Download Isokinetics part 1.pps - North Wales Sports Clinic Ltd

North Wales Sports Clinic Ltd
Isokinetics part 1
Russ Davison MCSP HPC - July 2014
Why Use Isokinetics
Isokinetic motion is unique in that the force developed by the subject is equally
matched by the machine.
Isokinetics has been shown to effective in many situations.
Knee:
Genêt et al (2008) found isokinetic strength to be related to disability,
impairment and satisfaction following knee replacement.
All the following authors used isokinetic strength as the gold standard measure
following arthroscopy.
Ericsson YB et al (2006), Koutras G, Pappas E, Terzidis IP (2009),
Woods GW, Elkousy HA, O'Connor DP (2006), Miura K et al. (2004)
Fabiś J (2007)
found isokinetic training increased muscular function following ACL
reconstruction.
In fact in ACL rehabilitation –
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Asagumo H et al (2007)
Moisala AS et al (2007)
Harilainen A, Linko E, Sandelin J (2006)
Goradia VK, Grana WA, Pearson SE (2006)
Lee S et al. (2004)
And literally hundreds of others all used isokinetic strength testing as a gold
standard following ACL reconstruction.
Isokinetics testing of strength is also extensively used in rehabilitation of the ACL
deficient knee (a growing trend world wide) as demonstrated as early as 2004 by
Patel RR, et al.
Shoulder:
Ellenbecker TS, Davies GJ. (2000) this was a meta analysis of Isokinetics in the
shoulder. This was part of their conclusion.
‘Isokinetic training and testing is an important part of the comprehensive
evaluation and rehabilitation of the patient with a shoulder injury. Research has
demonstrated its efficacy in training and in providing clinically relevant
information regarding muscular performance’.
Fabis J (2007) used isokinetic evaluation pre and post arthroscopy of the
shoulder with nerve entrapment.
Signorile JF, (2005) showed Isokinetics could predict and improve tennis
performance.
Bellumore Y, Mansat M, Assoun J. (1994) stated that muscle performance was
vital to shoulder head stability before and after rotator cuff rupture and repair
(they used and suggested Isokinetics to achieve this).
Bayder M et al. (2009) said isokinetic rehab of full thickness rotator cuff tears
demonstrated 'satisfactory' results without the need for surgery.
Elbow:
Peeters T et al. (2009)
Used Isokinetics as the assessment for strength following biceps tendon reattachment.
Pienimäki TT, Siira PT, Vanharanta H. (2002)
Showed Isokinetic strength related to (and could reduce) elbow tendon
dysfunction (assess and reduce tennis elbow).
Wrist:
Croisier JL et al (2007)
Used Isokinetics to resolve wrist tendonopathies.
Hip:
Boling MC, Padua DA, Alexander-Creighton R (2009) and Nakagawa TH (2008)
Both found hip strength to be an important component in some knee
problems.
ML, Zhang Y, Rogers MW (2008)
Found hip strength to be vital in the prediction of falls in the elderly.
Silder A, Heiderscheit B, Thelen DG (2008)
Found hip strength became more vital as you aged and could compensate for
poor ankle strength.
Bhave A, (2007) and Rossi MD et al. (2006)
Looked at isokinetic strength following hip replacement.
Ankle:
Gribble PA, Robinson RH. (2009) and Sekir U. Et al. (2008)
Found ankle strength to be vital in stability around the joint.
Hartmann A et al. (2008)
Found ankle strength to influence mobility in elderly populations.
Ozçaldiran B, Durmaz B. (2008)
Said isokinetic evaluation and strengthening was a vital tool when working with
sprint athletes and swimmers for both injury prevention and performance.
Hohendorff B et al. (2008) Gigante A et al. (2008)
Used Isokinetics as the gold standard measure of strength following Achilles
Tendon repair.
Sandrey MA, Kent TE. (2008) and Fox A et al. (2008)
Found the ankle became more unstable as the muscles became weaker.
Mahieu NN et al. (2008)
Showed the properties of the Achilles Tendon could be influenced by isokinetic
training.
What is Isokinetics
The word isokinetic is most commonly used in sports science and medicine.
Isokinetic (n) is a term used to describe a type of movement or exercise.
Isokinetics Definition:
Translated literally isokinetic means movement at a constant speed.
The key to isokinetic movement or exercise is:
That the speed of the motion is always kept the same even as the resistance alters.
Isokinetic - Isotonic
Isotonic movement is the most common type of movement we human beings
perform:
Isokinetic movement is actually the opposite of isotonic movement which is
probably the easiest way to think of it.
Isotonic movement:
Every day, we perform isotonic movements.
For Example: we pick up a fixed weight, (a briefcase) or basically anything that
has weight.
The weight of the briefcase is fixed but we decide how fast to lift it.
We can lift it slow, fast, or anywhere in between.
The key to this type of movement is: We decide how fast it goes but the weight
(resistance) remains constant.
Isokinetic movement:
In isokinetic movements the situation is reversed now we tell an isokinetic machine
(the dynamometer) to move only at a certain speed (normally described in degrees per
second).
The machine will then vary it's resistance against the subject in order to maintain that
set speed.
If we push against the machine hard it will give back a lot of resistance to maintain the
speed that was set.
If we push or pull softly the machine reduces the weight to maintain the set speed.
Most medical isokinetic machines are top of the range.
They use a powerful motor to provide the isokinetic resistance to the force applied and
then use a computer to keep the motion smooth, provide the acceleration and to
record the results.
The clinics machine is the very latest available having both a digital motor and a digital
servo making it extremely smooth in its operation.
Advantages - Disadvantages
Advantages:
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Maximal loading throughout whole range of motion.
Objective, results are reproducible and easily quantifiable.
Muscles easily isolated.
Safest form of exercise.
Few contraindications.
Disadvantages:
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Time consuming.
Requires a lot of training and skill to use.
Costly.
Results can be difficult to compare between machines.
What is Isotonic?
Isotonic (n) literally means equal tension.
In exercise science isotonic contraction is a contraction in which the tension remains
constant as the muscle shortens or lengthens.
Isotonic is a fixed resistance variable speed movement.
Although 'isotonic' is the term used most frequently to describe fixed resistance
variable speed exercise, ‘Isoinertial' is a more accurate description of this type of
movement .
(Abernethy et al. 1995)
In reality it takes a very complicated piece of equipment, like an active dynamometer,
to create pure isotonic exercise.
People generally think of isotonic exercise as that seen in the gymnasium.
The simplest example of this is where a dumbbell is lifted from the ground and used
to perform an exercise.
The tension generated by the dumbbell is now the constant, or in other words if you
pick up a 2 kilo dumbbell it weighs 2 kilos whatever you do with it.
The elaborate cam systems seen on most modern weight training equipment allow for
a more isotonic movement to be performed.
The key to isotonic exercise is that: although the weight is constant the speed of
movement associated with the exercise is variable.
Think again of the dumbbell curl. The dumbbell will always weigh 2 kilos but you can
decide how quickly to move it.
Although the reliability of isotonic exercise is generally good, controlling the inertial
forces that develop with different lifting techniques make it inappropriate for the study
of musculoskeletal performance in humans.
(Sapega 1990).
This method of testing should be limited to active dynamometers.
Even then isotonic movement should only be used for the assessment of speed
production at a given resistance.
Exercise programs have been proven to be most effective when the movements
performed match those experienced most frequently by the person in question.
(Morrissey, Harman and Johnson 1995).
For humans the closest form of exercise to normal movement is isotonic.
So it would not be surprising to find that isotonic exercise increases
muscle strength at double the speed of isometric exercise in the
untrained population according to:
Connelly and Vandervoort (1995).
Advantages - Disadvantages
Advantages:
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Functional.
Easy to monitor.
Convenient - Minimal equipment needed.
Best strength and Endurance enhancements.
Disadvantages:
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Maximum loading only at specific angles.
Momentum key factor.
Synergists either over or under trained.
Unsafe for joints - Highest likelihood of injuries.
Gives delayed onset muscle soreness.
Many Contraindications.
What is Isometric?
The term isometric (n) comes from the Greek "ios" which means the same, and
"metric" which means distance.
Combined together they make a static contraction where there is no perceivable
motion.
There are two types of isometric resistance:-
 An immovable force (overcoming isometric)
 An opposing resistance (yielding isometric) which is what Isokinetic machines
produce.
Isometric is variable effort against an immovable force.
Isometric is used to describe both a type of contraction and a type of exercise!
Isometric contraction and isometric exercise are again two interchangeable terms.
To elaborate on this it seems people describe an isometric contraction as performing
isometric exercise.
Hislop and Perrine (1967) described isometric exercise as muscular contractions
against a load which is fixed or immovable or is simply too much to overcome.
Although it has been shown that strength gains are possible from isometric
contraction these strength gains are very minimal and almost all studies have
shown that the gains in pure muscular strength are only at the specific angle at
which the exercise is performed. (NASA 2004)
Hence, to make isometric exercise effective at increasing functional strength it
must be repeated at many different joint angles.
Isometric improvements have also been shown to be rate specific (Morrissey,
Harman and Johnson 1995), this means that isometric strength gains can be
best utilized only at particular speeds.
These improvements are seen mostly in slower movements which are not
functional and of little use to people wishing to return to any kind of physical
activity.
Why use isometric training?
Most people in the fitness industry today - train dynamically - and
generally avoid isometric training.
Recent research suggests that it can be a very effective training
method and, if done across a range of angles, it does not necessarily
have to limit strength gains to specific ranges of motion.
Strength training: Isometric training at a range of joint angles versus
dynamic training, by Folland, Hawker, Leach, Little and Jones, Journal
of Sports Sciences (2005)
Large increases in strength
through isometric training
A number of researchers have observed that very large and rapid
increases in strength occur as a result of isometric training.
Lindh (1979) noted an increase of 30% in 5 weeks
Young (1985) noted an increase of 40% in 8 weeks
Thepaut- Mathieu (1988) reported an increase of 25 –
54% in 5 weeks
Weir (1995) found that strength increased by 27% in 6
weeks
Compared to concentric-only or eccentric-only training, these kind of
results look pretty good.
The chart below shows a study by Jones (1987), in which some of the
other dynamic options were compared with isometric training:
Researchers have usually found that training at a specific joint angle (train
isometrically) leads to large strength gains at that angle but not at all other
angles.
In the following chart , taken from Bandy (1993), we can see how training at
different angles leads to angle-specific strength gains.
You can see that when training at 30-degrees, for example, the greatest
increases are in the 15-45 degree range.
While when training at 90 degrees, the greatest increases are in the 75-90
range.
Researchers have generally concluded that with dynamic training
(eccentric-only or concentric-only), strength increases throughout the
whole range of motion are smaller but more evenly distributed.
How does the research stack up?
Researchers found that both isometric and dynamic strength training
significantly increased the isometric strength of both legs at a range of
angles.
However, the gains in isometric strength were greater in the
isometrically–trained leg than in the dynamically-trained leg at all the
angles measured.
They also found that the relative improvements in isometric strength
were not equal at all joint angles for both isometrically-trained and
dynamically-trained legs.
However, there was a strong pattern observed for both types of training.
The chart below shows how both types of training appeared to lead to
similar strength gains at the different angles tested:
The chart below shows how both types of training appeared to lead to
similar strength gains at the different angles tested:
Both types of training significantly increased the isokinetic strength at a
range of speeds.
The improvements in isokinetic strength were similar with both training
programs.
The Researchers conclusions
The researchers drew the following conclusions:
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Both programs led to significant improvements in both
isometric and isokinetic strength.
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Both programs led to similar gains in isokinetic strength.
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Isometric training at four joint angles led to significantly greater
gains in isometric strength at those joint angles than training
dynamically.
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Isometric training at four joint angles did not result in the
highly angle-specific adaptations that have been reported for
isometric training at just one joint angle.
What are the practical implications?
Both isometric and isokinetic training do not build strength equally at all
joint angles.
Therefore, if your sport or task requires strength at a specific joint angle:It will be necessary to look at targeted methods of increasing the strength
at that specific angle - either by partials, eccentrics, isometrics (long or
short lengths) or by dynamic exercises that stress a particular ROM.
The same considerations will apply to strength rehabilitation programs.
Rehabilitation - training isometrically
through a range of angles
Since isometric training has been found to generate great increases in
strength that are limited to specific joint angles, it is possible that
training isometrically at a range of angles might be more effective over
the whole ROM at a joint than dynamic training.
Particularly useful in Rehabilitation.
Isometric exercise does not, contrary to popular opinion, increase muscular endurance
or functional capacity in real world situations.
They are, however, very effective if a muscle shows weakness at particular point in
range.
This is most commonly seen in rehabilitation especially after surgery.
Here there will often be points through range where strength is limited and can be
seen on the graphs produced by a dynamometer.
Training at these points using isometric exercise will in fact restore the strength
deficiency and is the fastest way to address these perturbations in the curves seen on
those graphs.
The extreme effort involved with isometric exercises causes considerable internal
pressure both within the muscles themselves and in the abdominal and thoracic
cavities.
Isometric exercise can increase blood pressure and heart rate to levels that
would be dangerous for anyone with undiagnosed cardiac problems.
(Nagle, Seals and Hanson 1988, White and Carrington 1993 and Baum et al.
1995), whilst also increasing intra abdominal pressure to dangerously high levels
(Williams and Lind 1987).
For those in good health this is not problematic however, for those who have
suffered muscular or tendonous injuries the consequences can be dire.
Isometric exercises are, however, extremely good for strengthening muscle
groups around an injured joint as the joint surfaces actually distract from one
another during isometric contraction.
However, following isometric exercise there is a decrease of muscle power by
up to 60-70% (Tidas and Shoemaker 1995), this can last for up to 4 days.
During this time the associated joints are exposed to much higher than normal
impact and sheer forces as they have lost one of their most vital protective
mechanisms.
This could lead to discomfort as demonstrated by Melchionda et al. (1984)
which is not experienced with isokinetic concentric contractions (Dvir 1995).
In reality electrical stimulation of a muscle is more effective at increasing
muscular strength than isometric exercise as has been shown by:
Draper and Ballard (1991).
Advantages - Disadvantages
Advantages:
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Does not aggravate sensitive joint surfaces.
Easy to perform and remember.
Convenient.
Reproducible.
Easy to measure.
Cost effective.
Disadvantages:
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Not Functional.
Any improvements are speed and angle specific.
Many Contraindications.
Poor efficiency for strength enhancements.
No endurance enhancements.
Concentric - Eccentric
Concentric (n) is a term used to describe a type of movement or exercise.
Translated literally concentric means “towards the centre”.
Eccentric (n) is a term used to describe a type of movement or exercise.
Translated literally eccentric means “away from the centre”.
Concentric
This type of contraction occurs when the tension generated within a muscle is
sufficient to overcome a resistance (in most cases at least gravity) to move a body
segment (or the attachment of the muscle on that body segment) towards another
segment (or the origin of the muscle in question) or vice versa.
This type of contraction is dependent on one end of the muscle having more stability
than the opposite end.
The term dynamic shortening seems to be a more appropriate way of describing
concentric contractions.
A good example is a concentric contraction of the biceps muscles in the arm.
Here the concentric contraction shortens the bicep which pulls on the elbow bending
it. Hence a concentric contraction of the biceps bends the elbow.
Concentric contractions tend to be the weakest contractions we can produce with
isotonic concentric contractions normally weaker (due to lever dis-advantage) than
isokinetic concentric contractions.
Eccentric
Whenever a muscle lengthens it generates a contractile force meaning all movements
in the body occur with some muscular activity (this is absolute).
The term lengthening is actually misleading as in most instances the muscle does not
actually lengthen.
In reality it returns from its shortened condition to its normal resting length.
In most instances in which muscles contract eccentrically they actually act as a brake
or resistive force against the moving force of gravity or other external force (like a
weight).
In truth most eccentric contractions are more energetic and hence more positive than
concentric contractions.
Eccentric actions produce greater loading of the elastic musculoskeletal
components and are used during many dynamic movements (like walking down
stairs or hitting a ball).
As the majority of muscle tears are thought to occur during eccentric motions
improvements in this performance may be beneficial for injury prevention.
(Bennett and Stauber 1986)
However, eccentric motions produced by active dynamometers are not
considered to be like those seen during functional activities (they are described
by Chan and Maffulli 1996 as 'unnatural').
Short and rapid eccentric motions are normally produced during daily and
sporting activities, isokinetically this is not seen as the movements are usually
long and through full range of motion.
Eccentric actions are responsible for deep onset muscle soreness (the soreness
after going to the gym or training).
A good example is an eccentric contraction of the quadriceps muscles in the leg whilst
walking down stairs.
Here the eccentric contraction allows the knee to bend under control which allows a
safe decent of the stairs.
We can control the speed of the lengthening by using more or less muscular units.
Eccentric contractions tend to be the strongest contractions we can produce with
isotonic eccentric contractions normally weaker (due to lever dis-advantage) than
isokinetic eccentric contractions.
Order of Strength
The order of strength describes how much torque (strength) we can produce in the
various exercises or tests if the test is the same.
For example if we tested bicep strength we would get the lowest result in a standard
isotonic concentric test.
If we repeated the same bicep test isokinetically the results would be higher (for
peak torque).
If we then went on and measured isometrically the results would be even higher (as
long as the angle of mechanical and muscular efficiency was chosen).
The eccentric actions always offer the highest levels of torque.
Or in other words we are stronger in eccentric actions than in concentric and
isometric actions.
Order of Strength continued
Why we are stronger eccentrically is not fully understood one theory is that
“ when the muscle lengthens you have the strength of the contractile elements (the
concentric in other words) and added to that is the elasticity of the non-contractile
elements (Z disks etc. which stretch)”.
This added stretch gives a higher value in eccentric actions.
Remember eccentric actions actually damage the micro filaments (actin and
myosin) and give delayed onset muscle soreness if done enough.
Order of Strength continued
HIGHEST
Isokinetic eccentric
Isotonic eccentric
Isometric
Isokinetic concentric
Isotonic concentric
LOWEST
(Adapted from Davies, 1984)
Isokinetic Contraindications
Please note this is not an extensive list only a guide.
Caution must be taken as some forms of isokinetic testing / exercising are
harder than others.
Hence a form of test / exercise that may be appropriate for one individual may
not be appropriate to another.
Prudent judgment should be used.
Absolute Contraindications
None united fractures to limb
Epilepsy
Cardiac insufficiency (unless monitored)
Severe peripheral vascular disease
Aneurysms
Anticoagulants
Recent (< 3 months previous) X-ray/chemo therapy
Long term steroid use (> 3 months)
Acute (< 7 days) muscle/ligament tear (>grade I)
Pregnancy
Any neurological condition (e.g. stroke, Parkinson's disease) unless closely
monitored
 Skin problems under load cell
 Severe osteoporosis
 Malignancy (in area to be tested)
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Relative Contraindications
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Pain
Limited range of motion (severe)
Soft tissue healing
Bone healing
Effusions
Osteoporosis
Anaemia
Rheumatoid arthritis
Recent surgery (discretion must be used)
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