30], the lumbar multifidus (MF) (lateral to the midline of the body, above and
below a line connecting both posterior superior iliac spines)[31,32] and the lumbar part of
the iliocostalis lumborum (ICLL) (lateral to the vertical line through the posterior superior
iliac spine, above the iliac crest)[32]. The inferior fibres of the IO were considered to
represent local muscle activity [4,14] because it was shown that on the site medial and
inferior to the anterior superior iliac spine, the fibres of the transversus abdominus and the
IO are blended, so a distinction between the muscle signals cannot be made at this location
[33]. Concerning the back muscles, the MF and ICLL were so-called local muscles because
of their direct attachments to the vertebrae [4,14]. Because the RA, the external abdominal
oblique (EO) and the thoracic part of the iliocostalis lumborum (ICLT) transfer the load
directly between the thoracic cage and the pelvis, some call them global trunk muscles
[4,14]. The electrode placement of those global trunk muscles was as follows: the EO (15
cm lateral to the umbilicus)[22,29,30,34,35], the RA (3 cm lateral to the
umbilicus)[30,34,36,37] and the ICLT (above and below the L1 level, midway between the
midline and the lateral aspect of the body)[30,32]. The maximum interelectrode spacing
between the recording electrodes was 2.5 cm as recommended by Ng et al. [38], and each
electrode had an approximately 1.0 cm² pick-up area.
Maximal voluntary isometric contraction (MVIC) assessment
The MVICs of the muscles were measured in three trials before the experimental tasks.
These exercises were performed to provide a basis for EMG signal amplitude
normalization [30,34,35,39-43]. Normalization of EMG corresponding maximal EMG
43
Chapter 2
amplitude allows interindividual comparison to the individual maximum [44]. Failure to
normalize EMG data before quantitative analysis introduces confounding variables not
related to muscle function (for example skin impedance, electrode orientation and amount
of subcutaneous tissue) [44]. Five different isometric exercises against manual resistance
were executed. Verbal encouragement was given to ensure maximal effort. The maximal
activation of the abdominal obliques (IO and EO) was obtained by a combined flexionrotation exertion from a supported, straight-knee sitting position, with the hands placed
behind the head and the trunk held in a 45° angle. Manual resistance was applied to the
contralateral shoulder [30,39]. From the same sitting position the subject was asked to
perform a trunk flexion against bilateral manual resistance applied to both shoulders, for
the generation of the maximal isometric activity of the RA [39,43]. Concerning the MVICs
of the MF [29,30,34,42,43] and the lumbar and thoracic part of the iliocostalis lumborum
(ICLL and ICLT)[29,30,43] manual resistance was applied to the posterior aspect of the
scapula while the subject lay in the prone position, with the legs strapped to the table to
prevent them from moving. The subject was asked to perform a trunk extension.
Procedures and instrumentation
The subjects performed 3 experimental exercises, often used in clinical practice to train the
stability of the lower back. These exercises were executed in supine position, knees bent
(60° flexion) and feet on the floor. Exercise 1 was a single bridging exercise (figure 1),
exercise 2 a ball bridge exercise (figure 2) and exercise 3 a bridging exercise with extension
of the left or right leg (unilateral bridging exercise) (figure 3). Exercises 1 and 2 can be
called symmetric exercises and exercise 3 is an asymmetric exercise. After a detailed
explanation of each exercise, followed by a guided trial, the exercises were recorded. The
subjects lifted their pelvis until an angle of zero degrees hipflexion was reached. At the
beginning of each exercise a neutral lumbar spine position was determined by the examiner
(anterior and posterior iliac spines in line)[3] and the subject was encouraged to hold this
position during the course of the total exercise. To standardize the position of the subject
and the equipment, markers were placed on the floor. The exercises were executed in a
random sequence. The dynamic phases, lifting and lowering of the pelvis and the
extremities, lasted two seconds. The bridged positions in exercises 1 and 2 and the leg
extension in exercise 3 were hold for five seconds. The pace of 60 beats/min was set by a
44
Trunk muscle activity during bridging stabilization exercises
metronome. Three trials for every exercise were performed. A pause of at least 15 seconds
was allowed between the trials.
The raw surface EMG signals were bandpass-filtered between 10 and 500 Hz and amplified
using a differential amplifier (MyoSystem 1400, Noraxon Inc, Scottsdale, AZ). The overall
gain was 1000 and the common mode rate rejection ratio was 115 dB. The signals were
analogue/digitally (A/D) (12-bit resolution) converted at 1000 Hz and stored in a personal
computer.
Figure 1
Single bridging exercise (exercise 1)
Figure 2
Ball bridge exercise (exercise 2)
Figure 3
Unilateral bridging (exercise 3)
45
Chapter 2
Data analysis
The stored data were full-wave rectified and smoothed with a root mean square (RMS)
with a window of 150 milliseconds. For each of the muscles and for each testing session,
the RMS was calculated for the 3 repetitions of the different exercises. The mean RMS of
the three MVIC trials for every muscle was used to provide a basis for EMG signal
amplitude normalization of the data of the experimental exercises. The static phases of the
exercises were analysed, using an interval of 4700 ms after the defined starting point of the
holding position. Noraxon MyoResearch software 2.10 was used.
Not only the relative muscle activity of different trunk muscles, but also ratios of the
relative local abdominal muscle activity to the global abdominal muscle activity (IO/RA
and IO/EO) were calculated. In a similar way, ratios of the relative back muscle activity
(MF/ICLT and ICLL/ICLT) were determined.
Statistical analysis
Statistical analysis was performed using SPSS 12.0 software package (SPSS Inc., Chicago,
IL) for Windows. The level for statistical significance was set at α = 0.05. As there was no
significant difference between the muscle activity of the left and right muscles during
exercise 1 and 2, the mean activity levels were used. There were also no significant
differences between the muscle activity at the left side when performing a left leg extension
and the muscle activity at the right side when performing a right leg extension (exercise 3).
Therefore the mean value was used for further analysis and called ipsilateral muscle activity.
In accordance with the same findings on the other side, the new term contralateral muscle
activity was introduced. Concerning both the MVICs and the experimental exercises, an
analysis of variance for repeated measures was applied to evaluate the effects of the factor
muscle during every single exercise, separately for the abdominal and the back muscles.
Since the factor abdominal muscle was significant (p < 0.001) during all exercises and the
factor back muscle was significant (p = 0.02) during the ball bridge exercise, post-hoc least
significance difference tests (LSD), adjusted by a Bonferroni test to protect against type I
errors, were used to analyze the significant differences between the individual muscles in
each exercise. Descriptive statistics showed the relative abdominal and back muscle activity
ratios.
46
Trunk muscle activity during bridging stabilization exercises
RESULTS
The mean EMG amplitudes of the different abdominal and back muscles during the 3
bridging exercises are presented in Table 1. Since particularly the contribution of the local
muscle activity compared to global muscle activity is concerned, the analysis of the
abdominal muscle activity is performed separately from the analysis of the back muscle
activity.
Concerning the abdominal muscles, during all exercises, the relative activity of the RA was
significantly lower than the relative activity of the obliques (p < 0.001). During the single
bridging exercise 1, the muscle activity of the obliques did not differ significantly (p =
1.00). In contrast, during the ball bridge exercise 2, the EO showed significantly higher
activity levels than the IO (p = 0.003). During exercise 3, the contralateral EO activity was
also significantly higher than the contralateral IO activity (p = 0.007), but the ipsilateral EO
activity was significantly lower than the ipsilateral IO activity (p < 0.001).
Regarding the back muscles, except for the ICLL, which showed significant higher activity
than the ICLT during the ball bridge exercise 2 (p = 0.01), the activity levels did not differ
significantly (p ≥ 0.26).
Table 1: Mean relative muscle activity (% of MVIC) and standard deviation (SD) of the different
trunk muscles during bridging exercises.
IO
RA
EO
MF
ICLL
ICLT
Mean (SD) Mean (SD) Mean (SD) Mean (SD) Mean (SD) Mean (SD)
Exercise 1
Exercise 2
Exercise 3
5.58
(5.00)
1.91
(1.27)
5.98
(4.36)
22.64
(7.51)
20.32
(8.56)
20.59
(5.51)
6.58
(4.80)
2.76
(2.35)
10.32
(7.99)
23.99
(7.15)
27.17
(10.20)
22.24
(6.96)
Ipsilateral
29.80
(9.97)
4.72
(3.45)
16.34
(12.09)
23.54
(6.33)
28.45
(11.50)
25.84
(7.84)
Contralateral
10.11
(6.95)
3.55
(2.18)
14.93
(9.34)
24.58
(8.80)
20.44
(9.24)
20.60
(8.22)
IO = internal oblique; MF = lumbar multifidus; ICLL = iliocostalis lumborum pars lumborum; RA = rectus
abdominis; EO = external oblique; ICLT = iliocostalis lumborum pars thoracis.
To emphasize the relation between so-called local segmental stabilizing muscles and global
torque producing muscles, the relative activity was expressed as ratios. The mean ratios are
presented in figures 4 and 5.
In general, the ratio of the local to the global muscle activity was about 1.
47
Chapter 2
The IO/RA ratio was much higher than 1 during all exercises (3.00 in exercise 1 and 2.96
in exercise 2). During exercise 3, the ipsilateral IO/RA was 7.95 and the contralateral
IO/RA was 3.16. The ipsilateral IO/EO was higher during exercise 3 (2.79).
The MVICs were used to normalize the EMG values obtained during the experimental
exercises. The mean EMG amplitudes and standard deviations (SD) are presented in Table
2. The MVICs of the back muscles did not differ significantly (p ≥ 0.60). Except for the
significant higher MVIC of the RA in comparison with the MVIC of the IO and EO (p ≤
0.01), the abdominal muscles did not show significant different amplitudes (p = 1.00).
12
11
10
Relative muscle activity ratio
9
Exercise 1
Exercise 2
8
7
6
5
4
3
2
1
0
IO/RA
IO/EO
MF/ICLT
ICLL/ICLT
Ratio
Figure 4
Mean ratios and SD of relative local muscle activity to relative global trunk muscle activity during
the single bridging (exercise 1) and ball bridge exercise (exercise 2). IO = internal oblique; MF =
lumbar multifidus; ICLL = iliocostalis lumborum pars lumborum; RA = rectus abdominis; EO = external
oblique; ICLT = iliocostalis lumborum pars thoracis.
48
Trunk muscle activity during bridging stabilization exercises
12
11
10
Relative muscle activity ratio
9
Ipsilateral
8
Contralateral
7
6
5
4
3
2
1
0
IO/RA
IO/EO
MF/ICLT
ICLL/ICLT
Ratio
Figure 5
Mean ratios and SD of relative local muscle activity to relative global trunk muscle activity during
the unilateral bridging exercise (exercise 3). IO = internal oblique; MF = lumbar multifidus; ICLL =
iliocostalis lumborum pars lumborum; RA = rectus abdominis; EO = external oblique; ICLT = iliocostalis
lumborum pars thoracis.
DISCUSSION
The purpose of the current study was to evaluate the muscle activity during commonly
used bridging stabilization exercises. The investigated exercises are supposed to be
beneficial to stabilize the lumbar spine region. When describing exercise therapy, it is
important to understand the muscle activity in healthy conditions. In the current study the
muscle activity is expressed as relative (as a percentage of MVIC) EMG as well as ratios of
relative activity. The description of differences in activation patterns of so-called local and
global muscles can be made more sensitive by calculating ratios than using isolated relative
muscle activity levels [20]. Some researchers and clinicians assume that optimal stabilization
of the lower back during basic stabilization exercises may be created by a good activation
of the local muscles [4,19,45-47]. In this respect, the way the local muscle activity is related
to the global muscle activity can be assumed more important than the relative muscle
49
Chapter 2
activity levels of the muscles separately. For interpretation purposes, the results of both the
relative EMG activity and the ratios of relative activity are integrated.
Table 2: Mean EMG activity (Mean) and standard deviation (SD) of the maximal voluntary
isometric contractions.
Mean
(SD)
IO
184.78
(82.94)
RA
275.96
(132.06)
EO
191.50
(136.74)
MF
264.23
(114.93)
ICLL
254.17
(147.80)
ICLT
240.63
(106.78)
IO = internal oblique; MF = lumbar multifidus; ICLL = iliocostalis lumborum pars lumborum; RA =
rectus abdominis; EO = external oblique; ICLT = iliocostalis lumborum pars thoracis.
Concerning the abdominal muscles, during all bridging exercises, the relative activity of the
RA was significantly lower than the relative muscle activity of the obliques. One of the
consequences of this low relative RA activity was that during all exercises, the IO/RA ratio
demonstrated the highest values compared to the other abdominal and back muscle activity
ratios. However, these findings need to be interpreted with caution, since normalization of
the EMG data of the experimental exercises occurred using MVICs and the RA MVIC
amplitude was significantly higher in comparison with the MVIC amplitudes of the
abdominal obliques. Nevertheless, the consistent low-level activity of the RA was in
accordance with the findings of similar research [36,48] and research of related exercises
[39]. These studies also used MVIC normalization procedures, but did not report the
MVIC values nor analysis performed on these data.
The small relative muscle activity levels reported in the present and the latter studies were
not necessarily related to a nonstabilizing capacity of this muscle. Only small activity levels
seem to be necessary to ensure sufficient stability in a neutral spine posture in nonweightbearing positions [40]. Generally for most tasks of daily living very modest levels of
abdominal wall co-contraction are sufficient [2]. Cholewicki et al. [40] highlighted the
50
Trunk muscle activity during bridging stabilization exercises
importance of motor control to coordinate muscle recruitment between so-called global
and local muscles during functional activities to ensure mechanical stability is maintained.
Under such conditions they suggested that intersegmental muscle activity as low as 1 to 3
% MVC may be sufficient to ensure dynamic stability [40]. Furthermore, biomechanical
modelling is needed to draw conclusions about stability contributions as stability is also
proportional to the square of the muscle’s moment arm.
The objective for the use of the ratio of IO/RA activity in the present study, was to
enhance the understanding of the co-activation of both local and global muscles during this
kind of stabilization exercises. Other researchers stated that analysis of the IO/RA ratio is
important to verify if the activity of the RA is minimal in comparison with all other
muscles of the lumbopelvic region to fulfil the requirement for a good stabilization exercise
[17]. In our opinion, respecting adequate activation levels depending on the demands
during different tasks is essential, rather than aiming at minimal activity of certain muscles.
Ratios assist in providing further insight in the co-operation of the different muscles during
various tasks.
During the ball bridge exercise, the EO showed significantly higher relative EMG than the
IO. Consequently, the IO/EO ratio was low (< 1) during this exercise. In accordance with
these results, McGill [1] assumed that the EO may have a greater potential in stabilizing the
trunk than the local abdominal muscles. Vera-Garcia et al. [29] found that when
performing curl-ups on a gymnastic ball, there was much more co-contraction of the EO
muscle with the RA muscle when compared to other tasks because of the greatest
possibility of rolling laterally off the ball. In order to enhance this stability, it appears that
the motor control system selects to increase EO activity more than the other abdominal
muscles. However, recent research evaluating bridging exercises showed no significant
differences in relative EO and RA activity between performance on firm or ball surfaces
[24,25]. Debate exists on increased [24] or unchanged IO activity [25] during ball bridge
exercises. However, the ball bridge exercises described in the latter studies were performed
with the feet flat on the ball, in contrast to the calf position on the ball in the present study.
Although only the calfs were positioned on the ball, the global torque producing EO might
be activated more than the local segmental stabilizing IO to prevent the limbs from rolling
of the ball and jepardizing the trunk stability. Analysis of the relative EMG activity levels
51
Chapter 2
showed a greater increase in EO activity compared to IO activity between the single
bridging and the ball bridge exercise. This could explain the small ratio of the IO to EO
during the ball bridge exercise in the current study.
During the unilateral bridging exercise, the ipsilateral IO showed significantly higher EMG
than the ipsilateral EO and the contralateral IO demonstrated significantly lower activity
than the contralateral EO. Consequently, the contralateral IO/EO ratio was low (< 1) and
the ipsilateral IO/EO ratio was higher than 2 during this exercise 3. Kavcic et al. [15]
reported that during single and unilateral bridging exercises the IO and EO seem to
demonstrate consistently a large impact on induced increasing and decreasing stability.
Both so-called local and global oblique muscles seem to work together and may have an
important role in controlling the neutral spine position during this exercise. When the
contralateral leg is raised, a rotational moment about the spine is expected to occur. The
ipsilateral IO can cause an ipsilateral rotational moment about the spine and the ipsilateral
EO can create a moment in the opposite direction to counter the spine moment. To stop
the spine from twisting, appropriate muscle activity may generate stability. The ratio of the
IO to EO activity seems to depend on the task and the presumable need for stability.
Regarding the back muscles, in general, the relative muscle activity levels of the local and
global muscle system were not significantly different. All ratios of relative back muscle
activity were about 1. Van Dieën et al. [21] reported ratios of the lumbar to the thoracic
erector spinae (ES) muscles, representing local to global muscle activity, varying from 0.5
to 0.9 in healthy subjects during global exercises in a semi-seated posture. Maximal
isometric extension exercises seemed to create a lumbar ES/ thoracic ES ratio of 1.1 [21].
This demonstrates that during different tasks and exercises, all back muscles contribute in a
similar way to control spine positions and movements. These findings support the
statement that no single muscle seems superior to another and that all muscles act together
in the same way to create a stable position of the spine during this kind of exercises
[2,15,16].
Only during the ball bridge exercise, the ICLL showed significantly higher activity than the
ICLT. In the past, application of unstable surfaces such as a ball was supposed to increase
muscle activity [29]. Since the ICLL is located closer to the centre of rotation than the
ICLT, the increasing effect might be higher. However, recent research comparing exercise
52
Trunk muscle activity during bridging stabilization exercises
surfaces in stabilization and trunk extension exercises, demonstrated that the addition of a
ball did not influence [17,24-27] or even decreased back muscle activity [27]. In the present
study, the ratio ICLL/ICLT remained about 1.
Though the data on the ratios of local to global relative muscle activity were normally
distributed, relatively large SDs were noticed concerning the abdominal muscles. These
findings represent abdominal ratios spread apart and a relatively flat bell curve, indicating
that relatively more subjects showed ratios towards one extreme or the other. Since the
mean relative abdominal muscle activity ratios discussed in the present study were
supposed to be confined by the spread values, interpretation might be influenced.
LBP patients might demonstrate different recruitment patterns, for instance higher or
lower muscle activity due to pain adaptation or spasm caused by pain [49]. Within this
context, the current preliminary data may provide a foundation to help determining
exercise treatment approaches intended to recruit specific muscle sites.
CONCLUSIONS
To enhance the understanding of the trunk muscle recruitment patterns during stabilization
exercises often used in clinical practice, relative EMG activity as well as ratios of muscle
activity of both local and global muscles seem important. The present study shows that the
abdominal muscle activity ratios IO/RA and IO/EO demonstrate a different pattern.
During all exercises, the IO/RA ratio is very high due to minimal RA activity. The relative
muscle activity and the ratio of the abdominal obliques seem to alter depending on the task
and the presumable need for stability. The findings concerning the relative muscle activity
and the ratios of the back muscles support the assumption that during these bridging
exercises, all back muscles contribute in a similar way to control spine positions and
movements in a healthy population.
Acknowledgements
The authors thank Ms. Evelien De Burck and Ms. Wendy Van Loo for their assistance in
collecting the data.
53
Chapter 2
REFERENCES
1.
McGill SM: Low back disorders: evidence based prevention and rehabilitation.
Edited by Human Kinetics Publishers, Champaign, III; 2002.
2.
McGill S, Grenier S, Kavcic N, Cholewicki J: Coordination of muscle activity to
assure stability of the lumbar spine. J Electromyogr Kinesiol 2003, 13(4):353-359.
3.
Richardson CA, Jull GA: Muscle control – pain control. What exercises would
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58
CHAPTER 3
THE INFLUENCE OF SPECIFIC TRAINING ON TRUNK
MUSCLE RECRUITMENT PATTERNS IN HEALTHY SUBJECTS
DURING STABILIZATION EXERCISES
Veerle K. Stevens, Pascal L. Coorevits, Katie G. Bouche, Nele N. Mahieu,
Guy G. Vanderstraeten, Lieven A. Danneels
Department of Rehabilitation Sciences and Physical Therapy; Faculty of Medicine and
Health Sciences, Ghent University, Ghent, Belgium.
Manual Therapy, In Press
59
Chapter 3
ABSTRACT
Low back pain is a major problem involving high medical costs, therefore effective
prevention strategies are essential. Stabilization exercises seem to facilitate the
neuromuscular control of the lumbar spine and may be useful in prevention programs. To
investigate whether specific lumbar stabilization training has an effect on muscle
recruitment patterns in a healthy population, in the present study 30 subjects were recruited
to perform two types of testing exercises, i.e. bridging exercises and exercises in four-point
kneeling, both before and after training. Surface electromyographic data of different
abdominal and back muscles were obtained. After training, analysis of the relative muscle
activity levels (percentage of maximal voluntary isometric contraction) showed a higher
activity of the local (segmental-stabilizing) abdominal muscles, but not of the local back
muscles; minimal changes in global (torque-producing) muscle activity also occurred.
Analysis of the local/global relative muscle activity ratios revealed higher ratios during all
exercises after training, although not all differences were significant. These results indicate
that muscle recruitment patterns can be changed in healthy subjects by means of a training
program that focuses on neuromuscular control. Additional studies are needed to evaluate
this type of training as a prevention strategy.
KEY WORDS
Stabilization exercise – Prevention – Lumbar stabilization training – Surface
electromyography
60
Influence of specific training on trunk muscle recruitment during stabilization exercises
1. INTRODUCTION
In 1994 52% of Belgian hospital nurses reported musculoskeletal job-related problems that
lasted longer than 1 day; low back pain (LBP) was the major cause (53.3%) (Clarijs et al.,
1998). Effective primary and secondary prevention strategies are needed to address this
problem because the costs for e.g. health insurance, employers and society, as well as the
reduced quality-of-life of the patients, are substantial.
Short- and long-term results indicate that specific lumbar stabilizing therapy can decrease
the number of recurrent pain episodes (Hides et al., 2001) and recurrent treatment periods
(O’Sullivan et al., 1997; Rasmussen-Barr et al., 2003). Specific lumbar-stabilizing therapy
involves changing muscle recruitment patterns. Symptomatic chronic LBP patients with
clinical evidence of spondylolysis or spondylolisthesis were shown to be able to activate the
deep abdominal muscles without significant co-activation of the rectus abdominis muscle
(RA) when performing an abdominal drawing-in manoeuvre after a 10-week intervention
(O’Sullivan et al., 1998). Lumbar stabilization training that paid no specific attention to the
local muscles showed no changes in relative electromyographic (EMG) amplitudes during
more complex stabilization exercises after 12 weeks of training (Arokoski et al., 2004).
Apart from these studies on patients, the effect of stabilization training has not yet been
investigated in a healthy population in relation to primary prevention.
Local muscles of the trunk, such as the lumbar multifidus (MF), with their vertebrae to
vertebrae attachments (as described by Macintosh & Bogduk, 1987), are supposed to
control the fine-tuning of the positions of adjacent vertebrae (segmental stabilization)
(Bergmark, 1989; Richardson et al., 1999; Hodges and Moseley, 2003). Because of their
connection through the thoracolumbar fascia, the transversus abdominis (TA) and the
inferior fibres of the internal oblique (IO) also have direct attachment to the lumbar
vertebrae and can therefore also be considered as local muscles (Hodges, 1999).
Unlike the local muscles, the global muscles are supposed to be important for torque
production and general trunk stability, because they are not directly attached to the spine
(Bergmark 1989). The global muscle system includes the RA, the external oblique (EO), the
gluteus maximus, the latissimus dorsi and the thoracic part of the iliocostalis lumborum
muscles (ICLT) (Richardson et al., 1999).
To train functional stability, once an optimal local activation has been achieved, the
interplay between local and global muscles is thought to be necessary (Hodges and
61
Chapter 3
Moseley, 2003; Richardson et al., 2004). Because biomechanical and muscle research has
shown no clear distinction between the contribution of the local and global muscles to
spine stability, this functional classification based on anatomic findings needs to be
considered with some caution (Arokoski et al., 2001; Cholewicki and Van Vliet, 2002;
Kavcic et al., 2004a; Stevens et al., 2006). Not only is the local muscle system important,
but also the controlled co-operation between the two muscle systems can provide a stable
structure. Consequently, the ratio of the local muscle activity to the global muscle activity
needs to be further elucidated. According to Edgerton et al. (1996) EMG ratios can be a
sensitive discriminator of altered recruitment patterns and muscle dysfunction. In order to
highlight differences in the synergistic activity of local versus global muscles (e.g. IO versus
RA; lumbar versus thoracic erector spinae muscles), ratios of muscle activity levels during
various stabilization exercises have been investigated in healthy subjects (Marshall and
Murphy, 2005) and in LBP patients (O’Sullivan et al., 1998; van Dieën et al., 2003).
The purpose of the current study was to evaluate the benefit derived from specific
stabilization training for a prevention program by investigating whether this training had an
effect on muscle recruitment patterns in healthy subjects. The training was an isolated local
muscle contraction (first phase) followed by integrating local co-contraction in different
movements starting from various positions. The exercises used for the evaluation were
bridging exercises and exercises in four-point kneeling, both of which are often used in
clinical practice to train lumbar stability. The specific attention paid to the local muscles
during the intervention aimed to increase local muscle activity and consequently change the
local/global ratio.
2. METHODS
2.1. Study design
This was a cross-sectional study. The baseline EMG test session was followed by a 3month intervention period and then a second EMG test session.
2.2. Subjects
Thirty healthy subjects (15 men and women) voluntarily participated in this study. Their
mean age was 19.6 (range 19-23) years, mean height was 176.5 (range 157-194) cm and
62
Influence of specific training on trunk muscle recruitment during stabilization exercises
mean weight was 66.9 (range 42-84) kg. All subjects gave written informed consent. The
study was approved by the Ghent University Ethics Committee.
2.3. Procedures
2.3.1. Intervention period
The two EMG test sessions were separated by an intervention period of three months. The
subjects were instructed in accordance with the principles often used in training lumbar
stability (Richardson and Jull, 1995; Richardson et al., 1999; O’Sullivan, 2000). Instruction
in the basic anatomy of the TA, MF and other abdominal and back muscles was aimed at
emphasising the difference between the local and global trunk muscles and to help avoid
‘substitution’ strategies of the global muscles. In the first phase of the training, local muscle
activity was facilitated without substitution strategies of the global muscles and with focus
on the continuation of normal breathing during the exercises. Subsequently, the time for
holding the position and the number of repetitions were increased, and different postures
(supine, four-point kneeling, prone, sitting and standing) were added (Richardson et al.,
1999). Once an accurate and sustained contraction of the local muscles was achieved in
different postures (10 contractions with 10-s holds), the exercises progressed to the second
phase which involved applying low load to the muscles through controlled movements of
the upper and lower extremities (Richardson and Jull, 1995). The aim during the third
phase was to integrate the motor skill into normal static tasks and dynamic functional tasks
(Richardson et al., 1999). During the 3-month intervention period, eight guided training
sessions took place, each lasting 30 min; the subjects were also asked to perform the
exercises for about 15 min each day at home as part of the intervention. During the
intervention period, no specific attention was paid to the exercises performed in the test
sessions.
2.3.2. Test sessions
Before and after the specific stabilization training, the subjects performed two types of
testing exercises: bridging exercises and exercises in four-point kneeling. For both, the only
instruction given during the testing was to maintain the lumbar neutral spine position. At
the moment of the first test session, the subjects had no knowledge or experience of
stabilization principles.
63
Chapter 3
2.4. Equipment and measurements
2.4.1. Electromyography
The skin was prepared by shaving excess hair and rubbing the skin with alcohol to reduce
impedance (typically ≤ 10 kΩ). Disposable Ag/AgCl surface electrodes (Blue Sensor,
Medicotest A/S, Ølstykke, Denmark) were attached parallel to the muscle-fibre orientation,
as described previously (Danneels et al., 2001b, 2002), bilaterally over the following socalled local trunk muscles: the inferior fibres of the IO (midway between the anterior iliac
spine and symphysis pubis, above the inguinal ligament) and the lumbar MF (lateral to the
midline of the body, above and below a line connecting both posterior superior iliac
spines). Although the focus of stabilization training was on the TA, it was expected that
this would be reflected in the surface EMG of the inferior fibres of the IO. Marshall &
Murphy (2003) showed that medially and inferiorly to the anterior superior iliac spine, the
fibres of the TA and IO are blended, so that a distinction between the muscle signals
cannot be made at this location; also, at this site the direction of the fascicles of both
muscles is similar (inferomedial) (Urquhart et al., 2005). Moreover, both the TA and the
inferior fibres of the IO play a similar role in compressing the sacroiliac joint and
consequently increasing the control of that region (Richardson et al., 2002).
The selected so-called global trunk muscles were the EO (15 cm lateral to the umbilicus),
the RA (3 cm lateral to the umbilicus), and the ICLT (above and below the L1 level,
midway between the midline and the lateral aspect of the body). The maximal interelectrode spacing between the recording electrodes was 2.5 cm as recommended by Ng et
al. (1998), and each electrode had a pick-up area of approximately 1.0 cm². To reduce the
variability due to the electrode position, a personalized template ensured the exact
reapplication of the electrodes (Danneels et al., 2001a).
2.4.2. Exercises during the test procedure
Maximal voluntary isometric contractions (MVIC) of the muscles were measured before
the experimental tasks. These exercises were performed to provide a basis for EMG signal
amplitude normalization. Three different isometric exercises against manual resistance were
performed according to the description of Danneels et al. (2001b), and each exercise was
registered three times during 3 s.
After the MVICs, the subjects were asked to start the experimental exercises. Six exercises
(often used in clinical practice to train lumbar stability) were performed. The first group of
64
Influence of specific training on trunk muscle recruitment during stabilization exercises
exercises was executed in supine position, knees bent (60° flexion) and feet on the floor. A
bridging exercise, either simple or accompanied by leg movements, was performed
(exercises 1 - 3 in Table 1). The second group of exercises was performed in four-point
kneeling (exercises 4 - 6 in Table 1). At the start of each exercise, the examiner determined
the subject’s lumbar neutral spine position and the subjects were asked to hold this
position throughout the exercise. In four-point kneeling, the neutral spine position was set
about halfway between full extension and a flat spine (Danneels et al., 2002); in supine
position the anterior and posterior superior iliac spines were in line (Richardson et al.,
2004). The exercises were performed in a random sequence. In order to standardize the
position of the subject and the equipment, markers were placed on the floor. The dynamic
phases (i.e. lifting and lowering of the pelvis and the extremities) lasted 2 s. The mid-phase
(i.e. extended leg/arm and lifted pelvis) was held for 5 s. The rhythm of 60 beats/min was
set by a metronome. For each exercise three trials were performed. To prevent muscular
fatigue, an interval of at least 15 s was allowed between the exercises; during these periods
the exercises were explained.
Before the second test session, an ultrasound (US) evaluation was carried out to assess
whether the subjects could produce an isolated contraction of the TA. In a clinical setting
the tonic contraction of the MF is easy to palpate, but the difference between contraction
of the IO and the TA is not always easy to detect. Therefore, the subjects were placed in a
supine position lying crooked, and were then asked to draw in their lower abdomen slowly
and gently, without moving the spine. The transducer was placed on the anterolateral
aspect of the abdominal wall, at the level of the umbilicus. A Siemens Sonoline SL-1
ultrasound imaging device was used with a linear array probe with a wave frequency of 7.5
MHz. The criterion was a slow and controlled tensioning of the anterior fascial attachment
of the TA in a lateral direction. The TA was slightly thickened and the IO and EO
remained relatively inactive (Richardson et al., 2004). Because the aim was to evaluate the
effect of training local muscle co-contraction on the performance of stabilization exercises,
this additional US evaluation was useful to understand the reasons for changes in EMG
activity. This US study revealed that 5 subjects were not able to contract the TA in isolation
from the global muscle system and were thus excluded.
65
Chapter 3
Table 1
Exercises
Group 1
Bridging in supine position
Exercise 1
Bridging in supine position
Exercise 2
Ball bridge
Exercise 3
Unilateral bridging: bridging with extension of the left/right leg
Group 2
Four-point kneeling
Exercise 4
Single-leg lift, performed by extending the left/right leg out to the horizontal and
returning it to the starting position
Exercise 5
The leg extension of exercise 4 coupled with the simultaneous raising of the contralateral
arm to the horizontal before returning the extended leg and arm to the original position
Exercise 6
This exercise is basically the same as exercise 5, but with the addition of moving the
trunk/pelvis in a backward direction (i.e. away from the hands), which increases the angle
of hip flexion of the loaded leg by 30°
2.5. Data analysis
The raw surface EMG signals were measured at a bandwidth of 10 - 500 Hz, using a
differential amplifier (MyoSystem 1400, Noraxon Inc, Scottsdale, USA). The overall gain
was 1000 and the common mode rate rejection ratio was 115 dB. The signals were
analogue/digitally (A/D) (12-bit resolution) converted at 1000 Hz and stored in a personal
computer. The stored data were full-wave rectified and smoothed with a root mean square
(RMS) with a window of 150 millis. For each of the muscles and for each testing session,
the RMS was calculated for the 3 repetitions of the different exercises. The mean RMS of
the three MVIC trials for every muscle was used to provide a basis for EMG signal
amplitude normalization of the data of the exercises. The static phases of the exercises
were analysed using an interval of 4700 ms after the defined starting point of the holding
position. Noraxon MyoResearch software 2.10 was used for these analyses.
The effect on muscle recruitment patterns was investigated in two ways. First, the changes
in muscle activity of each muscle as a result of the training were investigated. Second, the
difference in the ratio of local muscle activity to global muscle activity (separately for
abdominal and back muscles) before and after training was evaluated. This assessment was
based on two ratios of the abdominal muscles (the IO/RA and the IO/EO) and one of the
back muscles (the MF/ICLT).
2.6. Statistical analysis
Statistical analysis was performed using the SPSS 11.0 software package (SPSS Inc.,
Chicago, IL) for Windows. Given the symmetry of the task during the single-bridging and
66
Influence of specific training on trunk muscle recruitment during stabilization exercises
the ball-bridging exercise (P ≥0.1), the EMG values of the muscles of the left and the right
side were averaged. Because there were no significant differences (P >0.05) between the
ipsilateral and contralateral muscle activity values during the asymmetric bridging exercises,
they were also averaged. Ipsilateral referred to the side of the extended leg and contralateral
to the other side.
A multivariate analysis of variance (MANOVA) was used to evaluate the changes in muscle
activity as a result of specific stabilization training (factors muscle [5 muscles], time [before
and after training], and side [only in the asymmetric exercises]). In the event of several
significant interactions, least significance difference tests, adjusted by a (although
conservative) Bonferroni test to protect against type I errors, were used to analyze the
significant differences between the individual muscles in each exercise. Consequently, the
level for statistical significance was set at α = 0.002 for exercises 1 to 4 (two-factor
interaction) and at α = 0.0008 for exercises 5 and 6 (three-factor interaction).
To analyse the difference in the ratio of local muscle activity to global muscle activity
before and after training, paired sample t-tests were used and α was set at 0.05.
3. RESULTS
3.1. Changes in relative muscle activity
Figures 1 to 3 present the relative pre- and post-training EMG levels (% MVIC) of the
different muscles and their respective P -values.
3.1.1. Local muscle activity
After training, the local IO showed a significantly higher relative muscle activity (P ≤0.001)
during all the bridging exercises. In contrast to the bilateral changes of the local IO during
the bridging exercises, after training only the relative muscle activity of the ipsilateral IO
increased significantly during the asymmetric four-point kneeling exercise 5 (P ≤0.001) and
exercise 6 (P = 0.001).
3.1.2. Global muscle activity
After training, during the symmetric exercises 1 and 2 the relative muscle activity of the
global RA was also significantly higher (P ≤0.001).
67
Chapter 3
For the global EO and the local and global back muscles, no significant differences
between the EMG levels before and after training were found for any of the exercises.
70
Relative muscle activity (% MVIC)
60
50
< 0.001
Ex 1 - Pre
40
0.19
< 0.001
Ex 1 - Post
0.81
Ex 2 - Pre
0.63
30
Ex 2 - Post
0.01
0.93
20
0.26
10
0.001
0.001
0
IO
MF
RA
EO
ICLT
Muscle
Fig. 1. Mean values, SD and P-values (between pre- and post-training for each exercise) of the relative EMG
activity during the symmetric exercises (α = 0.002). Ex, exercise; Pre, before training; Post, after training;
MVIC, maximal voluntary isometric contraction; IO, internal oblique; MF, lumbar multifidus; RA, rectus
abdominis; EO, external oblique; ICLT, iliocostalis lumborum pars thoracis.
70
< 0.001
60
Relative muscle activity (% MVIC)
0.39
50
Ex 3 - Pre
Ex 3 - Post
0.29
0.11
40
0.38
0.91
Ex 4 - Pre
0.02
0.38
0.007
0.11
0.007
0.003
< 0.001
30
Ex 4 - Post
Ex 5 - Pre
Ex 5 - Post
0.93
Ex 6 - Pre
0.001
0.06
Ex 6 - Post
20
0.005
10
0.02
0.06
0.03
0
IO
MF
RA
EO
ICLT
Muscle
Fig. 2. Mean values, SD and P-values (between pre- and post-training for each exercise) of the ipsilateral
relative EMG activity during the asymmetric exercises (α = 0.002 in exercises 3 and 4; α = 0.0008 in exercises
5 and 6). Ex, exercise; Pre, before training; Post, after training; MVIC, maximal voluntary isometric
contraction; IO, internal oblique; MF, lumbar multifidus; RA, rectus abdominis; EO, external oblique; ICLT,
iliocostalis lumborum pars thoracis.
68
Influence of specific training on trunk muscle recruitment during stabilization exercises
3.2. Changes in ratios
Because co-operation between the local and global muscle systems is particularly important
in creating a stable structure, changes in the local/global muscle activity ratio after
stabilization training were also evaluated. To detect changes in this ratio, paired sample ttests were used; the level for statistical significance was set at α = 0.05.
After training, the ratio of the local to global muscle activity was higher in all exercises
(Table 2). However, not in all exercises the increase in the IO/RA and the MF/ICLT ratios
was significant. All ratios were significantly higher (P ≤0.01) in the single bridging exercise
(exercise 1). In the ball bridge exercise (exercise 2) a significant difference (P ≤0.001) was
found for the abdominal muscles (IO/RA ratio and IO/EO ratio), but not for the back
muscles (MF/ICLT ratio). In the unilateral bridging exercise (exercise 3), the difference
between the ratios before and after training was significant (P ≤0.02), except for the
MF/ICLT ratio and the ipsilateral IO/RA ratio. In the exercises in four-point kneeling
(exercises 4 - 6), the difference in the ratio local to global muscles before and after training
was significant (P ≤ 0.05) only for the ipsilateral muscles. However, the ratio of the
contralateral oblique abdominal muscles also increased significantly (P = 0.04) in exercise 5.
70
0.05
60
0.007
Relative muscle activity (% MVIC)
50
0.43
Ex 3 - Pre
0.29
40
0.44
0.45
0.52
Ex 4 - Pre
Ex 4 - Post
Ex 5 - Pre
0.05
028
30
Ex 3 - Post
0.09
0.001
0.01
Ex 5 - Post
0.06
0.38
Ex 6 - Pre
0.07
Ex 6 - Post
0.41
20
0.02
10
0.01
0.10
0.03
0
IO
F
MF
RA
EO
ICLT
Muscle
Fig. 3. Mean values, SD and P-values (between pre- and post-training for each exercise) of the contralateral
relative EMG activity during the asymmetric exercises (α = 0.002 in exercises 3 and 4; α = 0.0008 in exercises
5 and 6). Ex, exercise; Pre, before training; Post, after training; MVIC, maximal voluntary isometric
contraction; IO, internal oblique; MF, lumbar multifidus; RA, rectus abdominis; EO, external oblique; ICLT,
iliocostalis lumborum pars thoracis.
69
Chapter 3
4. DISCUSSION
4.1. Changes in relative muscle activity
Stabilization training involves isolated local muscle contraction and an integration of the
local and global muscle systems during particular movement patterns (O’Sullivan, 2000). It
was thought that such training with specific attention paid to the TA and MF (Richardson
et. al., 1999; O’Sullivan, 2000) would significantly increase the relative muscle activity of the
local muscles in healthy subjects.
4.1.1. Local muscle activity
The results of the present study indicate that, since the relative local IO abdominal muscle
activity was increased on both sides during bridging exercises and ipsilaterally during fourpoint kneeling exercises, abdominal muscle activity can be changed after a lumbar
stabilization training program in healthy subjects.
In contrast, no significant change in relative muscle activity of the local back muscle MF
was found after training. One reason for this finding is that it may be more difficult to
produce an isolated contraction of the MF during training. This idea is supported by the
clinical experience that, in general, subjects find it easier to concentrate on drawing in the
lower abdomen than on focusing on the lower back muscle contraction. Also, perhaps it
was not possible to train both the deep and the superficial fibres of the MF during the
intervention period. Moseley et al. (2002, 2003, 2004) demonstrated a different activation
of the deep and superficial fibres of the MF anticipating different loading conditions in
standing. Since it has been shown that recording the muscle activity of the deep fibres of
the MF by surface electrodes may be difficult (Stokes et al., 2003), this technique may not
have been sufficiently accurate to detect any changes in activity of the deep MF fibres.
Whatever the reason, the training strategy used in the present study was unable to influence
the muscle activation patterns of the local back muscle.
4.1.2. Global muscle activity
Not only did the local (so-called segmental-stabilizing abdominal) muscle activity levels
change, but also the relative activity of some global (so-called torque-producing and
70
Influence of specific training on trunk muscle recruitment during stabilization exercises
general-stabilizing) muscles changed. After training, the activity of the RA was significantly
higher during the symmetric bridging exercises.
Co-contraction with other abdominal muscles is often reported when subjects are trying to
contract the TA (Richardson et al., 1999). Beith et al. (2001) concluded that while
performing an abdominal hollowing manoeuvre, because elimination of activity in the EO
muscles may be too difficult or even impossible for some to achieve, it may not always be a
feasible goal. Studies on the effect of an isometric contraction of all the abdominal wall
muscles (known as an abdominal brace manoeuvre) showed a considerably higher relative
muscle activity of the RA in exercises 1, 3, 4 and 5 (Kavcic et al., 2004b). However, the
results of the local and global relative muscle activity changes in the present study are
limited to only those subjects who have been shown able to isolate TA contraction
(investigated using real-time ultrasound).
The absence of co-contraction of the more global abdominal muscles during the exercises
in four-point kneeling compared with the bridging exercises, might be explained by the
difference in posture and level of difficulty between the two groups of exercises. The fourpoint kneeling position provides increased awareness of the abdominal wall due to the
gravitational stretch on the muscles, and allows complete relaxation of the abdominal wall.
This position may increase the sensitivity of the stretch receptors and might enhance the
stimulus to contract abdominal muscles separately (Richardson and Jull, 1995; Richardson
et al., 1999; Beith et al., 2001). This stretch of the abdominal wall does not exist in the
supine position, which might make it harder to recruit the deep abdominals separately in
this position.
71
Chapter 3
Table 2
Mean values, standard deviations (SD) and P-values of the ratio local muscle activity/global muscle activity
(mean) during the different exercises
Exercise
SD
1
Post
Mean
SD
1.76
0.91
0.50
7.62
2.93
1.81
6.23
2.18
1.12
Pre
Mean
SD
3
Post
Mean
SD
Ipsilateral
IO/RA
IO/EO
MF/ICLT
8.26
2.70
1.00
3.40
1.96
0.36
9.90
3.35
1.48
6.28
1.95
0.78
Contralateral
IO/RA
IO/EO
MF/ICLT
3.34
0.77
1.48
1.86
0.38
0.79
4.37
1.53
2.48
2.91
1.22
1.92
Pre
Mean
SD
5
Post
Mean
SD
Ipsilateral
IO/RA
IO/EO
MF/ICLT
3.42
0.30
1.63
3.35
0.22
1.05
5.27
0.67
2.58
3.49
0.50
1.50
Contralateral
IO/RA
IO/EO
MF/ICLT
10.13
1.65
0.89
6.47
1.33
0.65
11.89
2.43
0.92
9.77
1.75
1.38
IO/RA
IO/EO
MF/ICLT
Pre
Mean
3.31
1.19
1.21
Exercise
Exercise
SD
2
Post
Mean
SD
2.19
0.54
0.56
7.38
2.34
1.59
5.93
1.85
0.97
Pre
Mean
SD
4
Post
Mean
SD
0.20
0.02*
0.15
4.04
0.43
2.09
3.03
0.32
1.36
5.88
0.95
3.21
4.65
0.61
2.25
0.04*
< 0.001*
0.02*
0.01*
0.01*
0.31
10.02
1.83
0.86
5.07
1.50
0.39
10.77
2.43
1.25
9.66
1.72
1.99
0.72
0.11
0.32
P
Pre
Mean
SD
6
Post
Mean
SD
0.02*
< 0.001*
0.004*
3.36
0.40
1.11
2.84
0.25
0.37
4.99
0.88
1.64
3.83
0.68
1.05
0.05*
0.001*
0.01*
0.44
0.04*
0.91
8.08
1.57
1.01
5.65
1.09
0.28
8.23
2.17
1.27
6.36
1.70
1.21
0.92
0.06
0.31
P
0.001*
< 0.001*
0.01*
P
Pre
Mean
3.19
0.80
1.27
P
0.001*
< 0.001*
0.09
P
P
IO, internal oblique; MF, lumbar multifidus; RA, rectus abdominis; EO, external oblique; ICLT, iliocostalis
lumborum pars thoracis.
* P-value significant at α = 0.05 level
72
Influence of specific training on trunk muscle recruitment during stabilization exercises
4.2. Changes in ratios
In general, analysis of the relative muscle activity levels showed significant changes only in
the local IO after stabilization training. However, analysis of the local to global muscle
activity ratios revealed that all ratios increased after training. This shows that muscle
activity patterns can be changed in a healthy population if stabilization training is
performed with specific attention paid to the so-called local muscles (Richardson et al.,
1999; O’Sullivan, 2000).
The ratio between the local and global muscle activity increased due to a greater increase in
local muscle activity compared with global muscle activity. This increase in the local/global
ratio was significant in most of the bridging exercises. In the four-point kneeling exercises,
the local muscles at the side of the extended leg seemed to be activated to higher intensities
than the global muscles. The increase in activity was also apparent at the contralateral side,
but the difference between the ratios was not significant.
Similar stabilization training in symptomatic chronic LBP patients with clinical evidence of
spondylolysis or spondylolisthesis also resulted in a significant increase in the IO/RA ratio
during an abdominal drawing in manoeuvre (O’Sullivan et al., 1998). Simulations based on
MVIC contractions in several directions predicted that an increase of the IO/RA ratio
would be effective in increasing spinal stability (Van Dieën et al., 2003).
In the present study, the relative muscle activity ratios increased during all exercises
independent of the type of exercise or the surface on which the exercise were performed.
Marshall and Murphy (2005) also demonstrated no change in the IO/RA ratio between
stabilization exercises performed on and off a swiss ball.
A limitation of the present study is that only static phases of stabilization exercises were
evaluated. However, during the intervention period, the exercises were progressed to nonneutral positions (Akuthota et al., 2004) and to dynamic functional movements with upper
and lower extremity movements (Richardson et al., 2004). In addition to the evaluation of
the static phases, further studies could also investigate the more advanced dynamic
movements. The results of our relatively young group of participants may not be
representative for the whole population. However, the present study was primarily
designed to evaluate the effects of a basic stabilization package that could be used in a
prevention program.
73
Chapter 3
5. CONCLUSION
In the present study, healthy subjects learned isolated local muscle contractions (controlled
by ultrasound) and their integration into basic static stabilization exercises. After training,
analysis of the relative muscle activity levels showed a higher activity of the local abdominal
muscles, but not of the local back muscles; minimal changes in global muscle activity also
occurred. Analysis of the local/global relative muscle activity ratios revealed higher ratios
during all exercises after training, although not all differences were significant. This
indicates that muscle recruitment patterns can be changed in healthy subjects after a
training programme that focuses on neuromuscular control, which could be useful in
prevention programs. More studies are needed to substantiate these results.
Acknowledgements
The authors thank Ms. Evelien De Burck and Ms. Wendy Van Loo for their assistance with
collection of the data, Prof. van Maele for statistical advice, and Ms. Iris Wojtowicz for
linguistic corrections.
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77
78
PART II: MUSCLE ACTIVITY DURING
EXERCISES ON SPECIFIC TRAINING DEVICES
79
80
CHAPTER 4
THE RELEVANCE OF INCREASING RESISTANCE ON TRUNK
MUSCLE ACTIVITY DURING SEATED AXIAL ROTATION
Veerle Stevens1, Erik Witvrouw1, Guy Vanderstraeten1,2, Thierry Parlevliet2, Katie
Bouche1,2, Nele Mahieu1, Lieven Danneels1
1
Department of Rehabilitation Sciences and Physiotherapy; Faculty of Medicine and
Health Sciences, Ghent University, Ghent, Belgium.
2
Department of Physical Medicine and Orthopaedic Surgery, Faculty of Medicine and
Health Sciences, Ghent University, Ghent, Belgium.
Physical Therapy in Sport 2007;8(1):7-13
81
Chapter 4
ABSTRACT
Objectives To investigate the electromyographic (EMG) trunk muscle activity during a
low-load instrumented axial rotation exercise (Tergumed) and the relevance of increasing
resistance.
Setting Evaluation was done in a training centre in a university hospital.
Participants Thirty healthy subjects without musculoskeletal or neuromuscular
complaints.
Main Outcome Measures The normalized (as a percentage of maximal voluntary
isometric contractions (MVIC)) EMG activity of 14 abdominal and back muscles were
investigated during dynamic trunk rotation exertions at 30, 50 and 70% of maximum mean
force (MMF).
Results During the low-load (30% MMF) rotation exercise, the internal abdominal oblique
muscle reached activity levels of 30% of MVIC. All the examined back muscles and the
external abdominal obliques reached activity levels of 60% of MVIC.
Increasing the resistance during seated axial rotation, created significantly higher relative
muscle activity levels for all trunk muscles.
Conclusions The results of the present study indicate that increasing resistance to 50%
and 70% MMF during seated axial rotation in a Tergumed training device consistently
created higher relative activity levels in all trunk muscles. In the vulnerable spine
undergoing rehabilitation the results suggest that training at 30% MMF may be sufficient.
KEY WORDS
Electromyography – Rotation – Resistance
82
Trunk muscle activity during seated axial rotation
1. INTRODUCTION
The majority of our everyday activities such as walking, running and most industrial
occupations, require axial rotation of the spine. In most sport activities such as tennis,
racquetball, squash, ice hockey, soccer, rugby, cricket, volleyball, badminton, golf, baseball
and many others, axial rotation is imperative (Evans, Refshauge, Adams, & Aliprandi, 2005;
Kumar, 2004). Rotation of the trunk during tennis serve and groundstroke for example is
an essential part of the development of power and transfer of energy up the kinetic chain
from the lower to upper extremities (Ellenbecker & Roetert, 2004). General agreement
consists on the need to train the athlete in the sportspecific movements.
However, trunk rotation has been reported to be significantly associated with low back
pain (Kumar, 2004). Disc-related lower back injuries are very common in elite athletes
(Gerbino, & d’Hemecourt, 2002; Hickey, Fricker, & McDonald, 1997a & 1997b; Sward,
Hellstrom, Jacobsson, Nyman, & Peterson, 1991). To prevent rotational injuries during
sports and daily activities, coordination and strength training of the muscles which are
important during rotation gains interests. High muscle activity in the erector spinae and
abdominal obliques throughout the baseball batting swing suggested the importance of
emphasizing abdominal and back exercises in a comprehensive exercise and conditioning
program for baseball batters (Shaffer, Jobe, Pink, & Perry, 1993). Activity levels of
approximately 30% of maximal voluntary isometric contraction (MVIC) are appropriate for
muscle coordination training (Jull, & Richardson, 1994; McGill, 1998; Richardson, Hides,
& Hodges, 2004). In contrast, activity levels of at least 60% of MVIC are generally
accepted for basic strength training purposes (Andersson, Ma, & Thorstensson, 1998).
Today, it is of major importance to start retraining of the muscles as fast as possible in
athletes, without risking too much load and high stress on the spine. However, no clear
indication of resistance in rotation exercises has yet been available. Therefore, the main
purpose of the present study was to investigate trunk muscle activation during seated
rotation at low intensity (30% MMF). The second purpose of this study was to evaluate the
clinical relevance of increasing resistance during this exercise.
83
Chapter 4
2. METHODS
2.1. Subjects
Thirty healthy subjects were included in this study. Their mean age was 20.52 (SD 1.74)
years, mean height was 172.69 (SD 8.66) cm and mean weight was 64.34 (SD 10.02) kg.
Subjects were excluded if they reported any past or current low back pain (LBP). Subjects
familiar with coordination or specific trunk training programs were also excluded. All
subjects were informed of the experimental protocol and gave written consent.
Appropriate ethical approval by the Ghent University Ethics Committee had been granted
prior to the commencement of the study.
2.2. Equipment
A rotation device of the Tergumed® Line for the back (Proxomed®, Germany) was used.
The Tergumed system is a fixed weight resistance system which measures range of motion
(by a cable barrel with greased disc and optical encoder) and force (by a strain gauge) in real
time (sample rate of 50 Hz). The interobserver reliability of the equipment was
demonstrated to be excellent (ICC 0.95 – 0.96) for the measurement of the maximal
isometric strength and good (ICC 0.81 – 0.86) for the measurement of the range of motion
(ROM) of the lumbar spine in healthy subjects (Roussel, Nijs, Truijen, Breugelmans, Claes,
& Stassijns, 2006). A limitation of our study was that the reliability in taking measures in
the present population was not investigated.
The muscle activity was recorded by a 16 channels surface EMG system (MyoSystem
1400, Noraxon USA, Inc., Scotssdale, AZ). The raw surface EMG signals were measured at
a bandwidth of 10 - 500 Hz, using a differential amplifier (MyoSystem 2.10, Noraxon Inc,
Scottsdale, AZ). The overall gain was 1000 and the common mode rate rejection ratio was
115 dB. The signals were analogue/digitally (A/D) (12-bit resolution) converted at 1000
Hz and stored in a personal computer.
2.3. Electrodes
Disposable Ag/AgCl surface electrodes (Blue Sensor, Medicotest GmbH, Germany) were
attached parallel to the muscle-fibre orientation, bilaterally over the following abdominal
muscles: the inferior fibres of the internal oblique (IO) (midway between the anterior iliac
spine and symphysis pubis, above the inguinal ligament) (Danneels, Vanderstraeten,
84
Trunk muscle activity during seated axial rotation
Cambier, Witvrouw, Stevens, & De Cuyper, 2001; van Dieën, Cholewicki, & Radebold,
2003; Vera-Garcia, Grenier, & McGill, 2000), the external oblique (EO) (15 cm lateral to
the umbilicus) (Danneels et al., 2001; van Dieën et al., 2003; Vera-Garcia et al., 2000) and
the rectus abdominis (RA) (3 cm lateral to the umbilicus) (Arokoski, Valta, Kankaanpää, &
Airaksinen, 2004; Danneels et al., 2001; van Dieën et al., 2003). The selected back muscles
were: the lumbar multifidus (MF) (lateral to the midline of the body, above and below a
line connecting both posterior superior iliac spines) (Danneels et al., 2002; Macintosh &
Bogduk, 1987), the thoracic part of the iliocostalis lumborum (ICLT) (above and below the
L1 level, midway between the midline and the lateral aspect of the body) (Danneels et al.,
2001; Danneels et al., 2002; Macintosh & Bogduk, 1987), the thoracic part of the
longissimus (LT) (above and below the L1 level, midway between the vertical line through
the posterior superior iliac spine and the midline of the body) (Macintosh & Bogduk,
1987), and the latissimus dorsi (LD) (3 cm lateral and inferior to the inferior angle of the
scapula) (Danneels et al., 2001). The maximal interelectrode spacing between the recording
electrodes was 2.5 cm as recommended by Ng, Kippers, and Richardson (1998), and each
electrode had a pick-up area of approximately 1.0 cm². The skin was prepared by shaving
excess hair and rubbing the skin with alcohol to reduce impedance (typically ≤ 10 kΩ).
2.4. Experimental procedure
The subject was positioned sitting in the rotation Tergumed device, and all restraining
mechanisms and lever arm attachments were adjusted to the subject’s body dimensions, in
accordance with the manufacturers’ instructions. The torso was fixed by a chest restraint
and a thoracic pad. Lateral and posterior pelvic pads and thigh pads secured the position of
the lower limbs and pelvis (Fig. 1).
First, the range of motion was determined. The subject was asked to axially rotate to the
end of the range of rotation and return to the neutral position. In a smooth and continuous
way, without stopping anywhere in between the movement, this was performed three
times. Secondly, three MVICs were performed in the neutral position. The subjects were
asked to perform the maximal contraction within the first two seconds and maintain their
contraction at that level for another three seconds before terminating the trial (Kumar,
Narayan, & Garand, 2002a). Visual feedback, presenting the force signal, and verbal
encouragement were given in an attempt to achieve maximal effort. These exercises were
85
Chapter 4
performed three times with a pause of 15 s in between. The range of motion and maximal
effort tests were followed by a pause of 15 min (Clark, Manini, Mayer, Ploutz-Snyder, &
Graves, 2002; Ng, Parnianpour, Kippers, & Richardson, 2003; Ng, Parnianpour,
Richardson, & Kippers, 2001; Ng, Richardson, Parnianpour, & Kippers, 2002).
Thirdly, submaximal dynamic rotations were performed. To determine the resistance, the
mean maximal force (MMF) obtained during the maximal isometric rotation contractions
was used. Submaximal exercises at 30, 50 and 70% MMF were performed. The exercise
cycles at the different percentages of MMF were performed by each subject at random
order. The cycles consisted of a movement phase away from the neutral midline position
and a phase towards the neutral midline position. Five repetitions of 5 s were performed.
Visual feedback presented as a sinusoidal curve on a notebook, indicating time and ROM,
supported the controlled performance of the exercises. The subject was only allowed to
deviate 5 % of the curve presented. A ROM of 80% of the total ROM was used during
these dynamic exercises.
Each subject attended a familiarization and a testing session. The familiarization session
was included to allow the subject to gain some knowledge of the equipment and testing
procedure (without placement of surface electrodes) (Ng et al., 2002). This session was
held at 3 to 7 days before the testing session.
Fig. 1. Left rotation exercise
86
Trunk muscle activity during seated axial rotation
2.5. Data analysis
Recent research on the Tergumed devices showed that it is more optimal to use the mean
of different trials than to use the value of a single trial (Roussel et al., 2006). The mean of
the three ROM values was calculated by the software BioMC for Sequential Training
Version 1.0.0 (1999-2002 by BfMC GmbH, Leipzig, Denmark). This software also
determined the mean force during the three MVIC trials. During these MVIC trials, the
time point of maximal effort, as indicated on the Tergumed display, was concurrently
marked in the EMG spectrum. The stored EMG data were full-wave rectified and
smoothed (window: 150 ms). Root mean square values (RMS) were calculated to quantify
the amplitude of the EMG signals. All analyzed EMG periods were 2500 ms. The mean
RMS of the three MVIC trials for each muscle was used to provide a basis for EMG signal
amplitude normalization of the data of the submaximal exercises. During the submaximal
exercises, markers were placed between the two movement phases. The mean RMS values
of the 5 movement phases away from the neutral midline position and the 5 movement
phases towards the neutral midline position were calculated. Noraxon MyoResearch
software 2.10 was used for these analyses.
2.6. Statistical analysis
Statistical analysis was performed using SPSS 11.0 software package (SPSS Inc., Chicago,
IL) for Windows. Since no significant differences were present between the right relative
muscle activity during trunk rotation to the right and the left relative muscle activity during
trunk rotation to the left, the term ipsilateral was introduced. Similarly, the contralateral
relative muscle activity was described.
Descriptive statistics were performed of the relative muscle activity levels. An analysis of
variance (ANOVA) for repeated measures was used to analyse the main effects of the four
factors (resistance level, muscle, side and phase) of the relative muscle activity between the
different experimental exercises. The fourfold interaction was not significant. The threefold
interactions ‘resistance*muscle*phase’, ‘resistance*muscle*side’ and ‘muscle*side*phase’
were significant. Consequently, Least Significant Difference (LSD) post hoc tests with
Bonferroni adjustments were performed. The level for statistical significance was set at
0.05. The observed power was 1.00.
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Chapter 4
3. RESULTS
The MMF of the left and right trunk rotation was 593.04 N (SD 159.70) and 585.03 N (SD
148.50) respectively. The work attained during the dynamic submaximal exercises is
presented in Table 1. The mean range of motion of the left and right rotation was,
respectively, 61.29° (SD 5.32) and 62.89° (SD 5.14).
Table 1
Work (Nm) during the different submaximal axial rotation exercises
30% MMF
50% MMF
70% MMF
Left rotation
222.76 (89.20)
345.86 (132.68)
401.03 (191.43)
Right rotation
227.59 (82.31)
324.62 (135.94)
370.00 (171.65)
The normalized EMG activity levels during the dynamic exercises are presented in Figs. 2
and 3.
The results of the rotation at the lowest intensity (30% MMF) demonstrate that the
ipsilateral IO, EO and MF and the contralateral LT showed activity levels between 30%
and 60% of MVIC during the movement phase away from the neutral midline position of
this low-load exercise. During the movement phase towards the neutral midline position,
all ipsilateral back muscles (MF, LT, ICLT and LD) and the contralateral MF demonstrated
activity levels between 30% and 60% of MVIC.
The ipsilateral LT, ICLT and LD and the contralateral EO and MF even reached activity
levels of more than 60% of MVIC during the movement phase away from the neutral
midline position of this 30% MMF exercise.
Both ipsilateral and contralateral RA and the contralateral IO, ICLT and LD showed
activity of less than 30% MVIC during the movement phase away from the neutral midline
position at the lowest intensity (30% MMF). During the movement phase towards the
neutral midline position of this exercise all abdominal muscles and the contralateral LT,
ICLT and LD did not reach activity levels of 30% of MVIC.
The second purpose of this study was to evaluate the clinical relevance of increasing
resistance on the normalized EMG activity. These results showed that increasing resistance
created systematic higher relative muscle activity levels in all trunk muscles. Only the MF
88
Trunk muscle activity during seated axial rotation
showed no significant difference between the activity during the 50% and the 70% MMF
exercise concerning the movement phase away from the neutral midline position.
150
30% MMF
50% MMF
70% MMF
Relative muscle activity (%MVIC)
120
90
60
30
0
IO -I
RA-I
EO -I
MF-I
LT-I
ICLT-I
LD-I
IO -C
RA-C
EO -C
MF-C
LT-C
ICLT-C
LD-C
Muscle
Fig. 2. Relative muscle activity (% MVIC) levels during the phase away from the neutral midline position.
MMF = maximal mean force; I = ipsilateral; C = contralateral; IO = internal oblique; RA = rectus
abdominis; EO = external oblique; MF = lumbar multifidus; LT = longissimus thoracis; ICLT = iliocostalis
lumborum pars thoracis; LD = latissimus dorsi.
150
30% MMF
50% MMF
70% MMF
Relative muscle activity (%MVIC)
120
90
60
30
0
IO -I
RA-I
EO -I
MF-I
LT-I
ICLT-I
LD-I
IO -C
RA-C
EO -C
MF-C
LT-C
ICLT-C
LD-C
Muscle
Fig. 3. Relative muscle activity (% MVIC) levels during the phase towards the neutral midline position. MMF
= maximal mean force; I = ipsilateral; C = contralateral; IO = internal oblique; RA = rectus abdominis; EO
= external oblique; MF = lumbar multifidus; LT = longissimus thoracis; ICLT = iliocostalis lumborum pars
thoracis; LD = latissimus dorsi.
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Chapter 4
4. DISCUSSION
The main purpose of the present study was to investigate if low-load seated rotation
exercises with a resistance of 30% MMF could create sufficient normalized EMG activity
to train the trunk muscles.
Normalized EMG levels of 30% of MVIC have been shown to be appropriate for muscle
coordination purposes (Jull, & Richardson, 1994; McGill, 1998; Richardson et al., 2004).
When training specific movements, not only strength, but also the adequate co-contraction
with the appropriate force and inhibition of different muscles, described as coordination, is
essential to carry out the desired activity (Kottke, 1990).
The results of the present study were described according to the movement phase towards
and away from the neutral midline position. During the phase away from the neutral
midline position, all muscles showed higher activity than during the phase towards the
neutral midline position, except for the RA during the 70% MMF exercise. However,
because the dynamic rotation movement always consists of both phases in clinical practice,
description of the muscle activity levels is clearer when the total movement is considered.
To clarify interpretation of the results of the low-load exercise, a subdivision was made into
the muscles that showed activity of less than 30% of MVIC, between 30% to 60% of
MVIC and finally, more than 60% of MVIC.
Only the RA showed activity levels smaller than 30% of MVIC. Minimal contribution of
the RA to the production of torque in the transverse plane was supposed due to its vertical
alignment (Andersson, Grundström, & Thorstensson, 2002; Ng et al., 2001; Pope,
Andersson, Broman, Svensson, & Zetterberg, 1986).
The IO reached 30% of MVIC, which is appropriate for muscle coordination training. This
activation level could be suggested to be ideal for the IO, because this muscle is often
classified as a local, segmental stabilizing muscle (Bergmark, 1989). However, the division
of trunk muscles into local and global (torque producing) ones mainly results from seeing
the muscles in isolation and not taking into account their intricate functional relationship
with collagenous structures like the fascia. The IO, EO and LD are all strongly related to
the main thoracolumbar fascia (TLF). Muscles like the MF and ICLT have a hydraulic
amplifier effect on the different layers of the TLF (Vleeming, Pool-Goudzwaard, Stoeckart,
van Wingerden, & Snijders, 1995). The posterior layer of the TLF is ideally positioned to
90
Trunk muscle activity during seated axial rotation
regulate tension via its extensive muscular attachments to both “local” and “global”
muscles (Barker, & Briggs, 1999).
The EO and all the back muscles even reached basic strength training levels of more than
60% of MVIC at very low resistances of 30% MMF.
Although the rotation movement in this study, in which the subject was seated with a
neutral lumbar spine position, lacks some functional relevance in relation to most rotation
movements in sports, this seems a safe and useful position which allows early rehabilitation
of injured athletes. At 30% MMF this dynamic rotation exercise is expected to create
minimal tissue load due to the low resistance and the controlled neutral lumbar spine
position (McGill, 2007) in the Tergumed device. Furthermore, disc herniation often related
to rotation movements, appears to be more strongly linked to repeated flexion motion
rather than load (Calaghan & McGill, 2001). Therefore, this low-load rotation exercise
seems safe and creates already strength training of all back muscles and the EO. The
athlete can start early with an efficient training preparing him for specific rotation
movements essential during his sports activities. Low-load exercises are very important
since athletes need to start rehabilitation as fast as possible to maintain their shape and
technique.
However, since LBP patients could demonstrate higher relative muscle activity levels
during these 30% MMF exercises and the present study only investigated healthy subjects,
further research on LBP patients is mandatory.
The second purpose of the current study was to investigate the clinical relevance of
increasing resistance on relative activity of different trunk muscles. Since rotation is very
important in daily living and sport, many researchers have investigated the trunk EMG
activity during rotation movements. However, most studies investigated only isometric
exertions (Bankoff, Moraes, Salve, Lopez, & Ferrarezi, 2000; Moraes & Bankoff, 2003;
Kumar & Narayan, 1998, 1999a & 2001a; Kumar, Zedka, & Narayan, 1999b; Kumar,
Narayan, & Garand, 2001b, 2002a & 2002b; Lavender, Tsuang, & Andersson, 1993;
McGill, 1992; Mirka et al., 1997; Ng et al., 2001, 2002, & 2003; Perez & Nussbaum, 2002;
Swie & Sakamoto, 2004; Torén & Öberg, 1999; Van Dieën, 1996). Despite the common
use of rotation training devices in clinical practice, most research findings are based on
varied rotation positions and complicated settings. Today, the effect of various loads
applied to dynamic rotation movements on trunk muscle activity was not yet reported. To
91
Chapter 4
our knowledge, the present study is the first study which discusses the activity levels during
dynamic low-loaded seated rotation exercises and the relevance of increasing resistance
during these exercises.
The results of the present study indicated that all trunk muscle activity significantly
increased with increasing resistance. However, in general, the IO and RA did not reach
basic strength training levels, even when increasing the resistance to 70% MMF.
Consequently, with regard to the rehabilitation of these muscles it seems of no benefit to
impose higher loads to the spine. It seems possible that this kind of seated axial rotation
exercises is not optimal to train these specific muscle groups. As the rotation movement is
an essential but not unique part of the prevention or rehabilitation training, other
movements such as flexion might provide optimal recruitment of those muscles.
The EO and all back muscles, which reached strength training levels even at low-load
exercises (30% MMF) showed significantly higher relative activity when increasing the
resistance. However, one can argue about the clinical importance of such high muscle
activity training in rehabilitation. To rehabilitate basic strength with minimal injury risk in
the average active population, there seems no need for an increase in resistance during
these rotation exercises since it could create supplementary stress on the lumbar spine and
might be detrimental in the early rehabilitation. However, maximal strength training at
higher relative muscle activity levels as created in the 50% and 70% MMF exercise could be
justified for jobs demanding intensive rotation movements or sportspecific conditions.
5. CONCLUSION
In conclusion, the results of the present study indicate that increasing resistance to 50%
and 70% MMF during seated axial rotation in a Tergumed training device consistently
created higher relative activity levels in all trunk muscles. In the vulnerable spine
undergoing rehabilitation the results suggest that training at 30% MMF may be sufficient.
Acknowledgements
The authors thank Ms. Sofie Haelterman, Ms. Greet Aelbrecht and Mr. Ruben Van Assche
for their assistance with the collection of the data.
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Trunk muscle activity during seated axial rotation
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96
CHAPTER 5
THE EFFECT OF INCREASING RESISTANCE ON TRUNK
MUSCLE ACTIVITY DURING EXTENSION AND FLEXION
EXERCISES ON TRAINING DEVICES
Veerle K. Stevens1, Thierry G. Parlevliet2, Pascal L. Coorevits3, Nele N. Mahieu1,
Katie G. Bouche1, Guy G. Vanderstraeten1, Lieven A. Danneels1
1
Department of Rehabilitation Sciences and Physiotherapy; Faculty of Medicine and
Health Sciences, Ghent University, Ghent, Belgium.
2
Department of Physical Medicine and Orthopaedic Surgery, Faculty of Medicine and
Health Sciences, Ghent University, Ghent, Belgium.
3
Department of Medical Informatics and Statistics, RAMIT vzw, Ghent, Belgium
Journal of Electromyography and Kinesiology, In Press
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Chapter 5
ABSTRACT
Although progressive resistance training of trunk muscles on devices is very common,
today, the effects of increasing resistance on trunk muscle activity during dynamic
extension and flexion movements on training devices have not been reported yet. Thirty
healthy subjects participated in maximal isometric and submaximal dynamic (at 30%, 50%
and 70% of maximum mean torque (MMT)) extension and flexion exercises on Tergumed
lumbar training devices. The normalized (as a percentage of maximal voluntary isometric
contractions (MVIC)) electromyographic activity of 16 abdominal and back muscles was
investigated. The results of the present study indicated that in general, with increasing
resistance from 30% MMT to 50% MMT and 70% MMT, the activity of all back muscles
during the extension exercises and the activity of all abdominal muscles during the flexion
exercises increased significantly. To train strength (>60% of MVIC), low intensities (30%
and 50% MMT) appeared sufficient to affect the back muscles, but for the abdominals
higher resistance (70% MMT) was required. In contrast to the other back muscles, the
lumbar multifidus demonstrated high activity levels during both the extension and the
flexion exercises. As the lumbar multifidus is demonstrated to be an important muscle in
segmental stabilization of the lumbar spine, this finding may help in understanding the
efficacy of rehabilitation programs using specific training devices.
KEY WORDS
Electromyography – Flexion – Extension – Trunk muscle activity
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Trunk muscle activity during extension and flexion exercises on devices
1. INTRODUCTION
Progressive resistance training of the trunk muscles on devices is a common treatment for
low back pain (LBP) (San Juan et al., 2005). Research has shown that muscle
reconditioning on specific devices is not only effective in reducing pain and selfexperienced disability (Kankaanpää et al., 1999; Risch et al., 1993; Taimela et al., 2000), but
it can also modify important psychological factors (Mannion et al., 2001a; Risch et al., 1993;
Taimela et al., 2000), diminish the use of health care services (Leggett et al., 1999) and
increase isometric strength (Mannion et al., 2001b; Risch et al., 1993; Taimela et al., 2000)
and fatigability of the lumbar muscles (Mannion et al., 2001b).
To optimize rehabilitation programs, muscle activation strategies during the performance
of exercises on devices need to be understood. The findings of trunk electromyographic
(EMG) amplitudes during the flexion and extension movements used daily in standing
positions have been reported in a healthy population (Bankoff et al., 2000; Dickey et al.,
2003; Gupta, 2001; Kaigle et al., 1998; Kuriyama and Ito, 2005; Larivière et al., 2000;
Leinonen et al., 2000; Mathieu and Fortin, 2000; Marras and Mirka, 1992; Mirka et al.,
1997; Neblett et al., 2003; Olson et al., 2004; Olson et al., 2006; Paquet et al., 1994; Shirado
et al., 1995; Takahashi et al., 2006; Wolf et al., 1979). Extensive research was also
performed on muscle fatigability (Kankaanpää et al., 2005; Kankaanpää et al., 1997; Lee et
al., 1996; Roy et al., 1989; Sparto et al., 1999; Van Dieën et al., 2003) and muscle activation
during different lifting movements (Arjmand and Shirazi-Adl, 2005; Bonato et al., 2003;
Cresswell and Thorstensson, 1994; Gagnon et al., 2001; Granata and Marras, 1995; Kingma
et al., 2004; Lee and Lee, 2002; Noe et al., 1992; Potvin et al., 1991; Roy et al., 1998;
Takahashi et al., 2006). In training exercises, muscle function was analysed in a standing
position using loads in the hands (Arjmand and Shirazi-Adl, 2006; Peach et al., 1998) and
resistance from a device (Alexiev, 1994; Allison and Henry, 2001; Gallagher, 1997; Granata
et al., 2005; Lee et al., 2006; Ross et al., 1993; Sparto and Parnianpour, 1998; Thelen et al.,
1994). Today, most training on devices occurs in a seated position, because it is a
comfortable posture which limits compensatory movements. Most studies evaluating
muscle activity during flexion and extension exercises in a seated position investigated
isometric (de Moraes and Bankoff, 2003; Kankaanpää et al., 1998; Parkin et al., 2001; Roy
et al., 2003; Tan et al., 1993) and isokinetic (Grabiner and Kasprisin, 1994; Walsworth,
2004) movements. Analysis of dynamic exercises is needed since more complex loading on
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Chapter 5
the spine is created in comparison with static exercises (Davis and Marras, 2000) and
controlled motions are more related to daily life conditions (Marras and Mirka, 1992).
Athough a few studies investigated muscle activation in healthy subjects during dynamic
unresisted (Bankoff et al., 2000) and resisted (Cholewicki et al., 1997; Kankaanpää et al.,
1997; San Juan et al., 2005; Udermann et al., 1999) flexion and extension movements
performed in sitting, several limitations remain. Cholewicki et al. (Cholewicki et al., 1997)
studied the effect of no weight and 32 kg strapped over the shoulders in a semi-seated
position. San Juan et al. (San Juan et al., 2005) and Udermann et al. (Udermann et al., 1999)
investigated isometric and dynamic movements on a training device (MedX). Though they
reported to analyse an extension movement, this was determined as the movement
returning from a flexion position to the neutral spine position. In sitting, the neutral lumbar
spine position is halfway between full extension and a flat position of the spine (Danneels
et al., 2002). In the present study, based on the principles of biomechanics and clinical
evaluation (Edwards, 1994; Kendall et al., 1993; Vleeming et al., 1993) and in agreement
with different other studies (Kankaanpää et al., 1997; Walsworth, 2004), extending the
spine was defined as the backward movement of the trunk starting from the neutral
posture.
Although currently training devices are very popular in clinical practice, no studies have
reported the effect of increasing resistance on trunk muscle activity during dynamic seated
flexion and extension movements on training devices. Consequently, different resistance
levels were applied in this study.
The first purpose of the present study was to analyse the relative activity levels of several
trunk muscles during flexion and extension movements. The second purpose was to
investigate the effect of increasing resistance during flexion and extension movements on
trunk muscle activity in a healthy population.
2. METHODS
2.1. Subjects
Thirty healthy subjects were included in this study. Their mean age was 20.52 (SD 1.74)
years, mean height was 172.69 (SD 8.66) cm and mean weight was 64.34 (SD 10.02) kg.
Subjects were excluded if they reported any past or current back pain. Subjects familiar
100
Trunk muscle activity during extension and flexion exercises on devices
with coordination or specific trunk training programs were also excluded. All subjects were
informed of the experimental protocol and gave written consent. Appropriate ethical
approval by the Ghent University Ethics Committee had been granted prior to the
commencement of the study.
2.2. Equipment
Flexion and extension devices of the Tergumed® Line for the back (Proxomed®, Germany)
were used. The Tergumed system is a fixed weight resistance system which measures range
of motion (ROM) (by a cable barrel with greased disc and optical encoder) and force (by a
strain gauge) in real time (sample rate of 50 Hz). The interobserver reliability of the
equipment was demonstrated to be excellent for the measurement of the maximal
isometric strength and good for the measurement of the ROM of the lumbar spine in
healthy subjects (Roussel et al., 2006).
The muscle activity was recorded by a 16 channels surface EMG system (MyoSystem 1400,
Noraxon USA, Inc., Scotssdale, AZ). The raw surface EMG signals were bandpass-filtered
between 10 and 500 Hz and amplified using a differential amplifier (MyoSystem 2.10,
Noraxon Inc, Scottsdale, AZ). The overall gain was 1000 and the common mode rate
rejection ratio was 115 dB. The signals were analogue/digitally (A/D) (12-bit resolution)
converted at 1000 Hz and stored in a personal computer.
2.3. Electrodes
Disposable Ag/AgCl surface electrodes (Blue Sensor, Medicotest GmbH, Germany) were
attached parallel to the muscle-fibre orientation, bilaterally over the following abdominal
muscles: the inferior fibres of the internal oblique (IO) (midway between the anterior iliac
spine and symphysis pubis, above the inguinal ligament) (Cholewicki et al., 1997; Danneels
et al., 2001; Van Dieën et al., 2003), the external oblique (EO) (15 cm lateral to the
umbilicus) (Cholewicki et al., 1997; Danneels et al., 2001; Peach et al., 1998; Van Dieën et
al., 2003) and the rectus abdominis (RA) (3 cm lateral to the umbilicus) (Cholewicki et al.,
1997; Danneels et al., 2001; Peach et al., 1998; Thelen et al., 1994; Van Dieën et al., 2003).
The selected back muscles were: the lumbar multifidus (MF) (lateral to the midline of the
body, above and below a line connecting both posterior superior iliac spines) (Danneels et
al., 2002; Macintosh and Bogduk, 1987), the lumbar part of the iliocostalis lumborum
(ICLL) (lateral to the vertical line through the posterior superior iliac spine, above the iliac
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Chapter 5
crest) (Macintosh and Bogduk, 1987), the thoracic part of the iliocostalis lumborum (ICLT)
(above and below the L1 level, midway between the midline and the lateral aspect of the
body) (Danneels et al., 2002; Danneels et al., 2001; Macintosh and Bogduk, 1987), the
thoracic part of the longissimus (LT) (above and below the L1 level, midway between the
vertical line through the posterior superior iliac spine and the midline of the body)
(Macintosh and Bogduk, 1987), and the latissimus dorsi (LD) (3 cm lateral and inferior to
the inferior angle of the scapula) (Danneels et al., 2001). The maximal interelectrode
spacing between the recording electrodes was 2.5 cm as recommended by Ng et al. (Ng et
al., 1998), and each electrode had a pick-up area of ≈ 1.0 cm². The skin was prepared by
shaving excess hair and rubbing the skin with alcohol to reduce impedance (typically ≤ 10
kΩ).
2.4. Experimental procedure
The subject was seated in an upright position in the lumbar extension and flexion
Tergumed devices (Figs. 1 and 2). All restraining mechanisms and lever arm attachments
were adjusted to the subject’s body dimensions, in accordance with the manufacturers’
instructions. The knees were flexed at 30° and were positioned so that the thighs were
parallel to the seat (San Juan et al., 2005). The feet were placed on a footboard. A posterior
pelvic pad, a belt and thigh pads secured the position of the lower limbs and pelvis. For the
extension and flexion exercises, force had to be applied to a pad just below the spine of the
scapula and to a pad just below the clavicula respectively. The subjects were asked to cross
the arms and hold the hands on the opposite shoulders.
To obtain similar positions during the different exercises and for subject’s comfort, first all
flexion exercises and secondly all extension exercises were performed or vice versa (at
random).
First, the ROM was determined. The subject was asked to extend or flex the trunk to the
end of extension or flexion and return to the neutral position. In a smooth and continuous
way, without stopping anywhere in between the movement, this was performed three
times. Secondly, three maximal voluntary isometric contractions (MVIC) were performed
in the neutral upright sitting position. The MVIC of the abdominal muscles was obtained
during the isometric flexion exertion and the MVIC of the back muscles during the
isometric extension exertion. The subjects were asked to perform the maximal contraction
102
Trunk muscle activity during extension and flexion exercises on devices
within the first two seconds and maintain their contraction at that level for another three
seconds before terminating the trial (Kumar et al., 2002). Visual feedback, presenting the
force signal, and verbal encouragement were given to enable the subject to give maximal
effort. These exercises were performed three times with a pause of 15 seconds in between.
The ROM and maximal effort tests were followed by a pause of 15 minutes (Clark et al.,
2002; Ng et al., 2003; San Juan et al., 2005).
Thirdly, submaximal dynamic flexion and extension movements were performed. To
determine the resistance, the mean maximal torque (MMT) obtained during the maximal
isometric contractions was used. Dynamic submaximal exercises at 30, 50 and 70% of the
MMT, recorded in the upright position, were performed. The exercise cycles at the
different percentages of MMT were performed by each subject at random order. The cycles
consisted of a movement phase away from the neutral position (extension and flexion) and
a phase towards the neutral position (returning to the neutral position). Five repetitions of
5 seconds were performed. Visual feedback presented as a sinusoidal curve on a notebook,
indicating time and ROM, supported the controlled performance of the exercises. The
subject was only allowed to deviate 5 % of the curve presented. A ROM of 80% of the
total ROM was used during these dynamic exercises.
Each subject attended a familiarization and a testing session. The familiarization session
was included to allow the subject to gain some knowledge of the equipment and testing
procedure (without placement of surface electrodes) (Ng et al., 2002). This session was
held at 3 to 7 days before the testing session.
Fig. 1. Extension movement.
Fig. 2. Flexion movement.
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Chapter 5
2.5. Data analysis
Recent research on the Tergumed devices showed that it is more optimal to use the mean
of different trials than to use the value of a single trial (Roussel et al., 2006). The mean of
the three ROM values was calculated by the software BioMC for Sequential Training
Version 1.0.0 (1999-2002 by BfMC GmbH, Leipzig, Denmark). This software also
determined the mean torque during the three MVIC trials.
The stored EMG data were full-wave rectified and smoothed (window: 150 ms). Root
mean square values (RMS) were calculated to quantify the amplitude of the EMG signals.
All analyzed EMG periods were 2500 ms. The mean RMS of the three MVIC trials for
each muscle was used to provide a basis for EMG signal amplitude normalization of the
data of the submaximal exercises. During the submaximal exercises, markers were placed
between the two movement phases. The mean RMS values of the 5 movement phases
away from the neutral position and the 5 movement phases towards the neutral position
were calculated. Noraxon MyoResearch software 2.10 was used for these analyzes.
2.6. Statistical analysis
Statistical analysis was performed using SPSS 12.0 software package (SPSS Inc., Chicago,
IL) for Windows. The level for statistical significance was set at 0.05.
Descriptive statistics were performed of the relative muscle activity levels.
The dependent variable was EMG. To assess the effects of the four independent variables
(resistance level, muscle, side and phase) on the dependent variable EMG, an analysis of
variance (ANOVA) for repeated measures was performed, separately for flexion and
extension.
Analysis of the extension movement showed a significant 4-way interaction resistance level
x muscle x side x phase (p = 0.01). Consequently, Least Significant Difference (LSD) post
hoc tests with Bonferroni adjustments were performed.
Analysis of the flexion movement demonstrated that the 4-way interaction was not
significant (p = 0.41). The 3-way interactions resistance level x muscle x side (p = 0.52),
resistance level x phase x side (p = 0.84) and phase x muscle x side (p = 0.48) were not
significant. The interaction resistance level x muscle x phase showed a significant p-value (p
< 0.001). The 2-way interaction muscle x side was also significant (p = 0.001).
Consequently, Least Significant Difference (LSD) post hoc tests with Bonferroni
adjustments were performed.
104
Trunk muscle activity during extension and flexion exercises on devices
3. RESULTS
The MMT during extension and flexion was 342.16 Nm (SD 141.96) and 169.96 Nm (SD
63.72) respectively. The mean ROM of the extension and flexion was 25.42 (SD 3.57) and
29.57 (SD 3.76) cm respectively. The normalized EMG activity levels during the dynamic
exercises are presented in Table 1.
The results of the extension movement demonstrated relative MF and LT activity levels of
higher than 60% of MVIC and relative ICLL and ICLT activity levels between 30% and
60% of MVIC during extension at the lowest intensity (30% MMT). Even when returning
to the neutral position during this exercise, all these back muscles showed activity levels of
about 30% of MVIC. The left LD approximated the level of 30% of MVIC during the 70%
MMT exercises. The abdominal muscles presented low relative activity levels during all
extension exercises (5.44 to 18.78 % of MVIC).
Post-hoc tests (the 4-way interaction resistance level x muscle x side x phase was
significant) analysing the effect of the resistance level showed the following results.
Increasing resistance during extension created significant higher relative activity levels in all
back muscles during both movement phases (Figs. 3 and 4). There was no significant
difference between the resistance levels for the activity of the MF during the returning
movement to the neutral position. Concerning the relative abdominal muscle activity,
increasing the resistance during extension did not create significant differences in relative
muscle activity of the IO and RA, but in general, significant increases in relative EO
activity were reported.
Post-hoc tests investigating the effect of the movement phase demonstrated that the
relative activity of all back muscles and the EO was significantly higher during the
movement phase away from the neutral position compared with the phase towards the
neutral position. The relative muscle activity of the IO and RA was not significantly
different between both phases during the 30% MMT and the 50% MMT exercises.
Post-hoc tests analysing the effect of the factor side showed no significant differences in
relative activity between both sides, except for the RA, EO and LD. During all extension
exercises and phases the relative activity of the EO and LD was significantly higher at the
left side compared with the right side and the relative activity of the RA was significantly
higher at the right side compared with the left side. During the movement phase towards
105
Chapter 5
the neutral position, the left MF also showed significantly higher relative activity than the
right MF.
The results of the flexion movement demonstrated that no single muscle exceeded the 25% of
MVIC activity level during the low-intensity exercise (30% MMT). The abdominal muscles
reached activity levels of about 30% of MVIC and 60% of MVIC during flexion at 50%
MMT and 70% MMT respectively. In contrast to the other back muscles that showed low
activity levels during all flexion movements (5.68 to 16.85 % of MVIC), the MF showed
relative activity of more than 30% of MVIC during flexion at the 70% level.
Post-hoc tests (the 3-way interaction resistance level x muscle x phase was significant)
analysing the effect of the resistance level showed the following results. Increasing
resistance during the flexion movements created significant higher relative activity levels in
all abdominal muscles (Figs. 5 and 6). In general, back muscle activity was not significantly
different between 30% and 50% MMT (except for the ICLL and ICLT during flexion), but
increasing resistance to 70% MMT caused significantly higher back muscle activity.
Post-hoc tests investigating the effect of the movement phase demonstrated that the
relative activity of all muscles was significantly higher in the movement phase away from
the neutral position compared to the movement phase towards the neutral position. Only
the MF during the 30% MMT exercise and the LT during the 50% MMT exercise showed
no significant differences between both movement phases.
The 2-way interaction muscle x side was significant (p = 0.001) and post-hoc analysis
showed significant higher relative activity for the RA, ICLL, LT and ICLT at the right side
compared with the left side.
106
Trunk muscle activity during extension and flexion exercises on devices
Table 1
Data on relative EMG activity (% of MVIC) during the extension and flexion exercises (means and standard deviations; SD).
INTERNAL OBLIQUE
Left
RECTUS ABDOMINIS
Right
Left
EXTERNAL OBLIQUE
Right
Left
LUMBAR MULTIFIDUS
Right
Left
ILIOCOST LUMB LUMB
Right
Left
LONGIS THOR
Right
Left
ILIOCOST LUMB THOR
Right
Left
LATISSIMUS DORSI
Right
Left
Right
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Mean
SD
Phase away from neutral
15,22
14,17
13,78
11,74
7,58
5,46
17,34
16,68
7,72
4,53
5,62
4,06
66,94
53,20
66,38
43,81
46,08
24,26
44,84
28,55
64,34
40,08
62,53
41,09
48,26
21,38
45,10
24,97
12,25
6,53
9,29
4,66
Phase towards neutral
15,52
14,34
13,92
11,87
7,15
5,38
17,64
17,08
7,47
4,51
5,44
4,01
54,92
54,97
49,33
37,11
26,39
13,16
27,14
15,04
42,70
23,41
43,88
23,98
33,20
14,36
33,98
16,02
11,36
6,21
8,73
4,62
Phase away from neutral
14,23
12,76
12,81
10,67
8,45
5,17
17,04
16,57
8,57
4,83
5,88
4,50
84,96
55,54
85,79
58,14
69,24
31,32
67,92
41,69
90,88
47,49
80,05
25,85
69,07
27,89
63,86
33,50
18,65
8,75
13,99
6,49
Phase towards neutral
13,78
12,72
12,58
10,97
8,70
8,40
16,63
16,36
7,67
4,52
5,39
4,12
56,06
35,14
55,29
32,89
37,83
17,15
39,95
22,22
56,94
29,52
58,81
33,92
45,36
17,92
44,59
20,69
15,58
7,36
11,61
5,34
Phase away from neutral
15,58
14,15
14,76
12,30
9,83
6,69
18,78
16,40
10,69
7,36
7,32
6,90
113,39
76,80
112,21
71,06
102,02
49,43
107,67
71,21
119,34
65,64
106,54
34,31
92,33
40,41
87,31
43,86
29,72
15,71
25,13
15,67
Phase towards neutral
13,87
13,22
12,92
11,93
8,20
5,89
17,55
16,19
8,30
4,92
5,95
4,63
64,16
39,11
66,84
41,93
50,16
23,43
56,28
34,95
67,36
34,31
71,20
45,88
54,38
21,15
54,95
25,98
21,61
11,21
17,76
9,36
Phase away from neutral
21,12
11,62
21,34
16,40
13,00
9,73
19,78
13,05
15,48
8,15
14,74
7,82
25,20
29,59
24,40
28,66
10,96
8,87
13,72
8,47
10,52
6,70
13,27
8,81
5,69
2,83
10,53
6,40
10,65
6,55
9,24
4,28
Phase towards neutral
13,38
6,22
13,21
6,43
8,44
4,87
14,65
8,22
9,55
4,25
9,06
3,98
22,93
27,41
21,53
26,06
8,97
8,17
11,92
8,21
11,99
8,82
16,29
13,73
6,22
3,80
12,77
8,50
9,66
6,76
8,00
3,66
Phase away from neutral
37,44
15,59
37,94
15,12
27,79
19,49
33,82
22,92
32,53
15,87
29,83
12,86
27,79
23,20
27,32
22,38
13,45
9,21
16,85
8,85
10,61
6,56
12,75
7,51
7,28
4,04
11,20
6,52
10,45
6,55
9,02
4,00
Phase towards neutral
23,05
9,58
22,25
7,76
18,54
13,21
24,46
13,48
20,31
8,75
19,09
7,79
21,05
21,52
20,53
20,11
9,39
8,03
12,13
7,08
10,33
7,45
12,96
9,90
5,68
3,84
10,85
7,28
9,36
6,29
7,67
3,36
EXTENSION
30% MMT EXERCISE
50% MMT EXERCISE
70% MMT EXERCISE
FLEXION
30% MMT EXERCISE
50% MMT EXERCISE
70% MMT EXERCISE
Phase away from neutral
68,14
27,83
69,24
26,34
57,08
36,10
63,29
43,66
64,21
33,24
59,79
26,05
39,76
33,53
41,10
33,04
19,13
11,70
23,01
13,85
12,87
7,86
15,62
8,81
10,50
5,24
13,77
8,20
13,68
8,73
10,93
4,51
Phase towards neutral
39,46
15,17
40,41
11,31
37,07
24,29
42,37
26,62
41,17
18,61
40,38
17,19
28,80
34,06
30,38
34,24
12,23
8,74
14,51
8,27
10,66
6,96
13,36
8,29
6,96
3,51
11,47
7,00
11,14
7,11
8,73
3,41
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Chapter 5
150
30% MMF
50% MMF
70% MMF
Relative EMG activity (% of MVIC)
120
90
60
30
0
IO-L
IO-R
RA-L
RA-R
EO-L
EO-R
MF-L
MF-R ICLL-L ICLL-R LT -L
LT -R ICLT-L ICLT -R LD-L
LD-R
Muscle
Fig. 3. Effect of increasing resistance on the relative muscle activity levels during the extension movement –
phase away from the neutral position (extension).
150
30% MMF
50% MMF
70% MMF
Relative EMG activity (% of MVIC)
120
90
60
30
0
IO-L
IO-R
RA-L
RA-R
EO-L
EO-R
MF-L
MF-R ICLL-L ICLL-R LT -L
LT -R ICLT-L ICLT -R LD-L
LD-R
Muscle
Fig. 4. Effect of increasing resistance on the relative muscle activity levels during the extension movement –
phase towards the neutral position.
108
Trunk muscle activity during extension and flexion exercises on devices
150
30% MMF
50% MMF
70% MMF
Relative EMG activity (% of MVIC)
120
90
60
30
0
IO-L
IO-R
RA-L
RA-R
EO-L
EO-R
MF-L
MF-R ICLL-L ICLL-R LT -L
LT -R ICLT-L ICLT -R LD-L
LD-R
Muscle
Fig. 5. Effect of increasing resistance on the relative muscle activity levels during the flexion movement –
phase away from the neutral position (flexion).
150
30% MMF
50% MMF
70% MMF
Relative EMG activity (% of MVIC)
120
90
60
30
0
IO-L
IO-R
RA-L
RA-R
EO-L
EO-R
MF-L
MF-R ICLL-L ICLL-R LT -L
LT -R ICLT-L ICLT -R LD-L
LD-R
Muscle
Fig. 6. Effect of increasing resistance on the relative muscle activity levels during the flexion movement –
phase towards the neutral position.
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Chapter 5
4. DISCUSSION
The purposes of the present study were to investigate the activity levels and the effect of
increasing resistance during seated extension and flexion exercises on relative muscle
activity of the trunk.
In general, during the extension exercises, the relative back muscle activity was high and
the abdominal muscles showed low relative activity levels. The relative activity of all back
muscles increased significantly with increasing resistance from 30% MMT to 50% MMT
and 70% MMT.
Particularly during the movement phase away from the neutral position, the back muscles
reached high activity levels. At 30% MMT resistance, the MF and LT demonstrated activity
levels of about 60% of MVIC. Activity levels of at least 60% of MVIC are generally
accepted for basic strength training purposes (Andersson et al., 1998). In the 70% MMT
exercise, these relative activity levels were almost doubled. The uncomplicated pelvic
stabilization as commonly used on the Tergumed devices may have contributed to these
high activity levels of the MF (San Juan et al., 2005). Pelvic stabilization was shown to be
necessary for restricting pelvic motion (Petersen et al., 1987), for isolating and strengthen
the lumbar erector spinae muscles (Graves et al., 1994) and to obtain higher activity of the
MF (San Juan et al., 2005) during extension movements on devices. However, debate exists
on the need for pelvic stabilization. Other researchers reported that pelvic stabilization did
not influence muscle forces (Petersen et al., 1987) and activation of gluteus maximus (GM)
and hamstrings (Udermann et al., 1999). Pelvic stabilization was considered not so
important (Walsworth, 2004) or even not needed to strengthen the lumbar erector spinae
muscles (Mayer et al., 2002).
The thoracic and lumbar part of the iliocostalis lumborum reached activity levels between
30 and 60% of MVIC during the low resistance 30% MMT exercise. Relative EMG levels
of 30% of MVIC have been shown to be appropriate for muscle coordination purposes
(Jull and Richardson, 1994; McGill, 1998; Richardson et al., 2004). When training specific
movements, not only strength, but also the adequate co-contraction with the appropriate
force and inhibition of different muscles, described as coordination, is essential to carry out
the desired activity (Kottke, 1990). To train this coordination function and to create
controlled dynamic movements, the Tergumed device in the present study displayed both
110
Trunk muscle activity during extension and flexion exercises on devices
ROM and pacing of the movements. Biofeedback devices were described to serve as an
automated “coach”, cuing the athlete or patient for cadence and effort (Cassisi et al., 1993).
Cholewicki and Van Vliet (Cholewicki and Van Vliet, 2002) reported that the lumbar back
muscles showed the largest contribution to spine stability during isometric extension
exertions, but not during flexion trials.
At 50% MMT resistance, both the thoracic and lumbar part of the iliocostalis lumborum
reached strength training activity levels (60% of MVIC).
During the 70% MMT exercise, the activity levels obtained during the lowest resistance
exercise (30% MMT) were almost doubled. Consequently, the MF, ICLL and ICLT
reached relative activity levels of more than 100% of MVIC during the movement phase
away from the neutral position in the 70% MMT extension exercise. Relative activity levels
exceeding 100% of MVIC suggest inadequate maximal exertions. To ensure that maximum
EMG was obtained, subjects were asked to return the next week to perform manually
resisted maximal exertions (Danneels et al., 2001). In general, no significant differences
were found between the manual resisted and the device resisted maximal EMG. The MVIC
of the RA and ICLL were higher when performed on the devices. Though isometric
exercises are often used to normalize dynamic movements (Cholewicki et al., 1997;
Gallagher, 1997; Udermann et al., 1999; Walsworth, 2004), length-force properties may
have caused high relative activity levels. Analysis of EMG signals over the full ROM may
ignore the differences in EMG-force relationships and this could be regarded as a
limitation of the present study. However, other procedures often fail to maintain the
dynamic character of the exercises.
The results of the present study were described according to the movement phase towards
and away from the neutral position. In general, all muscles showed higher relative activity
during the phase away from the neutral position than during the phase towards the neutral
position. Concerning a flexion movement in standing, Nouwen et al. (Nouwen et al., 1987)
reported similar findings for the abdominal muscles, but opposite results for the paraspinal
muscles. A change in neural drive to the muscles (Gabriel et al., 2006), possibly caused by
the subjects’ thoughts that it is harder to push against a resistance and move away from the
neutral upright sitting position than preventing the resistance from dropping down and
moving towards the neutral position, might have created the higher EMG activity during
the phase away from the neutral position of both flexion and extension exercises.
Nevertheless, because the dynamic flexion and extension movements always consist of
111
Chapter 5
both phases in clinical practice, description of the muscle activity levels is clearer when the
total movement is considered.
Considering the global exercises including both phases, the extension movements in the
present study created an adequate training of the back muscles. In accordance with the
results of isometric seated extension exercises (Tan et al., 1993), greater activation of the
more medially located back muscles (MF and LT) was demonstrated compared with the
more lateral located thoracic and lumbar part of the iliocostalis lumborum.
The relative activity levels of the LD were much lower (< 30% of MVIC, even during the
70% MMT exercise). During extension exercises in standing, the LD also appeared to be
not susceptible to trunk angle changes (Gallagher, 1997). Due to the anatomical
attachments to the humerus, this muscle also has an important role at the shoulder joint.
This shoulder joint was not involved in this movement since the subjects were asked to
cross the arms and hold the hands on the opposite shoulders. The lower activity levels
might also be adequate to stabilize the trunk. The LD in association with the GM can
induce tension in the posterior layer of the thoracolumbar fascia and may contribute to
limitation of joint movement by simultaneously stiffening the muscles and fascia of the
lumbar spine and sacroiliac joint while enabling transfer of loads between trunk and limbs
(Vleeming et al., 1995). In the present study, because the subjects were seated, the activity
of the GM could not be measured accurately.
Although the relative activity levels of the EO also increased significantly with increasing
resistance, the EO never exceeded 11% of MVIC. Both EO and LD showed higher
relative activity levels at the left side compared with the right side. Minimal movement to
left lateral flexion of the upper torso during the extension exercises could have contributed
to the asymmetric activity of these muscles. The location of all weights and the basis of the
device at the left side of the subject may have caused less symmetric activity.
During the extension exercises, in general, the relative activity of the IO and RA did not
differ significantly between the exercises at different resistance levels. Since the activity
levels of those muscles were similar during all resistance levels and during both phases, a
stabilizing function of the IO and RA during the extension movement might be expected.
In accordance with the present findings, external resistance induced no significant activity
of the RA during flexion movements (Takahashi et al., 2006) and movements starting from
various flexion positions to neutral (Ross et al., 1993) in standing. Research on rotation
112
Trunk muscle activity during extension and flexion exercises on devices
exercises demonstrated a global stabilizing role of the lumbar spine for the RA (Ng et al.,
2001). In contrast, during various isometric flexion and extension exertions the RA was
reported to have a negligible effect on spine stability (Cholewicki and Van Vliet, 2002). In
the present study, RA showed significant higher relative activity at the right side in
comparison with the left side. These contradictory findings concerning RA activity might
be attributed to the different neuromuscular requirements for controlling dynamic versus
isometric activities (Ross et al., 1993). The IO, investigated at a location where the direction
of the muscle fibres is similar to those of the transversus abdominis (Marshall and Murphy,
2003; Urquhart et al., 2005), showed no significant differences between both sides and
might demonstrate the commonly accepted segmental stabilizing role of the latter muscle.
Since in vitro experiments with a lumbar spine model demonstrated that activity levels of at
least 1 to 3% MVIC of the MF, ICLL and LT were sufficient to ensure segmental stability
of the lumbar spine (Cholewicki and McGill, 1996), the low activity levels of the IO and
RA are assumed to be adequate. However, this has not yet been evaluated in abdominal
muscles.
In general, during the flexion exercises, the relative abdominal muscle activity was about 30%
of MVIC during the 50% MMT exercise. Except for the MF, the relative back muscle
activity was low during flexion movements. The relative activity of all abdominal muscles
increased significantly with increasing resistance from 30% MMT to 50% MMT and 70%
MMT.
Fifty percent MMT resistance appeared necessary to obtain relative abdominal activity
levels of 30% of MVIC, deemed important for coordination training purposes (Jull and
Richardson, 1994; McGill, 1998; Richardson et al., 2004). Strength training levels of 60% of
MVIC were demonstrated during the 70% MMT exercise. However, the relative abdominal
muscle activity levels during the flexion exercises were lower than the activity levels
obtained by the back muscles during the extension exercises. Antagonistic muscle activity
can indicate co-activity of the trunk musculature system (Davis and Marras, 2000; Lee et al.,
2006) and might be affected more by dynamics than agonistic muscle activity (Davis and
Marras, 2000). It is speculated that muscle co-activity may contribute to trunk stability
(Davis and Marras, 2000; Granata and Marras, 1995; Granata and Marras, 2000).
113
Chapter 5
The RA, the ICLL, LT and ICLT showed higher relative activity at the right side in
comparison with the left side. Since handedness has been shown to influence EMG (De
Luca et al., 1986; Merletti et al., 1994) and all but three subjects were right handed, this
could be involved in the higher relative activity at the right side. In chronic back pain
patients (Larivière et al., 2000; Nouwen et al., 1987) and in healthy subjects (Nouwen et al.,
1987), during flexion and extension exercises from a standing posture, paraspinal EMG
was also demonstrated to be higher on the right side than on the left.
As expected, in general, the relative back muscle activity was low during the flexion
exercises (not higher than 23% of MVIC). According to Tan et al. (Tan et al., 1993), the
erector spinae muscles seem to have a mechanical advantage in trunk flexion which
increases torque production with less EMG output. In contrast to the other back muscles,
the MF demonstrated relative activity levels between 20% and 42% of MVIC during the
flexion exercises and showed no significant differences between the left and right relative
EMG activity. The MF is described as thé muscle important for controlling and stabilizing
the lumbar spine and seemed to be recruited symmetrically and at moderate to high levels
during almost all of these flexion and extension exercises. Inhibition and selected atrophy
of MF has been shown by changes in activation (Cassisi et al., 1993), fatiguability
(Biedermann et al., 1991; Roy et al., 1998), composition (Yoshihara et al., 2001; Zhao et al.,
2000), size and consistency (Danneels et al., 2000; Hides et al., 1994) in LBP patients
compared to healthy controls. Although the present study only investigated young healthy
subjects and further investigation in LBP populations is indispensable, the current findings
concerning the activation of the MF during these flexion and extension exercises are
encouraging.
5. CONCLUSION
The results of the present study indicated that in general, with increasing resistance from
30% MMT to 50% MMT and 70% MMT, the activity of all back muscles during the
extension exercises and the activity of all abdominal muscles during the flexion exercises
increased significantly. The exercises in the present study created adequate coordination
and strength training activity levels of the back and abdominal muscles during extension
114
Trunk muscle activity during extension and flexion exercises on devices
and flexion respectively. Though the flexion and extension movements were symmetric,
several muscles demonstrated asymmetric activity. To train strength, for the MF and LT
low resistance of 30% MMT and for the ICLL and ICLT 50% MMT extension exercises
were sufficient, but for the abdominals higher resistance (70% MMT) was required. In
contrast to the other back muscles, the lumbar multifidus demonstrated high activity levels
during both the extension and flexion exercises. As the MF is demonstrated to be an
important muscle in segmental stabilization of the lumbar spine, this finding might help in
understanding the efficacy of rehabilitation programs using specific training devices.
Acknowledgements
The authors thank Ms. Sofie Haelterman, Ms. Greet Aelbrecht and Mr. Ruben Van Assche
for their assistance with the collection of the data.
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124
PART III: EFFECTIVENESS OF SPECIFIC
EXERCISE THERAPY VERSUS EXERCISE
THERAPY ON DEVICES
125
126
CHAPTER 6
RELIABILITY OF A FUNCTIONAL CLINICAL TEST BATTERY
EVALUATING POSTURAL CONTROL, PROPRIOCEPTION AND
TRUNK MUSCLE ACTIVITY
Veerle K. Stevens, Katie G. Bouche, Nele N. Mahieu, Dirk C. Cambier,
Guy G. Vanderstraeten, Lieven A. Danneels
Department of Rehabilitation Sciences and Physiotherapy, Faculty of Medicine and Health
Sciences, Ghent University, Ghent, Belgium.
American Journal of Physical Medicine and Rehabilitation 2006;85(9):727-736
127
Chapter 6
ABSTRACT
Objective
The purpose of this study was to examine the repeatability and reproducibility of the
different tests of a clinical test battery evaluating the components of functional spinal
stability: i.e. postural control (sway velocity data), proprioception (repositioning error) and
muscle activation (electromyographic data).
Design
A total of 28 healthy volunteers participated in this study: 14 in the repeatability study and
14 in the reproducibility study. Each subject was tested three times with an interval of 1
week between the test sessions. The intraclass correlation coefficients and the standard
error of the measurements as a percentage of the grand mean were calculated.
Results
The intraclass correlation coefficients for both the repeatability and the reproducibility
evaluation showed good to excellent reliability for all variables (ICC 0.60–0.98). The
standard error of the measurements as a percentage of the grand mean ranged from 0.004
to 19.94.
Conclusions
The functional clinical test battery investigated in this study proved to be a reliable tool in
the assessment of healthy subjects. The evaluation of postural control, proprioception and
muscle activity (coordination, stabilization, maximal voluntary isometric contraction,
endurance and flexion-relaxation) showed good to excellent repeatability and
reproducibility. Further analysis of the reliability of these parameters in a clinical setting,
particularly in patients with low back pain, seems appropriate.
KEY WORDS
Repeatability – Reproducibility – Functional stability – Electromyography – Test
battery
128
Reliability of a functional clinical test battery
Lumbar back disorders are very common. A British group recently reported that the
prevalence of low back pain (LBP) is higher than 40 years ago.1 To curtail this high
prevalence and the related socio-economic implications, reliable assessment tools are
needed in clinical practice. In contrast to the one-sided evaluation methods used in the
past, combining multiple tests allows to obtain a global assessment of each individual.
In the present study, different clinical tests were chosen based on the components of
functional stability of the lumbar spine, as determined by: (1) passive structures of the
spine, (2) muscle functional characteristics, (3) neuromuscular control, and (4) postural
control.2 To evaluate the ability to relax the back muscles, a full trunk flexion exercise was
added to the functional clinical test battery.
The purpose of the present study was to examine the repeatability and reproducibility of
the different tests of a clinical test battery evaluating postural control (sway velocity data),
proprioception (repositioning error), and muscle activation (electromyographic [EMG]
data).
METHODS
Subjects
Two groups of healthy, active subjects were included in this study. Oral/written requests
were made to colleagues, family and friends to serve as test subjects. Excluded were
subjects with a history of musculoskeletal/neuromuscular complaints or earlier visits to a
physician for back problems, and subjects who had already experienced back pain that
affected their daily activities. A total of 14 subjects (seven men and seven women)
volunteered for the repeatability study; their mean age was 38.71 (SD 11.75) yrs, mean
height was 171.07 (SD 11.27) cm, and mean weight was 63.29 (SD 9.17) kg. Fourteen other
subjects (eight men and six women) volunteered to participate in the reproducibility study;
their mean age was 39.50 (SD 11.20) yrs, mean height was 170.36 (SD 10.96) cm, and mean
weight was 66.43 (SD 10.29) kg. All subjects were informed of the experimental protocol
and gave written consent. The study was approved by the Ethics Committee of Ghent
University.
129
Chapter 6
Testers
The four testers were physical therapists in the final year of a 2-yr postgraduate course on
manual therapy. Because none of them were familiar with the tests or the equipment before
the start of the present study, all testers practised together. They agreed on a standard
protocol that was used during all test sessions to ensure a strictly standardized performance
of the tests, and to guarantee that each subject was given exactly the same information.
Experimental procedure and equipment
In the repeatability study, the same tester evaluated all 14 subjects three times, with a 1week interval between each test session. In the reproducibility study, all 14 subjects were
tested by three different testers on three different occasions, again with a 1-week interval
between the test sessions. All tests were performed at the same time each day. For the
reproducibility study, the order in which a subject was tested by one of the testers (i.e. first
by tester 1, or 2 or by tester 3) was randomly determined using numbered cards. For
practical reasons and for the subjects’ comfort, the sequence of the exercises was fixed.3
The subjects were allowed to rest between the different exercises to minimize the effects of
fatigue. The endurance tests of the abdominal and back muscles were performed at the end
of each session.
In both studies, the subjects were asked to perform 26 exercises, subdivided into three
categories: postural control, proprioception, and muscle activity. The total time needed to
complete the test protocol was about 1.5 hrs.
Postural control
Postural control was evaluated by a unilateral stance test on a force plate. The bare feet
were placed in a standardized position, and the subject was asked to hold the hands on the
iliac crest. The subject had to perform a unilateral hip flexion, lifting the foot to a height of
10.5 cm while keeping the lower leg in a vertical position. Standing on the left and on the
right foot, and with the eyes open and closed, the subject had to maintain this position for
10 secs (exercises 1 - 4). Each exercise was performed three times, and for every condition
one extra trial was allowed.
A Balance Master dual forceplate (version 8.0, NeuroCom International, Inc., Clackamas,
OR) was used to measure unilateral stance in the balance point position. The forceplate
consisted of two 23 × 152 cm footplates connected by a pin joint. Each footplate rested on
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Reliability of a functional clinical test battery
two force transducers with sensitive axes oriented vertically. The data from the force plate
were stored on a computer until analysis.
Proprioception
Proprioception was determined by measuring the position-reposition accuracy of the
lumbar spine. To define both position and reposition, the coordinates of the spinous
processes of the lumbar spine were obtained using a three-dimensional analysis system. A
pointer held by the tester touched the marked spinous processes. The subject was seated
on a stool with 95 degrees of knee flexion, feet placed at hip width, and arms hanging
freely alongside the trunk (exercise 5). First, the tester placed the subject in a neutral
lumbar spine position. In sitting, the neutral spine position was halfway between full
extension and a flat position of the spine.4 Data on this position were stored. After
performing three pelvic rotations (anterior and posterior pelvic rotation), the subject was
asked to reassume the reference position as accurately as possible. This position-reposition
cycle was repeated three times. The same procedure was repeated in a standing position,
with the feet placed at hip width, and the arms hanging freely alongside the trunk (exercise
6). The neutral spine position in standing was determined by a horizontal alignment
between the anterior superior iliac spine and the posterior superior iliac spine.4
To evaluate the proprioception of the lumbar region, an ultrasound movement analysis
system (Zebris CMS70P, Isny, Germany) was used. The three-dimensional data of the
spinous processes of the lumbar spine were calculated by measuring the travel time of the
ultrasonic pulses by markers on a pointer to three built-in microphones on a tripod. The
data were collected at a sampling rate of 10 Hz.
Muscle activity
Trunk muscle activity was investigated during six categories of exercises: maximal voluntary
isometric contractions (MVICs), coordination, stabilization with limb movements,
stabilization with trunk movements, flexion-relaxation (of the back muscles), and
endurance. Each exercise was explained and demonstrated by the tester, and the subject
was then allowed to practice until proper pacing was achieved. A pace of 60 beats/min was
set by a metronome. Each exercise was performed three times.
Because of the many different muscles, Bergmark5 suggested a classification of trunk
muscles into two groups. Based on anatomical characteristics, Bergmark5 made a
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Chapter 6
distinction between trunk muscles important for segmental stabilization of the vertebrae
(deep local muscles), and muscles used for global stabilization and torque production
(global superficial muscles). Muscles such as the transversus abdominis, the inferior fibres
of the internal oblique and the lumbar multifidus were classified as local muscles. The
global muscle group consisted of many muscles, including the external oblique and the
thoracic part of the iliocostalis lumborum. Therefore, in the current test battery, muscles
from both these groups were selected.
Parallel to the muscle fiber orientation, surface electrodes were attached bilaterally over the
following local trunk muscles: the inferior fibres of the internal oblique6 and the lumbar
multifidus6. The selected global trunk muscles were the external oblique6 and the thoracic
part of the iliocostalis lumborum3,6. The maximal interelectrode spacing between the
recording electrodes was 2.5 cm. The skin was prepared by shaving excess hair and rubbing
the skin with alcohol to reduce impedance (typically ≤ 10 kOhm).
In the repeatability study, use of a personalised template ensured exact replacement of the
electrodes to reduce variability caused by electrode positioning.3
Maximal voluntary isometric contractions
There were three different isometric exercises, which were described previously by
Danneels et al.6 Figure 1 presents photographs of exercises 8 and 9. During all exercises the
tester verbally encouraged the subject to give maximal effort.
Coordination
During the coordination exercises, the trunk muscle activity generated by the subject to
maintain the neutral spine position during a posture was measured. In sitting (exercise 10)
and standing (exercise 11), the tester determined the neutral lumbar spine position, and the
subject was asked to maintain this position for 3 secs before relaxing. The subject was
seated on a stool with 95 degrees of knee flexion, feet at hip width, and arms hanging freely
alongside the trunk. In standing, the feet were at hip width and the arms were relaxed.
Stabilization exercises with limb movements (Type 1)
During the stabilization exercises (types 1 and 2), the trunk muscle activity generated by the
subject to maintain the neutral spine position during limb and trunk movements was
measured. In sitting (exercises 12 - 16) and standing (exercises 17 - 21) movements of arms
132
Reliability of a functional clinical test battery
and legs were added. Figure 2 illustrates exercises 12, 14 and 21. The tester determined the
neutral lumbar spine position. The subject was asked to lift the limb in a standardized and
controlled manner during 3 secs at a uniform speed, hold this position for 3 secs (static
phase) and then return to the original position during 3 secs. The subject was asked to hold
the neutral spine position throughout the exercise.
The movement of the arm consisted of a 90-degree flexion movement of the shoulder with
the elbow extended and a dumbbell of 1.5 kg held in the hand. In both sitting and standing,
the left, right, and both shoulders were flexed. The leg movement was a hip flexion with a
vertical position of the lower leg until the foot was at a height of 10.5 cm in a sitting
position and a height of 25.5 cm when standing. This position was standardized by the
placement of a rope above the knee.
Stabilization exercises with trunk movements (Type 2)
During the stabilization exercises with trunk movements, the subject was asked to perform
a 45-degree controlled and paced trunk flexion while maintaining the neutral spine position
that was determined by the tester. This was performed in a sitting (Fig. 2) and in a standing
position (exercises 22 and 23).
Flexion-relaxation
The flexion-relaxation exercise was designed to evaluate the ability of the back muscles to
relax in a full trunk flexion position. The subject was standing with the feet at hip width
and was asked to bend forward as far as possible (while relaxing the arms and head, but
keeping the knees straight). At the moment the subjects stated they were in a full trunk
flexion position, they were asked to relax all muscles and EMG data were collected for 3
secs (exercise 24).
Endurance
The isometric endurance exercise for the abdominal muscles consisted of an unsupported,
straight-knee sitting position, with the trunk held at a 45-degree angle (exercise 25). To
prevent extreme thoracic flexion, the hands were placed on the shoulders and the arms
were flexed alongside the trunk. Once this position was optimal, a tape was placed at the
fifth thoracic vertebra level, connecting both scapulae, to detect compensation maneuvers.
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Chapter 6
The back muscle isometric endurance test was the modified Biering-Sørensen test (exercise
26). The subjects were placed in a prone position on a bench with the anterior superior iliac
spine at the rotation point of the bench. The legs were strapped to the table with two belts
to prevent them from moving. With the hands under the forehead, the elbows pointing
outwards and a neutral head position, the subject was asked to hold this antigravity
position for as long as possible. Verbal encouragement was given by the tester during both
endurance tests to ensure that the maximal effort was produced by the subject.
Figure 1 presents photographs of these exercises.
The muscle activity was recorded by a surface EMG system with eigth channels
(MyoSystem 1400, Noraxon Inc, Scotsdale, AZ, USA). Disposable Ag/AgCl surface
electrodes (Blue Sensor, Medicotest A/S, Ølstykke, Denmark) were used. The raw surface
EMG signals were preamplified (overall gain 1000, common mode rate rejection ratio 115
dB; filtered to produce a bandwidth of 10 - 500 Hz) and analog-to-digital conversion (12bit resolution) was at 1000 Hz.
FIGURE 1 Photographs illustrating exercises 8, 9, 25 and 26 (maximal voluntary isometric contractions and
endurance exercises)
134
Reliability of a functional clinical test battery
FIGURE 2 Photographs illustrating exercises 12, 14, 21 and 22 (stabilization exercises)
Data analysis
Postural control
The vertical ground reaction forces were used to calculate the position of the center of
pressure and the equivalent center of gravity sway angles. The center of pressure excursion
(sway velocity in degree per second) was used for further analysis.
Proprioception
The three-dimensional data were processed with the BioAnalyse software program (version
2.0, BioMatt) to calculate the lumbar lordosis. The lumbar lordosis angle was determined as
the angle between the lines connecting the spinous process of L1 and L3 and the line
connecting the spinous process of L3 and L5.
The repositioning error (in degrees) was evaluated by calculating the difference between the
angle of the lumbar lordosis position set by the tester and the angle of the lumbar lordosis
position assumed by the subjects themselves.
135
Chapter 6
Muscle activity
The stored surface EMG data were full-wave rectified and smoothed. The static phases of
the exercises were analysed using an interval of 2500 msecs after the defined starting point
of the holding position. The mean averaged root mean square value (in microvolts) of the
three repetitions was used for further analysis.
In the analysis of the endurance data, the EMG recordings were divided into 5-sec epochs,
and a fast Fourier transform was applied to each epoch to obtain a frequency amplitude
spectrum. The relative decrease (slope) in median frequency, defined as the frequency that
divided the spectrum into two equal areas, was calculated. The endurance time was also
measured. The Noraxon MyoResearch 2.10 software package was used.
Statistical analysis
Statistical analysis was performed using the SPSS 11.0 software package (SPSS, Chicago,
IL) for Windows. The intraclass correlation coefficient (ICC) model 2,3 was used.
According to Bartko,7 ICC values in the range 80-100% indicate “excellent repeatability”,
those from 60-80% “good repeatability”, and those < 60% “poor repeatability”.
To objectively identify reliability, it is suggested to combine ICC calculations (which
represent a relative measure of reliability) with the standard error of the measurement
(SEM) (which quantifies the precision of individual scores on a test and is referred to as the
typical error).8 To enhance interpretation of the SEM values, the SEM as a percentage of
the grand mean (%SEM) was calculated. 9
RESULTS
Repeatability
The sway velocity data, representing the postural control, showed good repeatability (ICC
0.68-0.90; %SEM 4.04-9.50), and proprioception values in sitting (ICC 0.67; %SEM 9.71)
and standing (ICC 0.61; %SEM 9.38) were also reliable.
Table 1 presents the ICC values and the %SEM calculations for the EMG amplitudes
during exercises 7 - 24 and for the frequency and time parameters during the endurance
exercises 25 and 26. Good to excellent repeatability was demonstrated (ICC 0.60-0.98;
%SEM 0.004-19.94).
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Reliability of a functional clinical test battery
Reproducibility
The reproducibility study resulted in ICC and %SEM values similar to those of the
repeatability study.
Data on postural control showed good, reliable results (ICC 0.67-0.85; %SEM 3.44-9.24).
The reproducibility of the repositioning error, representing proprioception, was also good
(ICC 0.60-0.68; %SEM 9.98-13.56). The EMG data and time data in the reproducibility
study showed good to excellent reproducibility (ICC 0.61-0.95; %SEM 0.004-17.73). Table
2 presents the data on reproducibility.
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Chapter 6
TABLE 1 Repeatability (intraclass correlation coefficient [ICC]and standard error of the measurement as a percentage of the grand mean [%SEM] values) for the
mean electromyographic amplitude measure (root mean square values) of the abdominal and back muscles in exercises 7-26.
IO-L
IO-R
EO-L
EO-R
MF-L
MF-R
ICLT-L
ICLT-R
ICC
%SEM
ICC
%SEM
ICC
%SEM
ICC
%SEM
ICC
%SEM
ICC
%SEM
ICC
%SEM
ICC
%SEM
0.88
8.68
0.87
8.32
0.80
8.35
0.66
12.16
0.90
4.21
0.92
3.85
0.97
3.14
0.95
3.33
0.67
0.92
7.37
4.22
0.81
0.87
5.09
5.96
0.83
0.96
6.83
3.69
0.76
0.93
5.86
5.18
0.91
0.84
7.32
8.08
0.93
0.79
7.51
7.03
0.64
0.75
8.93
10.23
0.61
0.66
7.78
9.16
0.75
0.82
0.86
0.60
0.72
0.91
0.88
0.88
0.68
0.77
0.02
0.02
5.73
8.55
10.71
6.33
6.14
6.49
6.18
7.55
0.93
0.76
0.88
0.84
0.84
0.90
0.86
0.90
0.75
0.78
0.006
0.03
8.06
9.53
5.77
6.12
6.84
5.30
7.59
6.46
0.94
0.94
0.95
0.71
0.83
0.95
0.91
0.94
0.88
0.63
0.03
0.03
3.98
8.45
9.08
3.85
4.69
3.97
4.52
6.38
0.83
0.67
0.76
0.95
0.73
0.88
0.76
0.86
0.88
0.82
0.07
0.24
5.95
5.84
9.30
5.89
5.53
4.24
4.32
8.69
0.93
0.95
0.94
0.66
0.61
0.94
0.89
0.97
0.84
0.94
0.006
0.008
3.12
5.16
10.66
3.83
3.76
2.56
6.52
4.41
0.95
0.94
0.97
0.76
0.86
0.97
0.97
0.97
0.90
0.92
0.006
0.004
3.06
10.71
2.75
2.82
3.80
3.24
5.85
5.56
0.83
0.84
0.90
0.60
0.62
0.93
0.90
0.96
0.89
0.80
0.06
0.01
4.34
9.28
10.23
4.68
4.28
1.98
7.38
5.05
0.81
0.89
0.79
0.88
0.80
0.90
0.84
0.86
0.69
0.86
0.02
0.02
4.98
4.60
7.71
4.70
6.79
5.58
5.70
6.58
0.66
0.92
11.28
5.38
0.60
0.86
11.55
7.67
0.83
0.96
8.00
3.91
0.65
0.85
9.56
7.10
0.93
0.94
4.26
2.54
0.91
0.91
5.20
2.37
0.89
0.95
4.34
2.80
0.81
0.87
6.14
4.92
0.85
11.98
0.80
14.69
0.83
10.49
0.90
8.23
0.85
0.84
4.43
7.26
0.85
0.77
4.43
7.44
0.85
0.87
4.43
10.76
0.85
0.79
4.43
11.48
MVICs
exercise 7-9
Coordination
exercise 10
exercise 11
Stabilization Type I
exercise 12
exercise 13
exercise 14
exercise 15
exercise 16
exercise 17
exercise 18
exercise 19
exercise 20
exercise 21
Stabilization Type II
exercise 22
exercise 23
Flexion-Relaxation
exercise 24
Endurance
exercise 25-26
Time
Slope median
frequency
0.98
0.70
3.16
19.94
0.98
0.84
3.16
9.99
0.98
0.76
3.16
15.81
0.98
0.68
3.16
19.89
L, left; R, right; IO, internal oblique; EO, external oblique; MF, lumbar multifidus; ICLT, thoracic part of the iliocostalis lumborum; MVIC, maximal
voluntary isometric contraction.
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Reliability of a functional clinical test battery
TABLE 2 Reproducibility (intraclass correlation coefficient [ICC]and standard error of the measurement as a percentage of the grand mean [%SEM] values)
for the mean electromyographic amplitude measure (root mean square values) of the abdominal and back muscles in exercises 7-26.
IO-L
IO-R
EO-L
EO-R
MF-L
MF-R
ICLT-L
ICLT-R
ICC
%SEM
ICC
%SEM
ICC
%SEM
ICC
%SEM
ICC
%SEM
ICC
%SEM
ICC
%SEM
ICC
%SEM
0.87
7.01
0.91
5.39
0.82
7.67
0.86
7.15
0.90
3.79
0.83
4.76
0.90
3.53
0.86
4.77
0.90
0.93
7.52
10.93
0.70
0.94
9.02
7.88
0.74
0.84
9.35
8.19
0.73
0.72
13.40
11.35
0.67
0.71
11.22
11.64
0.75
0.63
8.21
14.05
0.84
0.66
7.16
8.63
0.91
0.89
6.16
8.23
0.87
0.84
0.87
0.77
0.83
0.92
0.89
0.90
0.75
0.86
0.02
0.02
8.40
7.84
8.91
7.96
8.53
9.03
6.56
7.71
0.89
0.85
0.87
0.87
0.72
0.81
0.86
0.90
0.86
0.65
0.01
0.02
8.22
8.30
9.42
14.94
9.00
8.15
9.61
7.10
0.82
0.60
0.68
0.84
0.85
0.65
0.86
0.62
0.87
0.69
0.06
0.08
9.79
6.41
9.07
10.37
5.53
10.07
5.95
5.32
0.73
0.81
0.83
0.86
0.80
0.84
0.88
0.89
0.81
0.91
0.04
0.03
9.55
8.34
7.50
8.79
8.87
7.36
6.55
4.74
0.80
0.80
0.95
0.77
0.86
0.90
0.89
0.92
0.90
0.94
0.01
0.01
2.60
6.21
7.34
4.94
4.67
3.67
6.26
4.30
0.73
0.71
0.82
0.78
0.90
0.80
0.91
0.87
0.89
0.87
0.01
0.01
4.81
7.25
4.26
6.00
5.33
4.50
6.16
6.47
0.68
0.84
0.84
0.84
0.81
0.79
0.92
0.89
0.76
0.78
0.02
0.008
5.32
8.85
5.47
7.03
3.98
4.11
10.60
7.82
0.90
0.81
0.89
0.68
0.87
0.91
0.69
0.91
0.64
0.91
0.004
0.02
4.35
5.22
10.06
5.42
8.63
4.42
10.96
7.80
0.63
0.88
13.32
10.61
0.70
0.72
12.78
12.99
0.79
0.62
13.62
12.07
0.78
0.83
13.56
10.68
0.85
0.91
7.36
5.33
0.85
0.92
8.36
4.50
0.91
0.74
5.27
7.25
0.84
0.86
6.71
6.52
0.62
13.34
0.70
14.25
0.89
7.58
0.94
6.37
0.73
0.81
6.41
8.78
0.73
0.72
6.41
10.56
0.73
0.69
6.41
9.11
0.73
0.61
6.41
17.73
MVICs
exercise 7-9
Coordination
exercise 10
exercise 11
Stabilization Type I
exercise 12
exercise 13
exercise 14
exercise 15
exercise 16
exercise 17
exercise 18
exercise 19
exercise 20
exercise 21
Stabilization Type II
exercise 22
exercise 23
Flexion-Relaxation
exercise 24
Endurance
exercise 25-26
Time
Slope median
frequency
0.83
0.86
8.61
15.24
0.83
0.81
8.61
10.46
0.83
0.75
8.61
12.89
0.83
0.80
8.61
10.74
L, left; R, right; IO, internal oblique; EO, external oblique; MF, lumbar multifidus; ICLT, thoracic part of the iliocostalis lumborum; MVIC, maximal
voluntary isometric contraction.
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Chapter 6
DISCUSSION
To assess the interacting components of functional stability, a functional test battery
requires reliable and consistent responses. The present study investigated the repeatability
and reproducibility of postural control, proprioception, and muscle activity measurements.
All components demonstrated good to excellent repeatability and reproducibility.
Postural control
Although a test duration of 10 secs was reported to be the least realiable10, evaluation of
postural control by means of a 10-sec unilateral stance test on a force platform as
performed in the present study is repeatable and reproducible.
Proprioception
The repeatability and reproducibility of the repositioning error in the present study confirm
the results of Brumagne et al.,11 who used a similar test protocol with pelvic movements
and lumbar spine repositioning. However, in contrast to the ultrasound movement analysis
system used in the present study, they worked with a piezoelectric accelerometer.
Muscle activity
The repeatability and reproducibility of the averaged EMG data were generally good to
excellent (considering both ICC and %SEM indices) during all exercises of this clinical test
battery.
The generally high correlation scores of the maximal voluntary isometric contractions were in
accordance with the finding that the level of contraction force influences the repeatability
and reproducibility. It has been shown that the higher the force, the better the reliability.12
In general, the muscle activity reliability values of the coordination exercises were slightly lower
than those of the maximal voluntary isometric contractions. This could be attributed to the
relatively low activity in the sitting and standing posture. This low activity could also easily
be influenced by small changes in posture and subsequent stability demands on the trunk
muscles.13 Nevertheless, excellent repeatability for the back muscle EMG signals during
quiet stance13 and excellent repeatability and reproducibility during standing with a neutral
lumbar spine position3 have been demonstrated in similar studies.
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Reliability of a functional clinical test battery
In stabilization exercises with arm movements (in sitting as well as in standing) the local trunk
muscles showed better repeatability and reproducibility than the global trunk muscles.
In both the repeatability and the reproducibility study, the %SEMs of the unilateral arm
movements in the sitting position were exceptionally low (0.004-0.24), representing better
test stability than was indicated by the ICCs. Based on these results, this exercise can be
considered to be the best repeatable and reproducible exercise of all the clinical tests
analysed in this particular test battery.
In general, the repeatability and reproducibility of the trunk EMG data during stabilization
exercises with leg movements were good, but not as good as during stabilization exercises with
arm movements.
During the stabilization exercises with trunk movements the back muscles showed better ICC
values and lower %SEM values compared to the abdominal muscles. This could be due to
the higher activity levels of the back muscles compared with the abdominal muscles during
the static phase with the forward leaning trunk position.
Testing the ability to relax the back muscles is important because the flexion-relaxation
phenomenon is often used to discriminate patients from healthy controls. Similar to the
results of Watson et al.,14 in our study the repeatability of the flexion-relaxation
phenomenon was excellent. Neblett et al.15 also reported high repeatability and
reproducibility correlations in healthy subjects.
Similar to the repeatability study of Dedering et al.,16 describing a static back endurance
modified Biering-Sørensen test, in the present study ICC values of the total median
frequency slope ranged from 0.77 to 0.87 and the %SEM values ranged from 7.26 to 11.48.
In accordance with our reproducibility results, Larivière et al.17 demonstrated that the
results of the more lateral muscles (thoracic part of the iliocostalis lumborum in the present
study) were generally less reliable than the corresponding EMG indices obtained with more
medially located muscles (lumbar multifidus in the present study). The lumbar multifidus,
as a local muscle, was characterized by optimal endurance qualities and seemed to be
preferentially selected during extension tasks. In contrast, the lateral muscles seemed to be
active in the frontal and transverse planes during extension tasks,18 and as global muscles,
they were better qualified to create powerful movements for a shorter period of time.
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Chapter 6
In both the repeatability and reproducibility study, the %SEM values of the time variable
are smaller than those of the slope median frequency parameters of the abdominal and the
back muscle endurance test. This supports the use of these tests in a clinical test condition
requiring only an appropriate bench and a stopwatch.
Limitations of the study
In the present study, as in most other reliability studies, subjects without any pain in the
lower back were studied. Consequently, the repeatability and reproducibility results are only
applicable to healthy subjects. The reliability of the results from chronic LBP patients could
be lower because they may not perform the tests maximally due to fear of (re)injury19 and
pain. Use of the current clinical test battery in patients with chronic LBP would probably
require additional questionnaires in order to understand the pain, thoughts and behavior of
these patients and thus better interpret the test results.
CONCLUSION
In the present study, the clinical test battery, based on the different components of
functional spinal stability, was shown to be a reliable tool in the evaluation of healthy
subjects. The evaluation of postural control, proprioception and muscle activity
(coordination, stabilization, MVIC, endurance and flexion-relaxation) showed good to
excellent repeatability and reproducibility. Further analysis of all these parameters in a
clinical setting, particularly in patients with low back pain, therefore seems appropriate.
Acknowledgements
The authors thank Ms. Daisy De Proft, Ms. Carla Franco, Ms. Mieke Haeck and Ms.
Isabelle Heylbroeck for their assistance with the collection of the data. They also thank Mr.
Pascal Coorevits for the statistical advice and Ms. Iris Wojtowicz for the linguistic
corrections.
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Reliability of a functional clinical test battery
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144
CHAPTER 7
THE EFFECTIVENESS OF SPECIFIC EXERCISE THERAPY
VERSUS DEVICE EXERCISE THERAPY IN THE TREATMENT
OF CHRONIC LOW BACK PAIN PATIENTS
Veerle K. Stevens1, Geert Crombez,2, Thierry G. Parlevliet,3, Filip A.
Descheemaeker1, Katie G. Bouche1,3, Guy G. Vanderstraeten1,3, Lieven A. Danneels1
1
Department of Rehabilitation Sciences and Physiotherapy; Faculty of Medicine and
Health Sciences, Ghent University, Ghent, Belgium.
2
Department of Experimental Clinical and Health Psychology, Faculty of Psychology and
Educational Sciences, Ghent University, Ghent, Belgium.
3
Department of Physical Medicine and Orthopaedic Surgery, Faculty of Medicine and
Health Sciences, Ghent University, Ghent, Belgium.
Under review in European Spine Journal
145
Chapter 7
ABSTRACT
Two popular rehabilitation programs for chronic low back pain are specific exercise
therapy and device exercise therapy. However, adequate comparison of both active
approaches is lacking. Chronic nonspecific low back pain patients with a motor control
impairment were included in this clinical trial. Randomization referred 39 patients to 18
sessions of specific exercise therapy (specific lumbar stabilization therapy + minimal
manual therapy and education) and 39 patients to device exercise therapy (specific lumbar
training devices). A clinical functional test battery, an isokinetic trunk strength test and
several functional disability, pain, health and psychosocial questionnaires were completed at
baseline and after the intervention period. The clinical test battery evaluated postural
control, proprioception and electromyographical trunk muscle activity during different lowand high intensity exercises. One-year follow-up was obtained by telephone questionnaire.
The results of this clinical trial demonstrated that relative lumbar multifidus activity was
increased in both active therapy groups, but more in the specific exercise group than in the
device exercise group. The endurance capacity of the abdominal muscles increased in both
groups, as well as the flexion and extension peak torque. Overall, pain, disability, and
quality of life improved in both groups. Physical and social functioning significantly
improved in the specific training group, but less or no change was reported in the device
exercise group. In both groups, functional disability further decreased even at 1-year
follow-up. The decreased levels of pain intensity immediately after treatment were
maintained at 1-year follow-up in both groups.
In conclusion, 18 treatment sessions of specific exercise therapy or device exercise therapy
improved trunk strength torque, relative lumbar multifidus activity, abdominal endurance
capacity and psycho-social status and health of chronic low back pain patients with a motor
control impairment. Limited evidence was found to recommend specific exercise therapy
over device exercise therapy.
KEY WORDS
Low back pain – Rehabilitation – Exercise – Motor Control – Devices
146
Specific exercise therapy versus exercise therapy on devices
INTRODUCTION
European guidelines recommend exercise therapy as a first-line treatment in the
management of chronic low back pain (CLBP) [3]. Specific exercise therapy and device
exercise therapy are often used active rehabilitation methods. Specific exercise therapy
focuses on the findings of the clinical examination and the daily needs and work
complaints of the patient. In the present study, specific exercise therapy consists of motor
control stabilization therapy. Various studies show that specific lumbar stabilizing therapy
as a single therapy or combined with other treatments reduces pain intensity and disability
in low back pain [7,14,24,28,38,40,41,44,48,52,66] and in pelvic girdle pain patients [63,64],
and prevents recurrent pain episodes [18,44,48].
Device exercise therapy allows the patients to train on their own, once the clinical
examination is done and the individual training is programmed. This training as a single
therapy [16,23,27,33-36,53] or combined with functional muscle and coordination
exercises, behavioural support and ergonomic advice [22,67,68] or combined with
education and aerobic and strength training of other muscles [39] improves pain intensity
and physical impairment [22,33-35,53,67] and increases lumbar muscle endurance [22,36]
and trunk flexion [27,36,67] and extension [16,27,36,39,53,67] strength.
There is no adequate comparison of both interventions at this moment. Due to the
common clinical application, this is however important. The European guidelines
recommend research to determine the effectiveness for specific target groups [3]. The main
aim of the present study was to investigate the effect of 2 active 18-sessiontreatment
programs on chronic non-specific low back pain patients with motor control impairment.
MATERIALS AND METHODS
Participants
Eighteen to 65-year-old study participants were recruited at the department of physical
medicine and orthopaedic surgery of the University Hospital of Ghent. Aspecific low back
pain patients with a history of more than three pain episodes during the past year or pain
persisting for at least three months were invited to participate in the study. The physician
performed a clinical examination and when needed, additional investigations were asked for
147
Chapter 7
to assure that no identifiable specific anatomical or neurophysiological causative factors
were present. A musculoskeletal therapist performed a clinical investigation to determine
whether motor control impairment was present [42]. Motor control impairment is
associated with impairment or deficits in the control of the symptomatic spinal segment in
the primary direction of pain. Pain in these disorders is associated with a loss of functional
control around the neutral zone of the spinal motion segment due to specific
motor control deficits (and muscle guarding in some situations) of the spinal muscles.
These disorders frequently present in a directional manner (flexion, extension (passive or
active) and lateral shift control impairment), as well as in combinations of these directions
(multi-directional control impairment) [42,43].
Exclusion criteria were: specific LBP, such as tumors, fractures, infections, spinal stenosis,
spinal malformations; radicular symptoms (radiating pain below the buttock, loss of
sensation, muscle dysfunction or loss of reflexes); organic lesions; neurologic or systemic
conditions; spinal surgery; pregnancy. Also highly distressed patients were excluded
because research has shown less favourable outcomes for this subgroup [21]. We used the
cutt-off criteria of the Distress Risk Assessment Method (DRAM). The DRAM includes
the Modified Zung Questionnaire (MZQ) and the Modified Somatic Perception
Questionnaire (MSPQ). Patients with a score of more than 33 on the MZQ, defined as
distressed depressive or a MZQ score between 17 and 33 and a MSPQ score higher than
12, defined as distressed somatic patients [30] were excluded.
A flow diagram summarizing the study design is presented in Figure 1. All patients signed
informed consent in ignorance of the group assignment. Ethical approval had been
obtained from the Ethics Committee of the Ghent University Hospital.
148
Specific exercise therapy versus exercise therapy on devices
Patients send by the physician
N = 239
Excluded (N = 161)
- no motor control impairment (N = 118)
- refused to participate (N = 29)
- DRAM too high (N = 14)
Randomised (N = 78)
Allocated to specific exercise
therapy (N = 39)
Drop out during intervention (N = 6)
- combination therapy and work situation no
longer possible (N = 4)
- not motivated any more (N = 1)
- complaints did not decrease as quickly as
expected (N = 1)
Allocated to device exercise
therapy (N = 39)
Drop out during intervention (N = 7)
- combination therapy and work situation no
longer possible (N = 3)
- not motivated any more (N = 2)
- complaints did not decrease as quickly as
expected (N = 2)
Analysis post intervention (N = 33)
Analysis post intervention (N = 32)
Drop-out due to changed phone number and/or address
Analysis 1-year follow-up (N = 29)
Analysis 1-year follow-up (N = 30)
Figure 1. Flow chart summarizing the study design
Interventions
Prior to the commencement of the study, it was determined that in chronological order of
acceptance into the study, each patient would be assigned a number. Patients with an odd
number were directed to specific exercise therapy and patients with an even number
followed device exercise therapy. Administrative staff without knowledge of the study
protocol electronically arranged the patient’s appointments to ensure the objectiveness.
The rehabilitation program included 18 individual sessions during 12 weeks (2 times per
week during the first 6 weeks and 1 time per week during the next 6 weeks). Due to the
Belgian insurance system of contribution to physiotherapy costs, 18 treatment sessions are
most common in Belgium. All patients were given therapy sessions of approximately 45
minutes. Musculoskeletal therapists guided the sessions.
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Chapter 7
Specific exercise therapy
The specific exercise therapy consisted of 90% motor control stabilization exercises
[31,49,50,51,56] and 10% manual therapy (mobilization and soft tissue techniques) and
education. Manual therapy and education aimed to enhance the effects of the specific
exercise intervention [49].
This motor control approach aimed to train the integration of the so-called local and global
muscle systems, and to progress through a program of functional exercises in varying
environments and contexts that were tailored to the needs of the patients. There were also
functional exercises directed to the patients’ needs. These exercises were practiced in
different environments and contexts to maximize transfer to daily situations [20]. The
classification into a local and global muscle system is based on anatomical and functional
diversity [5]. The deeper local muscles such as transversus abdominis (TA), lumbar
multifidus (MF) and the pelvic floor muscles seem responsible for the control of the
buckling forces and the overall orientation of the spine and pelvis on the one hand, and
for the control of intervertebral translation and rotation during trunk movement on the
other hand [20]. The global muscle system is thought to be responsible for global stability
and producing torque. The treating musculoskeletal therapist (8 years of experience in
treating motor control problems) was free to choose the type of exercises and the
progression he felt most suitable for the individual patient. The patients were observed and
guided closely by the therapist during each session.
The treatment process contained a clear line of progression achieved by changing
parameters such as postural load, reduction of attention demands, reduction of speed, or
additional strategies to augment performance [20] with the final goal to obtain functional
improvement. Daily home exercises were encouraged. Compliance with the home program
was not assessed [38].
Device exercise therapy
Four lumbar back training units (flexion, extension, lateral flexion and rotation) were used
to rehabilitate trunk muscle function and coordination (Tergumed® Line for the back,
Proxomed®, Alzenau, Germany). Restraining mechanisms and lever arm attachments were
adjusted to the subject’s body dimensions, in accordance with the manufacturers’
instructions. A posterior pelvic pad, a belt and thigh pads secured the position of the lower
limbs and pelvis.
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Specific exercise therapy versus exercise therapy on devices
The exercise program was based on the patient’s results of isometric strength and mobility
measured on the devices during the first and the 10th treatment session. The increase in
torque in the 10th session compared with the first session was 23.76% (SD 50.28), 4.05%
(SD 17.87), 38.47% (SD 42.95), 31.97% (SD 30.43), 27.48% (SD 45.09) and 42.90% (SD
46.75) for extension, flexion, left and right lateral flexion and left and right rotation,
respectively. Maximal isometric strength was determined in a neutral upright sitting
position.
The treatment program started with a minimum of 4 isometric training sessions. Visual
feedback presented as a sinusoidal curve on a notebook, indicating required time and force
(30 to 40 % of maximal), supported the controlled performance of the isometric exercises.
The patient performed 3 sets of 6 repetitions with a pause of 45 seconds in between. Test
and detailed training results of each patient were saved on a notebook connected to each
device.
After the isometric training sessions, the patient performed dynamic movements with a
gradual increase in weight resistance from about 12% to 70% of maximal force concerning
the flexion and extension movements and from about 12% to 55% of maximal force
concerning the rotation and lateral flexion movements. Visual feedback was presented as a
sinusoidal curve on a notebook, indicating required time and range of motion (ROM) (80%
of maximal ROM) and supported the controlled performance of the dynamic exercises.
Three sets of 6 to 12 repetitions were performed with a pause of 45 to 60 seconds in
between.
Prior to each training session, 10 minutes warming-up on an exercise bicycle were
performed and at the end of each session 4 different stretching exercises (a rotational
stretching in crook-lying by turning over both legs, a standing stretching exercise for the
latissimus dorsi and 2 stretching exercises for the lumbar extensors in supine and fourpoint kneeling) were repeated 3 times for 30 seconds. The therapists were instructed not to
give any additional information to the patients.
Outcome Measurements
Patients performed physical functioning tests and filled in several questionnaires at baseline
and at the end of the treatment. At follow-up there was a short telephone survey.
151
Chapter 7
Functional clinical test battery
The functional clinical test battery evaluated postural control on a force plate, positionreposition accuracy of the lumbar spine using an ultrasound movement analysis system and
trunk muscle activity through surface electromyography.
Trunk muscle activity was investigated during six categories of exercises: maximal voluntary
isometric contractions (MVIC), coordination exercises, stabilization exercises with upper
and lower limb movements, stabilization exercises with trunk movements, abdominal and
back muscle endurance tests and a full trunk flexion exercise to analyze the flexionrelaxation capacity of the back muscles. The complete description of all exercises,
equipment and data analysis are reported in a manuscript reporting the reliability of this test
battery [60]. Because debate exists on the use of MVIC exercises for EMG signal amplitude
normalization purposes in low back pain patients [9], the mean amplitudes during
standardized submaximal exercises (first 2500 ms of the static endurance tests) were used.
To facilitate the interpretation of the EMG data of the different tests, data concerning
similar exercises in the same position were averaged. Averaging measures increase the
reliability of the EMG indices [26].
In addition, the trunk flexion and extension peak torque were measured using an isokinetic
dynamometer (Biodex System 3, New York, US). The test was conducted in a seated
position at 60°/s. The pelvis and distal thighs were stabilized by Velcro straps. The
leverarm axis was aligned with the L4-L5 intervertebral space. Anterior belts along both
shoulders and in front of the chest and a pad distal to the scapular spines were used as
force pads. Testing was performed along a ROM of 40°, from -10° (extension) to 30°
(flexion) [12].
Questionnaires
Functional disability
The Quebec Back Pain Disability Scale (QBPDS) is a 20-item instrument and assesses
functional disability. Each item is scored on a scale from 0 to 5. The maximum score of
100 represents maximum disability. The Dutch language version of the QBPDS was shown
to be a reliable and valid instrument for assessing functional status in patients with LBP
[57]. This scale was used at baseline, immediately after the intervention and at 1-year
follow-up.
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Specific exercise therapy versus exercise therapy on devices
Pain
At baseline, after the intervention and at 1-year follow-up, the patients were asked to
indicate the average pain intensity over the past week (0-10).
The Multidimensional Pain Inventory – Part One (MPI-I) measured several domains of
pain: pain severity (3 items), interference with the daily life due to pain (11 items),
perceived life control (4 items), affective distress (3 items) and social support (3 items).
Each item obtained a score between 0 and 6. Good scores involved high scores on
perceived life control and social support and low scores on pain severity, interference with
the daily life due to pain and affective distress. The Dutch version was proven reliable and
valid [29].
Psycho-social status
The Pain Catastrophizing Scale (PCS) is a 13-item instrument which assesses the tendency
to focus excessively on pain sensations (rumation), to magnify the threat value of pain
sensations (magnification), and to perceive oneself as unable to control the intensity of pain
(helplessness) [65]. Scores between 0 and 52 can be obtained. A score of ≥ 24 seems
predictive for CLBP [46]. The original factor structure of the PCS with the subscales
rumination, magnification and helplessness is supported in CLBP Dutch-speaking samples
[70].
Fear of movement/injury or reinjury was measured using the 17-item Tampa Scale of
Kinesiophobia (TSK), a scale determining the level of a person’s fear to perform physical
movement and activities resulting from a feeling of vulnerability to painful injury or
reinjury. Minimal and maximal scores are 17 and 68. If the score on the TSK is larger than
the median of 40, it appears worth inquiring about the essential stimuli of the fear [8]. In a
CLBP sample construct validity and predictive validity of the Dutch language version of
the TSK subscales were supported [55]. Reverse items (item numbers 4, 8, 12 and 16) were
omitted [15].
The Hospital Anxiety and Depression Scale (HADS) is a 14-item scale designed to detect
anxiety and depression, independent of somatic symptoms. Scores range from 0 to 42
(maximum 21 for each subscale). A score of ≥ 11 on each of the subscales (anxiety and
depression) seems to indicate the probable presence ('caseness') of the mood disorder [58].
153
Chapter 7
Validity was reported to be good in different populations [6]. Homogenity and test-retest
reliability of the Dutch language version of the HADS was demonstrated to be good [59].
General health status
The value of the SF-36 is that the patient’s changing health perception can be tracked over
time to determine the success of rehabilitation and intervention [27]. For each dimension,
item scores are coded, signed, and transformed into a score from 0 (worst health) to 100
(best health) (manual SF-36). The Dutch language version of the SF-36 has proven to be a
practical, reliable, and valid instrument for use in studies of chronic disease populations [2].
Therapy Satisfaction
In addition to the above mentioned questionnaires, the patients were asked to indicate their
overall satisfaction with the program on a visual analogue scale of 10 cm (0 = not satisfied
at all; 10 = completely satisfied with the therapy).
One-year Follow-up Outcome Measurements
One year after the end of the intervention, patients were telephoned and asked for their
current work situation, drug use, work absenteeism due to LBP, other received therapies,
exercise compliance, pain intensity and functional disability (QBPDS).
Statistical Analysis
Statistical analysis was performed using the SPSS 12.0 software package (SPSS Inc.,
Chicago, IL) for Windows. The level for statistical significance was set at α = 0.05.
Changes in variables in the two groups pre and post therapy were assessed using a twofactor analysis of variance (ANOVA) with repeated measures (group x time of assessment).
When the interaction was significant, least significance difference tests, adjusted by a
Bonferroni test to protect against type I errors, were used.
Based on the primary outcome measure QBPDS, the current study achieved 73% power to
detect between group and time differences.
RESULTS
Table 1 details the demographic data for the 2 groups after randomization.
154
Specific exercise therapy versus exercise therapy on devices
Table 1. Baseline characteristics of patient population.
Specific therapy group
N = 33
Device therapy group
N = 32
Age
Mean (SD)
32.27 (11.97)
39.87 (12.30)
Body Mass Index
Mean (SD)
23.14 (3.57)
22.84 (3.45)
39.39%
60.61%
25%
75%
45.91 (79.74)
44.04 (49.70)
Marital status
* maried
* living together
* boy/girlfriend
* divorced
* widow(er)
* living alone
39.39%
9.09%
3.03%
6.06%
3.03%
39.39%
40.62%
9.37%
3.12%
9.37%
0%
37.50%
Education level
* primary school
* comprehensive school
* secondary school
* higher education
3.03%
12.12%
33.33%
51.51%
3.12%
9.37%
31.25%
56.25%
Current status
* working outside
* housewife/houseman
* student
* unemployed
* insurance compensation
60.61%
3.03%
24.24%
16.06%
6.06%
81.25%
3.12%
9.37%
3.12%
3.12%
37.55 (4.37)
34.77 (10.22)
12.12%
18.75%
57.57%
2.21 (1.68)
50%
2.12 (1.5)
Gender
* male
* female
Duration CLBP in months
Mean (SD)
Hours working/week
Mean (SD)
Smoking
Sport recreative
Mean (SD) hours sport/week
155
Chapter 7
Functional clinical test battery
Tables 2 and 3 present the data concerning the functional clinical test battery.
The data concerning the proprioception and the postural control after therapy did not differ
significantly from the data before therapy.
The EMG data showed significant higher relative activity after therapy in both groups for
the external abdominal oblique (EO) and the thoracic part of the iliocostalis lumborum
(ICLT) during the MVIC exercises and for the internal oblique (IO) during the stabilization
exercises with upper limb movements in standing. The MF demonstrated significant higher
relative activity in both groups during the MVIC, the stabilization exercises with lower limb
movements in sitting and the stabilization exercises with trunk movements in standing. A
tendency to significant increased relative MF activity (p = 0.06) was found in seated
stabilization exercises with trunk movements. After specific exercise therapy, but not after
device exercise therapy, the MF showed higher relative activity during the stabilization
exercises with lower extremity movements in standing and during stabilization exercises
with upper limb movements in both sitting and standing.
Concerning the endurance tests, in both groups the slope of the median frequency of the
IO and the duration of the abdominal endurance test were significantly improved after the
intervention period.
Flexion and extension peak torque increased significantly after both specific and device
exercise therapy.
156
Specific exercise therapy versus exercise therapy on devices
Table 2. Outcome data concerning postural control, proprioception, peak torque and endurance time for both active therapy groups.
Specific therapy
Mean
Pre
SD
Mean
Device therapy
Post
SD
P
Mean
Pre
SD
Mean
Post
SD
P
Postural control (°/s)
* unilateral left - eyes open
* unilateral left - eyes closed
* unilateral right - eyes open
* unilateral right - eyes closed
0.99
3.74
0.80
3.19
0.90
1.88
0.19
1.75
1.04
3.56
0.83
3.00
0.97
1.82
0.37
1.68
0.63
0.49
0.11
0.06
1.10
4.33
0.88
3.99
0.53
1.46
0.27
1.68
1.00
0.98
4.27
3.53
0.34
0.44
1.50
1.51
0.63
0.49
0.11
0.06
Proprioception (°)
* in sitting
* in standing
9.35
16.93
6.62
12.36
11.71
15.38
9.62
9.87
0.81
0.91
10.35
16.09
7.40
12.82
8.54
18.03
7.09
11.38
0.81
0.91
Peak torque (Nm)
* extension
* flexion
142.31
114.48
54.80
46.73
178.02
136.22
88.28
61.42
0.001
0.001
125.18
93.67
74.43
48.48
141.57
101.50
79.13
53.83
0.001
0.001
88532.81
99137.73
62336.76
36697.32
117956.31
111010.64
79370.50
43852.42
<0.001
0.43
78196.13
110334.28
51577.69
47196.47
94952.38
106513.03
62026.89
40254.13
<0.001
0.43
Endurance time (ms)
* abdominal
* back
157
Chapter 7
Table 3. Relative EMG activity (µV) during maximal voluntary isometric contractions (MVIC), coordination, stabilization, flexion-relaxation
and endurance exercises for both active therapy groups.
Specific therapy
Device therapy
Specific therapy
Device therapy
IO
Mean
Pre
SD
Mean
Post
SD
P
EO
Mean
Pre
SD
Mean
Post
SD
P
Mean
Pre
SD
Mean
Post
SD
P
Mean
Pre
SD
Mean
Post
SD
P
MVIC
338.57 427.54
340.51 261.89
0.41
257.55 131.50
304.78 211.77
0.41
219.67 124.08
227.20 68.81
0.02
191.39 102.71
236.00 133.76
0.02
Coordination exercises
* sitting
* standing
36.64
40.19
24.48
32.36
35.89
47.80
25.16
38.89
0.86
0.23
38.89
43.48
25.16
37.35
41.14
49.25
34.38
43.17
0.86
0.23
13.42
19.37
17.90
28.42
9.42
12.50
5.40
7.40
0.16
0.19
13.26
16.96
8.55
10.36
12.66
17.46
9.31
11.16
0.16
0.19
Stabilization exercises with upper limb movements
* sitting
* standing
32.20
43.00
22.75
33.35
41.36
55.28
37.18
41.77
0.12
0.03
35.95
44.76
25.35
33.97
40.59
57.82
33.33
52.22
0.12
0.03
14.13
18.28
19.44
23.96
10.86
14.84
6.41
9.75
0.52
0.85
12.90
15.81
7.84
9.76
13.98
18.47
9.22
11.84
0.52
0.85
Stabilization exercsises with lower limb movements
* sitting
* standing
68.54
74.96
28.52
34.70
67.38
73.89
28.24
36.04
0.51
0.49
74.03
74.47
49.70
38.92
80.71
81.95
46.39
35.63
0.51
0.49
22.76
25.57
16.98
15.92
19.55
24.53
7.96
14.23
0.86
0.63
22.84
27.80
12.42
15.5
25.50
30.26
16.21
17.64
0.86
0.63
Stabilization exercises with trunk movements
* sitting
* standing
27.08
31.80
23.88
28.34
29.75
33.85
20.76
29.42
0.39
0.43
25.80
30.56
26.27
27.58
27.55
34.19
19.84
25.50
0.39
0.43
13.88
14.12
22.20
24.64
9.16
10.58
9.55
8.20
0.27
0.58
9.17
12.31
6.82
8.8
9.70
13.32
7.81
11.27
0.27
0.58
-0.14
0.13
-0.06
0.22
0.01
-0.18
0.14
-0.14
0.09
0.01
-0.17
0.11
-0.12
0.09
0.54
-0.12
0.29
-0.13
0.11
0.54
Flexion-relaxation
Endurance
* Slope Median Frequency (Hz/s)
MF
MVIC
Pre
Mean
SD
177.39 50.23
Post
Mean
SD
194.44 68.86
ICLT
P
0.006
Pre
Mean
SD
192.2 63.79
Post
Mean
SD
217.35 77.18
P
0.006
Pre
Mean
SD
232.62 87.19
Post
Mean
SD
252.78 133.66
P
0.03
Pre
Mean
SD
232.44 95.03
Post
Mean
SD
257.81 95.86
P
0.03
Coordination exercises
* sitting
* standing
7.66
9.37
4.30
6.10
8.61
10.92
5.58
7.10
0.85
0.99
11.23
11.00
6.69
7.72
10.02
9.42
6.01
4.95
0.85
0.99
10.86
10.58
7.99
9.84
14.65
13.11
13.54
15.12
0.24
0.38
13.54
10.23
5.40
3.61
13.09
10.47
5.61
4.11
0.24
0.38
Stabilization exercises with upper limb movements
* sitting
* standing
22.54
34.87
7.90
10.86
26.83
40.43
10.82
13.57
0.003
0.006
29.08
39.77
7.74
10.88
27.53
38.91
9.65
10.87
0.28
0.67
39.44
39.61
23.47
15.15
44.62
42.12
34.23
13.15
0.63
0.63
45.76
48.06
12.3
12.75
44.15
47.41
11.09
10.81
0.63
0.63
Stabilization exercsises with lower limb movements
* sitting
* standing
11.6
19.37
5.23
9.31
13.65
22.6
6.60
12.14
0.02
0.009
12.39
20.02
4.26
8.91
13.06
19.81
4.86
8.43
0.02
0.86
12.20
16.54
6.75
7.72
14.12
21.15
12.47
15.28
0.45
0.13
13.35
21.04
5.12
13.05
13.36
21.04
6.22
17.56
0.45
0.13
Stabilization exercises with trunk movements
* sitting
* standing
32.93
42.14
17.96
20.32
39.95
51.48
18.17
20.93
0.06
0.01
41.46
49.6
21.66
20.96
41.95
52.99
22.39
20.00
0.06
0.01
43.84
52.2
18.76
22.57
51.21
81.77
20.45
121.8
0.15
0.16
51.52
60.87
13.93
20.75
50.66
61.65
12.23
18.11
0.15
0.16
Flexion-relaxation
20.88
20.51
20.32
20.12
0.57
31.32
29.13
29.28
26.62
0.57
20.53
18.45
23.12
23.29
0.56
29.99
28.98
24.31
21.59
0.56
Endurance
* Slope Median Frequency (Hz/s)
-0.38
0.26
-0.33
0.16
0.60
-0.26
0.19
-0.28
0.22
0.60
-0.14
0.19
-0.16
0.09
0.13
-0.12
0.21
-0.19
0.08
0.13
IO = internal abdominal oblique; EO = external abdominal oblique; MF = lumbar multifidus; ICLT = thoracic part of the iliocostalis lumborum
158
Specific exercise therapy versus exercise therapy on devices
Questionnaires
Table 4 shows the data of the several questionnaires.
Functional disability
The QBPDS demonstrated significant lower functional disability after therapy in both
groups. However, after therapy the QBPDS score was significantly lower in the specific
exercise therapy group compared with the device exercise therapy group.
Pain
The average pain over the past week decreased significantly after therapy in both groups.
The scores of all subscales of the MPI-I, the ‘social support’ subscale excepted, improved
significantly after both active interventions.
Psycho-social status
The total scores of the PCS, TSK and HADS decreased significantly after therapy in both
groups.
General Health status
The SF-36 demonstrated in both groups a significant higher score after therapy concerning
the ‘general health’, ‘vitality’, ‘lack of bodily pain’ and ‘role limitations due to physical
functioning’ subscales. The scores on the subscales ‘physical functioning’, ‘social
functioning’ and ‘health transition’ were significantly better after specific exercise therapy,
but not after device exercise therapy. No significant changes were reported concerning the
‘mental health’ and the ‘role limitations due to emotional problems’ subscales between
before and after therapy.
Satisfaction with therapy
The patients of the specific and the device exercises group showed therapy satisfaction of
7.20 (SD 2.24) and 6.03 (SD 2.79), respectively. There were no differences between groups.
159
Chapter 7
Table 4. Outcome measures concerning the questionnaires for both active therapy groups.
Mean
Quebec Back Pain Disability Scale
Pre
SD
Specific therapy
Post
Mean
SD
P
Mean
Pre
SD
Device therapy
Post
Mean
SD
P
30.39
14.75
20.70
13.85
<0.001
32.97
12.71
28.81
11.31
0.02
Multidimensional Pain Inventory
* pain severity
* interference with the daily life due to
pain
* perceived life control
* affective distress
* social support
7.64
3.94
5.18
4.24
<0.001
6.94
2.98
5.35
3.3
<0.001
26.97
15.76
5.79
11.11
19.95
4.02
3.38
5.69
16.42
17.64
4.27
10.32
12.72
4.01
3.01
6.30
<0.001
<0.001
0.05
0.95
21.61
15.77
5.35
9.77
10.17
4.54
3.64
5.43
15.55
17.23
4.87
10.62
8.92
4.41
4.06
5.09
<0.001
<0.001
0.05
0.95
Pain Catastrophizing Scale
18.39
10.64
13.10
11.55
0.001
17.06
9.15
15.55
8.85
0.001
Hospital Anxiety and Distress Scale
9.59
5.76
7.13
5.29
<0.001
9.35
4.81
7.52
4.82
<0.001
Tampa Scale for Kinesiophobia
37.12
8.05
31.79
8.05
<0.001
36.61
6.43
33.32
6.51
<0.001
SF-36 Health Inventory
* physical functioning
* role physical
* role emotional
* lack of bodily pain
* social functioning
* general health
* vitality
* mental health
* health transition
67.58
50.00
78.79
49.18
75.00
63.58
63.33
71.15
35.15
20.51
36.44
38.02
16.69
19.51
19.81
14.67
15.83
8.70
77.88
72.73
85.86
63.58
84.85
70.68
66.36
74.18
29.09
17.32
32.09
31.21
23.31
15.55
18.85
14.70
14.70
8.43
<0.001
<0.001
0.62
<0.001
0.005
<0.001
0.05
0.07
<0.001
65.81
54.84
84.95
49.65
81.05
63.35
58.71
69.94
27.42
16.08
41.54
27.00
17.84
20.63
23.97
18.75
18.87
9.99
69.35
70.97
82.8
57.87
80.24
67.94
62.42
72.77
25.81
16.06
38.24
35.35
20.72
23.00
23.67
20.04
20.17
9.23
0.11
<0.001
0.62
<0.001
0.82
<0.001
0.05
0.07
0.2
160
Specific exercise therapy versus exercise therapy on devices
One-year follow-up
The general information concerning the 1-year follow-up is demonstrated in Table 5.
In both groups, the pain intensity score at 1-year follow-up did not differ significantly from
the pain intensity score after the intervention, but was still significantly lower (p = 0.02)
than the pain intensity score before therapy (Table 6).
In both groups, the QBPDS further significantly decreased at 1-year follow-up (Table 6),
but no significant difference between the groups was demonstrated.
Table 5. Information obtained by telephone questionnaire at 1-year follow-up.
Specific exercise group
N = 29
Patients with changed job
Device exercise group
N = 30
0
1
Sick leave
Mean (SD) duration sick leave (days)
2
20 (14.14)
4
8.5 (8.18)
Other therapy for LBP
* infiltration
* ostepathy
* massage + electrotherapy
* massage + manipulation
* exercises + manual therapy
* acupuncture + whole body vibration
* medication
4
2
0
1
1
0
0
0
8
2
2
0
0
2
1
1
19
2.39 (2.20)
12
3.73 (2.69)
Continued doing exercises
Mean (SD) frequency exercises (days/week)
Table 6. Outcome pain intensity and functional disability (QBPDS) at 1-year follow-up for
both active therapy groups.
Pre
Post
1-year
Mean
SD
Mean
SD
P
Mean
SD
P
Pain
Specific exercise group
4.02
2.41
2.41
2.72
0.008
3.32
2.69
1.00
Device exercise group
4.37
2.16
3.74
2.61
0.008
2.97
2.12
1.00
QBPDS
Specific exercise group
32.39
14.10
22.93
13.65
< 0.001
13.14
11.33
< 0.001
Device exercise group
33.33
14.03
26.23
11.83
< 0.001
15.37
10.46
< 0.001
161
Chapter 7
DISCUSSION
The purpose of this study was to evaluate the effect of two forms of popular exercise
therapy on CLBP patients with motor control impairments.
Both exercise programs created decreased pain intensity and improved physical
functioning, general health, psychosocial status and several functional parameters.
Functional clinical test battery
The functional clinical test battery used in the present study included exercises of the
different components of functional stability: postural control, proprioception and muscle
activity during coordination and stabilization exercises, as well as during MVIC and
endurance exercises [60]. The flexion-relaxation capacity of the back muscles was also
evaluated. The EMG activity of the IO and MF was analysed to represent the so-called
local muscle system and the activity of the EO and the ICLT was representative for the socalled global muscle system [5]. The IO was expected to represent also the TA activity
since it was shown that medially and inferiorly to the anterior superior iliac spine, the fibres
of the transversus abdominis (TA) and IO are blended, so that a distinction between the
muscle signals cannot be made at this location [37]; also, at this site the direction of the
fascicles of both muscles is similar (inferomedial) [69].
The findings of the present study showed significantly increased relative MF activity during
all stabilization exercises after the intervention (concerning seated stabilization exercises
with trunk movements tendency to significant increase (p = 0.06)). However, the relative
MF activity during the seated stabilization exercises with lower limb movements and during
the stabilization exercises with upper limb movements, both in sitting and standing only
increased significantly in the specific exercise therapy group, but not in the device exercise
therapy group. Since the specific stabilizing therapy paid attention to the MF, TA and the
pelvic floor muscles, the results of this study show that 18 treatment sessions were
adequate to demonstrate significant increases in relative MF activity, but not in relative IO
activity. Only during stabilization exercises with upper limb movements in standing, the
relative IO activity increased significantly after both therapy interventions. O’Sullivan et al.
[45] investigated IO and rectus abdominis activity during an abdominal drawing in
manoeuvre before and after 10 weeks specific lumbar stabilization therapy. Nonnormalized
data showed a significant increase in IO activity, but in accordance to the findings of the
present study, data normalized to a submaximal exercise, showed no significant differences
162
Specific exercise therapy versus exercise therapy on devices
in IO activity. Although debate exists concerning the use of maximal or submaximal
exercises to normalize patient data, nonnormalized data are supposed inappropriate to
compare different patients and different test occasions [1]. Failure to normalize EMG data
before quantitative analysis was reported to introduce confounding variables not related to
muscle function (for example skin impedance, electrode orientation and amount of
subcutaneous tissue) [1,4].
During the stabilization exercises with trunk movements and during the stabilization
exercises with lower limb movements in standing the relative activity of the MF not only
increased in the specific exercise group, but also in the device exercise group. This finding
may be related to the fact that the device exercise therapy consisted of controlled
movements in different directions at predetermined velocities. In addition, recent research
in healthy subjects showed high relative MF activity when performing rotation, flexion and
extension exercises on these devices, even at low intensity levels [61,62]. Mannion et al. [35]
considered positive results in various active therapy groups to be attributable to generalized
increased activity rather than any specific changes in core stability. However, since only the
MF and in one case the IO showed significant differences during low-load exercises after
the interventions and not the so-called global muscles, specific localised training rather than
a general reconditioning seemed to have occurred. It should be noted that at baseline, the
subjects who dropped out of the device exercise therapy displayed significant higher
relative MF activity and significant lower EO and ICLT activity during some stabilization
exercises in comparison with the subjects who completed the device program.
In the early 90ties, strength and endurance were the main outcome measures in most active
treatment programs [32,47,54]. Recent studies reporting on the effect of specific
stabilization exercises often neglected these muscle properties, since strength increases
caused by low level exercises might not be expected to occur [7,14,18,19,28,38,40,41,44,45].
However, Koumantakis et al. [25] demonstrated significant muscle strength improvements
after stabilization training. In the present study, not only the MF activity, but also the
activity of the EO and ICLT increased significantly after both specific and device exercise
therapy. A qualitative indication of a relationship between the EMG and force is provided
by the observation that the EMG signal amplitude generally increases with higher force
and/or contraction velocity of the muscle [11]. The relation between EMG measurements
163
Chapter 7
of MVIC and force was supported in the present study since significant increases in flexion
and extension torque were reported in both groups. In accordance to these results, device
exercise therapy was reported to improve strength, but all researchers used the same
devices to test and to train [27,36,39,53,67]. However, in such case the cause of potential
between-group differences cannot be determined accurately due to familiarization with the
equipment for the patients attending device training. For that reason, isokinetic torque was
determined on another device that was only used for testing.
In the present study, the abdominal muscle endurance increased in both groups. Although
in general the relative IO activity was not changed during the low level testing exercises, the
endurance of this muscle seemed to be improved. No significant changes were present
concerning the endurance of the back muscles. In contrast to the results of the present
study, Sung [66] demonstrated significant changes in a modified Biering-Sørensen test after
a 4-week spinal stabilization exercise program. However, Sung’s test involved
hyperextension of the lumbar spine. Evaluation of the effect of 12 weeks specific device
training, using an identical Biering-Sørensen test as the test used in the present study,
demonstrated increased endurance time, but no significant changes in the slope of the
median frequency [36].
In accordance to the present findings, Mannion et al. [36] demonstrated no significant
differences in flexion-relaxation capacity of the back muscles between baseline
measurements and data after 12 weeks of device training.
Questionnaires
In both groups, functional disability (QBPDS) decreased after the intervention period and
further decreased at 1-year follow-up. Immediately after therapy, there was a statistically
significant between-group difference in favour of the specific exercise therapy, but at 1-year
follow-up this difference was no longer present. Some consideration should be showed to
the fact that more patients of the device exercise group (28.57%) followed other therapies
during the year following the intervention in comparison with the patients in the specific
exercise group (14.81%). This could have eliminated the between-group difference after 1
year. Lewis et al. [28] reported a mean decrease of 15.4 in QBPDS from patients receiving
8 sessions of a similar treatment to the present specific exercise therapy, but to which an
164
Specific exercise therapy versus exercise therapy on devices
information booklet (The Back Book) was added. In the present study, the mean decrease
between baseline and 1-year follow-up was 19.44 (SD 16.74) and 18.07 (SD 13.84) for the
specific exercise group and the device exercise group, respectively. This was in agreement
with the criterion that a change of at least 15 points in the QBPDS score was necessary to
be 90% confident that real change had occurred [10,13].
In accordance with the results of the present study, functional disability measured by the
Oswestry Disability Inventory (ODI) [14,40,41,44,52,66] or the Roland-Morris Disability
Questionnaire (RMDQ) [7,19,38] was shown to be significantly reduced after specific
stabilization exercise therapy. Device training showed similar results based on the RMDQ
[33-35]. In the present study, the QBPDS was preferred due to some limitations of the
ODI and the RMDQ. The ODI did not specifically score disability because a pain intensity
and a social life question were included in the questionnaire. The RMDQ was reported to
show poor reliability possibly due to the instructions which urge the patient to indicate the
disability on that specific day; this could lead to uncompleted forms if patients have not
attempted certain activity that day [10].
The time period (current pain, pain over past week/6 weeks/month/ …) in measuring
pain intensity appears to differ substantially. The time period used in the present study,
namely the average pain intensity over the past week, was shown to demonstrate best
reliability (ICC=0.88, SEM=6.59) [24]. In both groups, this pain intensity decreased
significantly after treatment, but there was no significant difference between the scores
immediately after treatment and the scores at 1-year follow-up. Similar results were
reported in lumbar stabilization training programs with 5-month [24] and 1year follow-up
[40] as well as in device exercise training with 1 year follow-up [34]. In contrast,
Kankaanpää et al. [22] reported even a further significant decrease between post-treatment
and 1-year follow-up pain intensity after device training.
In accordance with the initial pain intensity findings, the MPI-I demonstrated significantly
decreased pain severity, but also significantly improved pain interference with daily life,
perceived life control and affective distress. The affective descriptors of the Short-Form
McGill Pain Questionnaire showed similar results after specific stabilization training [24].
The baseline scores of both the MPI and the average pain intensity over the past week were
significantly different in the subjects who dropped out and the subjects who completed the
device therapy. Since both therapy interventions did not pay attention to social functioning,
165
Chapter 7
the score of the ‘social support’ subscale remained unchanged after both therapy
interventions.
Psychosocial questionnaires revealed a significant reduction in fear-avoidance (TSK) after
both active interventions. Koumantakis et al. [24] described very similar TSK baseline and
post-stabilization treatment scores to the scores obtained in the present study. The
tendency to focus excessively on pain sensations and to perceive oneself as unable to
control the intensity of pain, as measured by the PCS, was significantly decreased in both
groups. Pain catastrophizing was only described in the study of Mannion et al. [35] and
appeared not to change significantly after 12 weeks of device training. However, only a
score of 0 to 2 was used to indicate the catastrophizing strategies. To interprete treatment
changes appropriately, it is considered indispensable to use validated and reliable
questionnaires [70]. Since the TSK and PCS scores were higher in the patients who
dropped out than the patients who completed the device training, our study results may be
affected.
Though the DRAM has been used to determine changes in depression and distress in
stabilization programs [7] and device exercise training [35], the present study opted to
exclude patients with clear distress or depression symptoms. However, to be able to
evaluate these properties over time in the remaining population, the HADS was applied.
The HADS was shown to be capable of detecting minor changes in depression and anxiety
[17]. The HADS findings report significant decreased scores in the anxiety and depression
subscales as well as in the total scale. No differences were reported between both groups.
Though the present population was a specific selected population and no multidisciplinary
treatment was offered, the active treatments applied in the present study appeared to have a
positive effect on these psychological properties. In contrast, Risch et al. [53] demonstrated
no significant improvements in anxiety and depression, measured by the Mental Health
Inventory (MHI), after 10 weeks of device exercise training. Pre-treatment MHI scores
were reported high in contrast to the ‘mild disturbance’ HADS scores in the present study
[71]. These mild scores were not unexpected due to the DRAM exclusion criterion.
The SF-36 questionnaire evaluated several health-related components. The findings of the
present study showed improvements in physical functioning, social functioning and health
166
Specific exercise therapy versus exercise therapy on devices
transition in the specific exercise group, but not in the device exercise group. The findings
of the physical functioning concur with the results of the QBPDS and confirm that the
patients of the specific exercise group obtained more improved physical functioning in
daily life in comparison with the device exercise group. It appears that when active therapy
is directed to the daily needs and work complaints of the CLBP patient as applied in the
present specific therapy, the physical functioning can change effectively. The reason the
social functioning only improved in the specific exercise group, may be related to the
therapy location. Though both groups came to the same building in the university hospital,
the patients of the specific exercise therapy group were in a room with only themselves and
the musculoskeletal therapist in contrast to the patients of the device exercise therapy
group who trained in a larger room where also other patients were training on other
devices. Having seen other patients train may also have influenced the fact that they did
report smaller improvements in health transition (‘compared to one year ago, how would
you rate your health in general now’).
In accordance to the results of the pain inventories, the SF-36 subscale reporting ‘lack of
bodily pain’ showed similar improvements in both groups. General health, vitality and role
limitations due to physical problems also improved quite equally in both groups. However,
baseline data concerning general health, vitality, lack of bodily pain and mental health were
significantly lower in the patients who dropped out of the device exercise training than in
those who completed the program. Earlier research confirmed improvement of the
physical component of the SF-36 after specific stabilization training [7] and of all SF-36
subscores after device exercise training [27].
CONCLUSION
The findings of this study indicate that in a CLBP population with motor control
impairment 18 sessions of specific exercise therapy or device exercise therapy are effective
to improve pain, functional disability, psychosocial status and general health. Functional
tests indicated also increased flexion and extension strength, abdominal muscle endurance
and relative MF activity during stabilization exercises with trunk movements and seated
stabilization exercises with lower limb movements.
Between-group differences were in favour of the specific exercise therapy. More improved
physical and social functioning, less beliefs that pain was a signal for damage and increased
167
Chapter 7
relative MF activity during stabilization exercises with upper limb movements and standing
stabilization exercises with lower limb movements in the specific exercise group versus the
device exercise group indicate that specific therapy focusing on the patients’ daily needs
and work complaints is more beneficial than general muscle reconditioning.
In conclusion, both active therapy interventions are effective. Limited evidence was found
to recommend specific exercise therapy over device exercise therapy.
Acknowledgements
The authors would like to thank the doctors and the administrative staff (Kathleen and
Juri) of the Department of Physical Medicine and Orthopaedic Surgery, the Centre of
Sports Medicine and the Department of Occupational Medicine (Dr. Morthier and staff) of
the Ghent University Hospital. We are also very grateful to the therapists of the
physiotherapy department of the hospital for the practical arrangements (Sonja, Isabel and
Piet) and the therapeutic interventions (Nancy Vankeirsbilck and Patrick Lannoy). Many
thanks also to the physiotherapists of the Centre of Sports Medicine (Fabienne, Saskia,
Hilde, Mike and Benedict). To Karen Devreese and Liselot Schelfaut thanks for the
assistance in data processing.
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23. Käser L, Mannion AF, Rhyner A et al (2001) Active therapy for chronic low back pain.
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24. Koumantakis GA, Watson PJ, Oldham JA (2005) Trunk muscle stabilization training
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25. Koumantakis GA, Watson PJ, Oldham JA (2005) Supplementation of general
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26. Larivière C, Arsenault AB, Gravel D et al (2002) Evaluation of measurement strategies
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28. Lewis JS, Hewitt JS, Billington L et al (2005) A randomized clinical trial comparing two
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30. Main CJ, Wood PLR, Hollis S et al (1992) The distress and risk assessment method. A
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37. Marshall PW, Murphy BA (2003) The validity and reliability of surface EMG to assess
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Electromyogr Kinesiol 13(5):477-489
38. Moseley L (2002) Combined physiotherapy and education is efficacious for chronic low
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39. Nelson BW, O’Reilly E, Miller M et al (1995) The clinical effects of intensive, specific
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40. Niemistö L, Lahtinen-Suopanki T, Rissanen P et al (2003) A randomized trial of
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41. Niemistö L, Rissanen P, Sarna S et al (2005) Cost-effectiveness of combined
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45. O’Sullivan PB, Twomey LT, Allison GT (1998) Altered abdominal muscle recruitment
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174
GENERAL DISCUSSION
175
176
General discussion
SUMMARY AND CLINICAL IMPLICATIONS
Trunk muscle recruitment patterns during stabilization exercises in a healthy
population
Analysis of stabilization exercises in four-point kneeling (Chapter 1) and bridging
stabilization exercises (Chapter 2) showed that the relative muscle activity did not exceed
32% of maximal voluntary isometric contraction (MVIC). From a clinical point of view,
appropriate stabilization exercises, with the aim to hold and control the lumbar spine in a
neutral position, were assumed to work the trunk muscles at approximately 30% of their
maximum.1 The studies presented in this dissertation demonstrated that exercises in fourpoint kneeling and bridging exercises with control of the neutral spine position are
adequate stabilization exercises.
However, not all trunk muscles demonstrated activity levels of 30% of MVIC. In
accordance to related studies2-6, relative abdominal muscle activity of RA was low during all
bridging exercises and exercises in four-point kneeling. Considering the distal caudal
directed fibre orientation, the RA is effective in creating posterior rotation of the pelvis,
trunk flexion and producing force to counteract the hip flexor force vectors.2,6-9 Since this
were not the main directions in the present stabilization exercises, low level activity was
evident. If, in function of real reconditioning, higher relative activity levels of the RA are
needed, curl-ups can be recommended which produce relatively low activity of the oblique
abdominals.10,11 During exercises with bilateral leg movements in supine position, the RA
was also shown to respond with a large increase in activity.7 However, in clinical practice it
often occurs that the RA shows adequate coordination and strength, with only the oblique
abdominal activity that need to be adjusted.12 The relative oblique abdominal muscle
activity was in general somewhat lower during the bridging exercises in comparison with
the four-point kneeling exercises.
Though symmetric activity of the inferior fibres of the internal oblique (IO), in accordance
to its suggested segmental stabilizing function13,14, was shown during asymmetric lifting
movements15, the IO showed asymmetric activity during the asymmetric stabilization
exercises investigated in the present studies. During asymmetric exercises in four-point
kneeling, the contralateral IO demonstrated higher relative activity levels in comparison
177
with the ipsilateral IO, but during asymmetric bridging exercises, the ipsilateral IO showed
higher relative activity levels than the contralateral IO. During both types of stabilization
exercises, a hip and knee extension was present in the ipsilateral leg, but during the fourpoint kneeling exercises the contralateral hip was flexed in contrast to an extended
contralateral hip joint during the bridging exercises. The different influence of gravity in
both postures may also have contributed to the contrasting IO activation during the
asymmetric exercises. In general, during these stabilization exercises, the IO seems to cooperate with the EO in order to create a stable unit.
Analysis of the relative contribution of local to global abdominal muscles during bridging
exercises showed a very high IO/RA ratio and a variable IO/EO ratio. The IO/RA ratio
was very high due to minimal RA activity. Since during the asymmetric bridging exercise
the relative EO activity was quite symmetric and the IO showed important differences
between the ipsilateral and contralateral side as mentioned above, the ipsilateral ratio was
significantly higher than the contralateral ratio and the ratios during the symmetric bridging
exercises. The relative muscle activity and the ratio of the abdominal obliques seem to alter
depending on the task and the presumable need for stability.
The relative back muscle activity levels were similar in four-point kneeling and bridging
exercises. However, during the bridging exercises, rather symmetric back muscle activity
was found in contrast to the results of the four-point kneeling exercises.
When the hip was extended from a four-point kneeling position, a rotational moment
about the spine was expected to occur. The ipsilateral MF can cause an ipsilateral rotational
moment about the spine and the contralateral ICLT may create a moment in the opposite
direction to counter the spine moment. Appropriate co-contraction of the ipsilateral MF
and the contralateral thoracic part of the iliocostalis lumborum (ICLT) may generate
stability. This finding is contrasting to the symmetric MF activation demonstrated during
asymmetric lifting exercises15. However, during the asymmetric lifting exercises the pelvis
was more stabilized since both feet remained on the ground, in contrast to only a single
floor contact during the bridging stabilization exercises and the stabilization exercises in
four-point kneeling.
The findings concerning the relative muscle activity and the ratios of the back muscles
support the assumption that during these stabilization exercises, all back muscles contribute
in a similar way to control spine positions and movements in a healthy population.16
178
General discussion
A rehabilitation program addressing the back muscles could include both bridging and
four-point kneeling stabilization exercises. If higher activity levels of the abdominal
muscles are required, the four-point kneeling exercises seem more appropriate than the
bridging exercises.
Analysis of relative muscle activity levels and ratios of relative muscle activity during fourpoint kneeling and bridging stabilization exercises in healthy subjects indicates a
harmonious co-operation of all trunk muscles, both local and global muscles. The
investigation of ratios during the four-point kneeling exercises could have created even
more comparisons between both types of stabilization exercises. Since this analysis was not
performed, it may be considered a limitation of the first study.
Today, specific stabilization therapy is often used in primary and secondary prevention
programs of LBP. In order to assess the usefulness of specific stabilization training adapted
in primary prevention programs, evaluation of the capability to change muscle recruitment
patterns was a first step (Chapter 3). Analysis in healthy subjects demonstrated a significant
increase in local abdominal muscle activity, but the increase of local back muscle activity
was not significant after motor control training. During the symmetric bridging exercises,
the relative global RA activity significantly increased after the intervention. The global
ICLT back muscle showed not significantly decreased relative activity during all exercises.
The significantly higher relative local abdominal muscle activity and the combination of
small unsignificant increased local and decreased global relative back muscle activity after
training was responsible for the result that all post-training local/global relative muscle
activity ratios were higher (not all significantly higher) than the pre-training ratios. The
increased local/global relative muscle activity ratios during all exercises in four-point
kneeling and bridging stabilization exercises indicated that muscle recruitment patterns can
be changed in a healthy population.
Since deficient motor control was shown to be associated with low back problems17-21,
improvement of this motor control may be expected to intervene in the natural process
and perhaps prevent the onset or recurrence of LBP. However, not all participants of
primary prevention programs may benefit from this training. It seems obvious that healthy
controls and patients with appropriate motor control will not need this training and
179
perhaps need other, maybe more intensive, preventive exercises. A key issue within this
context is detecting patients with a motor control impairment.
Selecting patients with motor control deficits has been shown difficult. Several tests have
been proposed. To determine whether the local muscle system functions adequately,
assessment of the motor control of the transversus abdominis (TA) and the MF has been
described by Hodges.14,22 The assessment of motor control of TA involves evaluation of
the ability of a person to cognitively perform the skill of contraction of TA independently
from the global muscles. The parameter that is measured is the precision of the task.
Contraction of TA involves narrowing the waist and a slow and gentle inward movement
of the lower abdomen. The performance of the task is assessed in two ways: (1)
identification of signs that TA is active and (2) identification of evidence that there is no
activity of the other muscles. At the completion of the assessment, the clinical outcome is
judged from the precision of the independent activation of TA. The test of MF evaluates
the ability to cognitively perform the skill of contraction of MF, particularly the deep fibres,
independently of the superficial fibres. It is also supposed to be useful to palpate the
relaxed muscle, because changes in muscle consistency may be present. From a prone
position, the test of MF activation involves an isometric “swelling” contraction of the
muscle. The outcome of the assessment of the local muscles is judged on the interpretation
of the observation, palpation and if possible, EMG findings. Ultrasound may also provide a
more accurate indication of activation of TA and MF. 14,23
It may be assumed that when healthy people are not able to perform adequately these
motor control tasks, specific stabilization training might be advised in prevention
programs. However, other clinicians have suggested a broader evaluation method including
different physical tests to determine motor control impairment.21
Trunk muscle recruitment patterns in a healthy population during exercises on
specifically designed lumbar training devices
In chapters 4 and 5, it was demonstrated that during low-load exercises on training devices
(at 30% of mean maximal torque), activity levels of more than 60% of MVIC were
obtained by the MF and the longissimus thoracis (LT) and by the MF, LT, ICLT, latissimus
dorsi (LD) and EO during extension and rotation, respectively. Activity levels of at least
180
General discussion
60% of MVIC are generally accepted for basic strength training purposes.24 The ICLL and
ICLT during low-load extension exercises and the MF, ICLT, LD and abdominal obliques
during low-load rotation exercises showed relative activity levels between 30 and 60% of
MVIC. All muscles during the flexion exercises, the abdominal muscles during the
extension exercises and the RA during the rotation exercises showed relative activity levels
of less than 25% of MVIC.
Mindful of these findings, the movement direction trained during low-load exercises can be
selected based on the preferred muscles to be trained at certain intensities as well as on the
functional need of the subject in daily life conditions.
Dynamic exercises on training devices at 30% of maximal mean torque (MMT) appeared to
reach higher relative activity levels than stabilization exercises. Caution should however be
taken in comparing both exercise types. The analyzed time periods during the stabilization
exercises were static, in contrast to dynamic movements during the exercises on devices.
Analysis of EMG signals during dynamic movements may ignore the differences in lengthforce relationships and consequently may create higher activity levels. In a dynamic
contraction, various mechanical, physiological, anatomical, and electrical modifications
occur throughout the contraction that affect, in substantial ways, the relationship between
signal amplitude and muscle force.25
The effect of increasing resistance during exercises on specifically designed lumbar
training devices, evaluated in a healthy population
In general, increasing resistance from 30% MMT to 50% MMT and 70% MMT created
significantly increased relative activity of all back muscles during the extension exercises
and of all abdominal exercises during the flexion exercises. During rotation exercises,
increased resistance from 50% to 70% MMT created consistently higher relative activity
levels in all trunk muscles. However, the relevance of increasing resistance on specifically
designed training devices should be questioned. Since in general high relative activity levels
were obtained even during low-load 30% MMT exercises, increasing the resistance on this
kind of training devices may be questioned and may not always be beneficial. Applying high
resistance levels may be appropriate for sport training situations, but may not always be
181
needed in rehabilitation context. Furthermore, especially during the first period of
rehabilitation, high resistance may be detrimental since higher resistance levels may be
associated with high loads on the spine.
It seems appropriate to advice clinicians to evaluate the needs of each specific subject in
order to try to accurately match the training and the subject rather than completely relying
on the system to progress the training scheme.
The effectiveness of specific exercise therapy versus trunk muscle reconditioning
on devices in a chronic LBP population
The main purpose in the rehabilitation of CLBP patients is functional improvement or
restoration and if possible, pain relief to increase the general well-being. The results of the
randomised clinical trial demonstrated improvement of all three components after both
exercise interventions. In comparison to the device exercise therapy group, functional
disability and physical and social functioning improved more in the specific exercise
therapy group. The patients of the specific therapy also reported higher self-rated health
change compared to one year ago.
The Quebec Back Pain Disability Scale (QBPDS), measuring functional disability, as well as
the subscale physical functioning of the SF-36 showed greater improvement in the specific
exercise group in comparison with the device exercise group. Through 1-year follow-up,
the QBPDS score further significantly decreased, but the between-group difference
disappeared. Due to the results at 1-year follow-up and since in both therapy groups
clinical significant 15-points increases were found concerning the QBPDS, caution is
warranted in extolling the effect of the specific exercise therapy. The QBPDS can be
completed in 5 minutes by the patient and is scored in 1 minute by the therapist.26
Consequently, application in clinical practice is easy and useful.
The pain intensity scale and a subscale of the first part of the Multidimensional Pain
Inventory demonstrated decreased pain intensity in both groups. Similar outcome obtained
by different questionnaires as reported concerning pain and physical functioning, confirms
the validity of the scores. Nor immediately after the intervention nor at 1-year follow-up a
182
General discussion
between-group difference was present. Pain intensity at 1-year follow-up was not
significantly different from the scores immediately after treatment, but remained smaller
than before the intervention.
General health was only determined before and immediately after exercise therapy.
Improvement was shown in both groups without a between-group difference. General
well-being encloses both physical and emotional components and consequently the whole
patient.
Though positively affecting physical functioning, pain and general well-being are the most
important issues for patients, the effect on functional outcome measures and psycho-social
characteristics is assumed to be important to avoid dependence on the health care system
at long-term.
Several psycho-social patient characteristics were improved after both therapy
interventions, but no differences were observed between both groups. Though patients
with severe distress or depression were excluded from the study, it appeared still possible
to affect psycho-social outcome. As often described, pain and certainly chronic and
recurrent pain is not only a matter of physical “dysfunction”, but the whole person is
involved.27-29 Without specific cognitive or psychological therapy, exercises appeared to be
capable of improving the psycho-social functioning of the population investigated in the
present randomized clinical trial. The present population showed mild to moderate
kinesiophobia, anxiety, distress and catastrophizing baseline scores. The patients excluded
from the present study, as well as patients consulting other departments than the physical
medicine and orthopaedic surgery department of the hospital, for example the chronic pain
clinic may need more intensive multidisciplinary rehabilitation.
Concerning the functional measurements, it was shown that 18 treatment sessions of
specific exercise therapy or device exercise therapy are capable of improving trunk strength
torque, relative MF activity, abdominal endurance capacity of chronic and recurrent LBP
patients with a motor control impairment.
183
The functional clinical test battery evaluated muscle activity during coordination,
stabilization, flexion-relaxation, endurance and strength exercises, as well as proprioception
and postural control.
Although proprioception30-35 and postural control32,36-40 were shown to be dysfunctional in
CLBP patients, only one study evaluated the effect of LBP rehabilitation on postural
control41 and no LBP population studies were reported on proprioception. Kuukkanen et
al.41 concluded that in subacute LBP patients specific exercise programs may be required in
order to enhance balance performance. Their three-month home training program
increased sway velocity in standing.
The results of the present randomized clinical trial demonstrated no significant changes in
proprioception and postural control due to any intervention. It may be difficult to
influence these parameters which could be a reason why these characteristics were scarcely
investigated in the past. The measurement methods, although similar to the ones used to
demonstrate differences between healthy subjects and LBP patients30,36, may not be
appropriate and sensitive enough to detect smaller changes caused by therapy. Repeatability
and reproducibility of these measurements appeared to be good in a healthy population
(Chapter 6), but was not yet evaluated in a LBP population.
Analysis of relative muscle activity showed a significant increase of the relative MF activity
during all stabilization exercises (with upper and lower limb and trunk movements in sitting
and standing) and significant increased relative IO activity during stabilization exercises
with upper limb movements in standing. However, during the seated stabilization exercises
with lower limb movements and during the stabilization exercises with upper limb
movements, both in sitting and standing, the relative MF activity only increased in the
specific exercise group and not in the device exercise group. Since in the specific exercise
therapy attention was paid to local muscle co-contraction in various postures and during
several exercises, benefit for the specific exercise outcome could be expected. This benefit
was however limited, since in several exercises the relative MF activity of the device
exercise group also increased. Muscle activity analysis in healthy subjects during bridging
stabilization exercises and stabilization exercises in four-point kneeling, as well as during
rotation, extension and flexion exercises on devices, presented in chapters 1 to 5, showed
high relative activity levels for MF during all exercises. The MF could be suggested a
muscle that is susceptible for various kinds of exercise therapy. If MF would be very
184
General discussion
susceptible to any kind of exercise, automatic recovery after resolution of acute, firstepisode LBP may be expected. However, this was contradicted by Hides et al.42
A possible reason for the overall high relative MF activity may be related to the spine
posture. Despite the different nature of the exercises, the similarity between all tasks was
that the criterion to start the exercises was a neutral spine position, determined by the
therapist. This emphasizes the idea that the spine position is crucial and that it may be
more important to control the neutral spine position than to give specific muscle
contraction instruction. Since trunk muscle evaluation in chapters 1 to 5 occurred in
healthy subjects, future research in patients is needed to confirm this finding.
Concerning the high relative MF activity during the device exercises, it needs to be
remarked that the Tergumed devices use controlled movements via constant biofeedback
on a computer display in front of the patient. In this way, not only strength, but also
muscle coordination is expected to be trained. Other devices without specific performance
instructions or biofeedback may generate different muscle training and different general
rehabilitation effects.
Only minimal effect was created on the relative activity of the local abdominal muscle IO.
In contrast to the results of the randomized clinical trial in a specific chronic and recurrent
LBP population, evaluation of a short training program in healthy subjects (chapter 3)
showed a clear effect on the relative local abdominal activity and no significant differences
concerning the local back muscle. The difference in results of both studies may be related
to the different population. However, other differences between both interventions were
also present. In contrast to a rather strict stepwise program applied in the healthy
population, a more global program including minimal manual therapy was used to
rehabilitate the chronic and recurrent LBP patients. The intervention period was also of
more extensive duration in the pain population than in the healthy subjects. In addition, the
exercises to test muscle recruitment that were applied during the pre and post intervention
test sessions were different in both populations. In the healthy population, stabilization test
exercises in four-point kneeling and bridging stabilization test exercises were used. In
contrast, in the chronic and recurrent LBP population, easier stabilization test exercises in
sitting and standing were adapted. Consequently, adequate comparison between both
studies is not possible. Additional research in healthy subjects may facilitate comparison
and clarify potential differences.
185
The endurance capacity of the abdominal muscles increased in both patient exercise
groups, as well as the flexion and extension peak torque. Although the specific exercise
training not aimed at strength training, but rather at functional restoration, the therapy
appeared to increase both abdominal and back muscle strength and abdominal muscle
endurance. Lower intensity exercises, encouraged to execute daily, seem capable of
increasing basic muscle characteristics which may have a positive influence on long-term
outcome. Functional disability further decreased throughout 1-year follow-up, but since
strength and endurance were not re-evaluated after 1 year, it is not possible to determine
the impact of strength and endurance on the long-term functional improvement. Though
optimal strength training was recommended to be performed three times a week43 and the
frequency of the device exercise training was only twice a week during the first 6 weeks and
once a week during the following 6 weeks, significant post-intervention improvements of
abdominal and back muscle strength were present. Literature describes that many chronic
low back pain patients have been advised to continuously decrease their activity level and
to let pain guide their activity level. Such patients become conditioned to avoid pain, which
may cause general deconditioning.44 This kind of population may demonstrate strength
adaptations more easily.
The back muscles demonstrated increased strength and the MF showed increased relative
activity during stabilization exercises, but the back muscle endurance capacity was not
influenced. Such variety in results should motivate clinicians as well as researchers to apply
different aspects in clinical evaluation. Consequently, the need for extensive functional
evaluation including different muscle characteristics is emphasized in order to comprehend
the working mechanisms of rehabilitation programs.
Both active therapy interventions affected the abdominal and back muscles in a different
way. In contrast to the coordination and strength changes of the back muscles, the
abdominal muscles demonstrated improved endurance and strength.
The results of the randomized clinical trial in chronic and recurrent LBP patients with
motor control impairment showed that 18 exercise treatment sessions are capable of
improving almost all subjective and some objective outcome measures. Though the few
between-group differences concerning relative MF activity during stabilization exercises,
186
General discussion
functional disability and physical and social functioning are all in favour of specific exercise
therapy, it seems overstated to claim that this intervention is more effective than device
exercise therapy in this population.
FUTURE DIRECTIONS
In the first and second part of the present dissertation, the muscle activity during
stabilization exercises and exercises on training devices was investigated in healthy subjects.
In order to obtain more insight in the performance of patients during this kind of exercises,
future research may direct at different specific chronic and recurrent LBP populations.
Application of the same test protocols would allow appropriate comparison between
patients and healthy controls.
The functional clinical test battery discussed in the third part of the present dissertation
was rather extensive. To limit time expenses, reconsideration of the obtained results could
allow omitting certain tests. Based on the findings of the randomized clinical trial, the
coordination exercises may be left out. Since the stabilization exercises displayed rather
similar results in sitting and standing, but seemed somewhat more discriminative in
standing, the seated stabilization exercises could be removed. Though no changes were
present in the postural control and proprioception parameters, currently we suggest
preserving these tests in order to maintain all components of functional stability.
From a clinical point of view, analysis of correlations between tests of a standard clinical
examination and tests of the clinical test battery seems very useful. Evaluation using the
clinical functional test battery on the field is possible, but requires much equipment and
trained investigators. Future research identifying clinical useful, easily applicable, relevant,
reliable and valid tests will be very challenging. In the present dissertation, we were able to
demonstrate that evaluation of the modified Biering-Sørensen test to determine the back
muscle endurance capacity displays good reproducible and repeatable measurements using
a stopwatch to obtain the test duration. Earlier research reported that this test can
discriminate between subjects with and without nonspecific LBP.45
187
In the randomized clinical trial in the present dissertation, patients were randomly allocated
to a therapy intervention, irrespective of the results of the functional clinical test battery.
Currently, a normative database is available for the functional clinical test battery.
Comparison of the test results of each patient with the normative database demonstrates
the exercises during which the patient performs worse than the average healthy population.
Consequently, on the one hand directing the patient to motor control training and specific
hands-on therapy may be indicated when low scores are obtained during coordination,
stabilization and proprioception exercises. On the other hand, when mainly strength and
endurance appear deficient, general trunk muscle reconditioning may be advised.
Evaluation of the effectiveness of therapy assignement based on the results of the
functional clinical test battery in the rehabilitation of a subgroup of chronic and recurrent
LBP patients could be addressed in future research.
GENERAL CONCLUSIONS
The aims in the present dissertation were to analyse muscle recruitment patterns during
exercises which are frequently used in clinical practice and to compare the effects of the
two most popular rehabilitation strategies in CLBP today: specific exercise therapy and
exercise therapy on specifically designed devices.
In stabilization exercises in four-point kneeling and in bridging stabilization exercises, hip
and trunk muscles, of the so-called local as well as the global muscle system, seem to work
together in a harmonious way.
Muscle recruitment patterns can be changed in healthy subjects by means of a training
program that focuses on motor control.
Increasing resistance from 30% to 50% and 70% MMT during seated axial rotation in a
Tergumed training device consistently create higher relative activity levels in all trunk
muscles. During seated extension and flexion exercises, the relative activity of all back
muscles during the extension exercises and the relative activity of all abdominal muscles
during the flexion exercises increase significantly.
188
General discussion
To train strength (>60% of MVIC), low device intensities (30% and 50% MMT) appear
sufficient to affect the back muscles, but for the abdominal obliques higher resistance (70%
MMT) seem required. In the vulnerable spine undergoing rehabilitation, training at 30%
MMT may be sufficient.
In a chronic and recurrent LBP population with motor control impairment 18 sessions of
specific exercise therapy or device exercise therapy are effective to improve pain, functional
disability, psychosocial status and general health. Functional tests indicate also increased
flexion and extension strength, abdominal muscle endurance and relative MF activity
during stabilization exercises with trunk movements and seated stabilization exercises with
lower limb movements. Limited evidence is found to recommend specific exercise therapy
over device exercise therapy.
The main purpose of the present dissertation was to make a valuable contribution to the
clinical practice of physiotherapy. The presentation of the muscle activity levels during
frequently used stabilization and device exercises and the results of the randomized clinical
trial in chronic and recurrent LBP patients will hopefully assist the clinicians in selecting
adequate rehabilitation programs in patients.
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NEDERLANDSTALIGE SAMENVATTING
193
194
Nederlandstalige samenvatting
NEDERLANDSTALIGE SAMENVATTING
In 2001 bleek uit een enquête dat 41.8% van de Belgen tijdens de afgelopen 6 maanden
geconfronteerd werd met lage rugpijn gedurende één of meerdere dagen. Lage rugklachten
blijken een grote impact te hebben op het fysiek functioneren, het professionele leven en
op de gezondheidszorg. Om de pijn en functionele beperkingen en eveneens de hoge
socio-economische
kosten
aan
banden
te
leggen,
worden
verscheidene
revalidatiestrategieën voorgesteld. Recente reviews die de effectiviteit van oefentherapie in
chronische lage rug patiënten evalueerden, toonden aan dat individueel gerichte
spierversterkende en stabiliserende oefentherapie de pijn kan verminderen en het
functioneren van de patiënt kan verbeteren. Er is echter nog onvoldoende duidelijkheid
betreffende de effecten op lange termijn.
Binnen de actieve aanpak zijn momenteel in België, maar ook internationaal, twee grote
tendensen waar te nemen. Enerzijds wordt getracht om na grondig klinisch onderzoek zo
specifiek mogelijk in te spelen op de klachten van de patiënt door hands-on en sterk
individueel begeleide oefentherapie gericht op de dagelijkse activiteiten en werksituatie van
de patiënt. Binnen deze individueel begeleide aanpak wordt vaak specifieke
stabilisatietraining toegepast. Anderzijds wordt geïnvesteerd in dure machines zodat
patiënten zelfstandig kunnen trainen volgens individueel geprogrammeerde oefenschema’s
op specifiek ontworpen lumbale trainingstoestellen.
Om de werking van deze revalidatieprogramma’s goed te kunnen begrijpen en
interpreteren, leek het in eerste instantie noodzakelijk om een idee te hebben van de
spierwerking die optreedt tijdens de uitvoering van stabilisatieoefeningen enerzijds (deel 1
van deze thesis) en oefeningen op specifiek ontworpen toestellen anderzijds (deel 2 van
deze thesis).
De geselecteerde stabilisatieoefeningen waren oefeningen in handen- en knieënstand met
arm- en beenbewegingen (hoofdstuk 1) en oefeningen in ruglig waarbij het bekken opgetild
werd (hoofdstuk 2). De resultaten van deze onderzoeken toonden aan dat de rompspieren
een activiteit leverden van circa 30% van de maximale vrijwillige isometrische contractie
(MVIC). Dit activiteitsniveau wordt verondersteld optimaal te zijn voor coördinatie en
stabilisatie doeleinden. Alle romp- en heupspieren blijken harmonisch samen te werken om
195
de controle over de neutrale lage rugpositie te behouden tijdens deze stabilisatieoefeningen.
Tijdens de oefeningen waarbij het bekken getild werd vanuit ruglig vertoonden de
rugspieren een hogere activiteit ten opzichte van de buikspieren. Tijdens beide types
oefeningen was de activiteit van de rechte buikspieren minimaal.
In hoofdstuk 3 was het de bedoeling om na te gaan of specifieke stabilisatietraining zinvol
zou kunnen zijn in primaire preventieprogramma’s. Een interventieperiode van 3 maanden
bestaande
uit
8
trainingsessies
toonde
aan
dat
het
mogelijk
is
om
rompspierrecruteringspatronen te wijzigen bij een gezonde populatie. Bijgevolg lijkt
specifieke stabilisatietraining nuttig te kunnen zijn in primaire preventie, indien klinisch
onderzoek aangeeft dat de spiercontrole niet optimaal is. Verder prospectief onderzoek is
echter nodig om deze veronderstelling te bevestigen.
De oefeningen op de specifieke lumbale trainingstoestellen (Tergumed) werden uitgevoerd
in zit. Bij dynamische oefeningen aan een lage weerstand (30% van het gemiddelde
maximale krachtmoment (GMK)), bleek bij gezonde proefpersonen tijdens verschillende
oefeningen reeds een behoorlijk hoge spieractiviteit aanwezig te zijn (hoofdstuk 4 en 5).
Sommige rugspieren (lumbale m. multifidus en m. longissimus thoracis) vertoonden tijdens
rotatie- en extensiebewegingen aan deze lage weerstand reeds een relatieve spieractiviteit
van ongeveer 60% van MVIC. Dit niveau van spieractiviteit wordt algemeen beschouwd als
het niveau nodig voor spierkrachttraining. De buikspieren vertoonden globaal een lagere
activiteit tijdens de flexie- en extensieoefeningen aan lage weerstand, maar tijdens de
rotatiebewegingen aan lage weerstand (30% GMK) vertoonde enerzijds de m. obliquus
internus abdominis een relatieve activiteit tussen de 30 en 60% van MVIC en anderzijds de
m. obliquus externus abdominis een activiteit van 60% van MVIC.
Aangezien reeds verscheidene rompspieren een relatief hoge activiteit blijken te vertonen
tijdens een oefening tegen een weerstand van 30% GMK, kan men zich afvragen of het
noodzakelijk en opportuun is om te trainen aan hogere intensiteiten. Hogere intensiteiten
lijken bij patiënten, zeker in de initiële trainingsfase, niet meteen noodzakelijk. Directe
extrapolatie van deze onderzoeksresultaten bij een gezonde populatie naar een
patiëntenpopulatie is misschien echter niet geoorloofd. Verder onderzoek bij specifieke
subgroepen van chronische lage rugpatiënten zou een beter inzicht kunnen verschaffen.
196
Nederlandstalige samenvatting
In het derde deel van deze thesis werd een klinisch gerandomiseerd onderzoek uitgevoerd
waarbij de effectiviteit van de beide actieve therapievormen werd geëvalueerd.
Bij 78 patiënten met aspecifieke chronische lage rugpijn met een motor controle disfunctie
werd de effectiviteit van specifieke oefentherapie versus rompspierreconditionering op
lumbale trainingstoestellen onderzocht (hoofdstuk 7). De therapie omvatte 12 weken met een
frequentie van 2 oefensessies per week gedurende de eerste 6 weken en 1 per week
gedurende de volgende 6 weken.
De specifieke oefentherapie bestond voor 90% uit motor controle stabilisatietraining en
voor 10% uit manuele therapie (mobilisatie en weke delen technieken) en educatie. Het
behandelproces bevatte een graduele progressie door verandering van onder andere
posturale belasting, vermindering van aandacht en van snelheid met het uiteindelijk doel
om functionele verbetering te bekomen bij de patiënt. Dagelijkse thuisoefeningen werden
aangemoedigd.
Voor de globale rompspierreconditionering werd beroep gedaan op 4 lumbale Tergumed
trainingstoestellen. Het oefenprogramma was gebaseerd op de individuele resultaten van de
patiënt van isometrische kracht en mobiliteit zoals gemeten tijdens de eerste en tiende
behandelsessie. Het oefenprogramma startte met minimaal 4 isometrische trainingssessies
gevolgd door dynamische oefensessies. Tijdens de uitvoering van de oefeningen ontving de
patiënt continu feedback via een te volgen sinusoïdale curve op een beeldscherm. Elke
sessie werd voorafgegaan door 10 minuten opwarming op een hometrainer en beëindigd
door de uitvoering van 4 verschillende stretchingsoefeningen. Ter evaluatie van de
effectiviteit van de therapie werden verschillende vragenlijsten gehanteerd en werd een
functionele testbatterij doorlopen. De functionele testbatterij evalueerde verschillende
componenten van functionele stabiliteit, namelijk proprioceptie, posturale controle en
spierwerking. Wat de spierwerking betrof, werden diverse oefeningen uitgevoerd
(coördinatie-, stabilisatie-, kracht- en uithoudingsoefeningen, evenals een volledige
rompflexieoefening om het relaxatievermogen van de rugspieren te beoordelen). Deze
testbatterij bleek een betrouwbaar meetinstrument (hoofdstuk 6).
De resultaten van dit effectiviteitsonderzoek toonden aan dat zowel pijn, functionele
beperking, algemene gezondheid, psychosociale aspecten als functionele parameters
positief beïnvloed werden. Een licht voordeel van de specifieke therapie ten opzichte van
de oefentherapie op toestellen werd vastgesteld. Aangezien dit voordeel betreffende de
functionele beperking echter verdwenen was bij de 1-jaar follow-up en de andere metingen
197
niet herhaald werden na 1 jaar, dient dit voordeel met de nodige voorzichtigheid
geïnterpreteerd worden.
De resultaten zijn tevens enkel geldig voor de specifieke subpopulatie van chronische lage
rugpatiënten die geselecteerd werd, namelijk patiënten met aspecifieke klachten zonder
radiculaire symptomen en zonder eerdere rugchirurgie waarbij een motor controle
disfunctie werd vastgesteld.
Niettegenstaande de onderzoeken naar de spierwerking plaatsvonden bij een gezonde
populatie blijken de resultaten gecorreleerd te kunnen worden aan de resultaten van de
patiëntenstudie. Tijdens de onderzochte stabilisatieoefeningen, evenals de geanalyseerde
oefeningen op de toestellen bleek steeds een vrij hoge relatieve activiteit van de lumbale m.
multifidus aanwezig te zijn. Deze spier bleek tijdens de patiëntenstudie als enige een
significante activiteitstoename tijdens de stabilisatieoefeningen na therapie te vertonen.
Wat betreft de oefeningen op de lumbale trainingstoestellen, dient het specifieke karakter
van de toestellen vermeld te worden. Doordat de Tergumed toestellen een biofeedback
systeem hanteren waarbij de snelheid van de bewegingen, evenals de ROM continu
gecontroleerd worden, is het misschien niet geoorloofd de resultaten van deze therapie te
extrapoleren naar trainingsprogramma’s op andere toestellen waarbij minder of geen
controle aanwezig is.
Met deze thesis werd getracht een waardevolle bijdrage te leveren aan de klinische
kinesitherapeutische praktijk door een beter inzicht in vaak gebruikte oefeningen te
verschaffen, evenals door de effectiviteit van actieve therapievormen te vergelijken in een
specifieke chronische lage rugpopulatie.
198
199
Things should be made as simple as possible, but not any simpler.
(Albert Einstein)
200