Download Chapter 8: Regaining Stability and Balance

Regaining Postural Stability &
Balance
Chapter 7
• Factors that impact balance
– Muscular weakness
– Proprioceptive deficits
– ROM deficits
• Balance is critical in dictating movement
strategies within the closed kinetic chain
• Balance is a highly integrated dynamic process
• Postural equilibrium is a broader term that
incorporates alignment of joint segments
– Maintaining CoG within the limits of stability (LOS)
• Vital component in rehabilitation
– Joint position sense, proprioception and kinesthesia
Postural Control System
• Components
– Sensory detection of body motions
– Integration of sensorimotor information within the
CNS
– Execution of musculoskeletal responses
• Balance is a static and dynamic process
• Disrupted balance occurs due to two factors
– Position of CoG relative to base of support is not
accurately sensed
– Automatic movements required to maintain the CoG
are not timely or effective
• Body position in relation
to gravity is sensed by
– Visual
– Vestibular
– Somatosensory inputs
• Balance movements
involve a number of joints
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Ankle
Knee
Hip
Coordinated movement
along kinetic chain
Control of Balance
• Tall body vs. Small base of support
– Balance relies on network of neural connections
• Postural control relies on feedback
• CNS involvement
– Sensory organization
• Determines timing, direction and amplitude of correction
based on input
• System relies on one sense at a time for orientation
• For adults the somatosensory system is relied on primarily
– Muscle coordination
• Collection of processes that determine temporal sequencing
and distribution of contractile activity
• Balance deficiencies
– Inappropriate interaction among 3 sensory inputs
• Patient that is dependent on one system may be presented
with inter-sensory conflict
• Sensory Input
– Somatosensory
• Provides information concerning relative position of body
parts to support surface and each other
– Vision
• Measures orientation of eyes and head in relation to
surrounding objects
• Role in maintenance of balance
– Vestibular
• Provides information dealing with gravitational, linear and
angular accelerations of the head with respect to inertial
space
• Minor role when visual and somatosensory systems are
operating correctly
Somatosensation as it Relates to
Balance
• Global term used to describe proprioception
• Specialized variation of the sensory modality of
touch, encompassing joint sense (kinesthesia)
and position
• Process
– Input is received from mechanoreceptors
– Stretch reflex triggers activation of muscles about a
joint due to perturbation
• Results in muscle response to compensate for imbalance
and postural sway
– Muscle spindles sense stretch in agonist, relay
information afferently to spinal cord
– Information is sent back to fire muscle to maintain
postural control
Balance as it Relates to the Closed
Kinetic Chain
• Balance
– Process of maintaining body’s CoG within base of
support
– Body’s CoG rests slightly above the pelvis
• Kinetic chain
– Each moving segment transmits forces to every other
segment
– Maintaining equilibrium involves the closed kinetic
chain (foot = distal segment  fixed beneath base of
support)
• Automatic postural movements
– Determined via indirect forces created by muscles on
neighboring joints
• Inertial interaction forces among body segments
– Series of strategies are involved to coordinate
movement (joint strategies)
• Injury to joints or corresponding muscles can result in loss of
appropriate feedback
Balance Disruption
• In the event of contact body must be able to
determine what strategy to utilize in order to
control CoG
– Joint mechanoreceptors initiate automatic postural
response
• Selection of Movement Strategy
– Joints involved allow for a wide variety of postures
that can be assumed in order to maintain CoG
• Forces exerted by pairs of opposing muscles at a joint to
resist rotation (joint stiffness)
• Resting position and joint stiffness are altered independently
due to changes in muscle activation
• Myotatic reflex is earliest mechanism for activating muscles
due to externally imposed joint rotation
• Ankle Strategy
– Shifts CoG by maintaining feet and rotating body at a
rigid mass about the ankle joints
• Gastrocnemius or tibialis anterior are responsible for torque
production about ankle
• Anterior/posterior sway is counteracted by gastrocnemius
and tibialis anterior, respectively
– Effective for slow CoG movements when base of
support is firm and within LOS
– Also effective when CoG is offset from center
• Hip Strategy
– Relied upon more heavily when somatosensory loss
occurs and forward/backward perturbations are
imposed or support surface lengths are altered
– Aids in control of motion through initiation of large and
rapid motions at the hip with anti-phase rotation of
ankle
– Effective when CoG is near LOS perimeter and when
LOS boundaries are contracted by narrower base of
support
• Stepping Strategy
– Utilized when CoG is displaced beyond LOS
– Step or stumble is utilized to prevent a fall
• Instance of musculoskeletal abnormality
– Damaged tissue result in reduced joint ROM causing
a decrease in the LOS and placing individual at a
greater risk for fall
– Research indicates that sensory proprioceptive
function is affected when athletes are injured
Assessment of Balance
• Subjective Assessment
– Traditionally assessed via the Romberg Test
• Feet together, arms at side, eyes closed
• Loss of proprioception is indicated by a fall to one side
• Lacks sensitivity and objectivity, qualitative assessment
• Balance Error Scoring System (BESS)
– Utilizes three stances
• Double, single, tandem on both firm and foam surfaces
– Athletes are instructed to remain motionless with
hands on hips for 20 seconds
– Unnecessary movements and correction of body
position are counted as ‘errors’ (max score = 10)
– Results are best utilized if compared to baseline data
• Semi-dynamic and dynamic tests
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functional reach tests
timed agility tests
carioca
hop test
Bass test for dynamic balance
Timed T-band kicks
Timed balance beam walks (eyes open and closed)
• While criticized for merely reporting time of posture
maintenance, angular displacement or distance covered –
test can provide valuable information about function and
return to play capability
Objective Assessment
• Balance systems
– Provide for quantitative assessment and training
static and dynamic balance
– Easy, practical and cost-effective
– Utilize to assess:
• Possible abnormalities due to injury
• Isolate various systems that are affected
• Develop recovery curves based on quantitative measures in
order to determine readiness to return
• Train injured athlete
– Computer interfaced force-plate technology
• Vertical position of CoG is calculated
– Vertical position of
CoG movement =
indirect measure of
postural sway
– Multiple manufacturers
– Frequent consultation
may be required with
manufacture to
decipher conflicting
terminology between
manufacturers
– Force plate measures
• Steadiness, symmetry,
dynamic stability
– Steadiness
• Ability to keep body as motionless as possible
• Measure of postural sway
– Symmetry
• Ability to distribute weight evenly between 2 feet in upright
stance
• Measures center of pressure, center of balance and center of
force
– Dynamic stability
• Ability to transfer vertical projection of CoG around a
stationary supporting base
• Perception of safe limit of stability
– Utilization of external perturbation
• Some are systematic (sinusoidal) while others are
unpredictable and determined via changes in subject sway
– Center of Pressure (CoP)
• Center of the distribution of the total force applied to the
supporting surface
• Calculated from horizontal moment and vertical force data
through a triaxial force platform
– Center of Balance (CoB)
• Point between feet where the ball and heel of each foot has
25% of the body weight (Chattecx Balance System)
• Relative weight positioning
– Center of Vertical Force (CoF)
• Center of vertical force exerted by the feet against the
support surface (Neurocom’s Equitest)
– Total force applied to the platform fluctuates due to
body weight and inertial effects of body movement
– Forces based on motion of CoG
– Athlete should maintain their CoP near A-P and M-L
midlines
• Additional Balance Parameters
– Postural sway
• Deviation from CoP, CoB, or CoF
• Determined using mean displacement, length of sway path,
length of sway area, amplitude, frequency and direction
relative to CoP
– Equilibrium Scores
– Sway index (SI)
• Scatter of data about CoB (Chattecx)
• Forceplate technology
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Fully integrated hardware/software
Allowing for static and dynamic postural assessment
Single or double leg stance, eyes opened or closed
Moving visual surround for sensory isolation and
interaction
– Long force plate, dynamic multi-axial equipment
Injury and Balance
• Stretched/damaged ligaments fail to provide
adequate neural feedback, contributing to
decreased proprioception and balance
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May result in excessive joint loading
Could interfere with transmission of afferent impulses
Alters afferent neural code conveyed to CNS
Decreased reflex excitation
• Caused via a decrease in proprioceptive CNS input
• May be the result of increased activation of inhibitory
interneurons within the spinal cord
• All of these factors may lead to progressive
degeneration of joint and continued deficits in
joint dynamics, balance and coordination
• Ankles
– Joint receptors believed to be damaged during injury
to lateral ligaments
• Less tensile strength when compared to ligament fibers
• Results in deafferentation and diminished signaling via
afferent pathways
• Articular deafferentation – reason behind balance training in
rehabilitation
– Orthotic and bracing intervention
• Enhancement of joint mechanoreceptors to detect
perturbations and provide structural support for detecting and
controlling sway
– Chronic ankle instability
– Recovery of proprioceptive capabilities
– Modifications in movement strategies to enhance
proprioceptive input
– Increased postural sway and/or balance instability
may not be due to a single factor
– May be related to both neurological and
biomechanical factors at the ankle joint
• Altered biomechanical alignment – alters somatosensory
transmission
– Deficit in kinetic chain due to instability vs.
deafferentation
• Knee Injuries
– Ligamentous injury has been shown to alter joint
position detection
• ACL deficient subjects with functional instability exhibit this
deficit which persist to some degree after reconstruction
• May also impact ability to balance on ACL deficient leg
– Mixed results have been presented with static testing
• Isometric muscle strength could compensate for
somatosensory deficits
• Definition of functionally unstable may vary
• Role of joint mechanoreceptors with respect to end range
and the far reaches of the LOS
– More dynamic testing may incorporate additional
mechanoreceptor input – results may be more
definitive
• Head Injury
– Balance has been utilized at a criterion variable
– Additional testing is necessary in addition to balance
and sensory modalities
– Postural stability deficits
• Deficits may last up to three days post-injury
• Result of sensory interaction problem - visual system not
used effectively
– Objective balance scores can be utilized to determine
recovery curves for making return to play decisions
Balance Training
• Vital for successful return to competition from
lower leg injury
– Possibility of compensatory weight shifts and gait
changes resulting in balance deficits
• While advanced technology is an amenity,
imagination and creativity are often the best
tools when there are limited resources
• Functional rehabilitation should occur in the
closed kinetic chain – nature of sport
• Adequate and safe function in the open chain is
critical = first step in rehabilitation
• Rules of Balance Training
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Exercise must be safe and challenging
Stress multiple planes of motion
Incorporate a multisensory approach
Begin with static, bilateral and stable surfaces and
progress to dynamic, unilateral and unstable surfaces
– Progress towards sports specific exercises
• Utilize open areas
• Assistive devices should be in arms reach early
on
• Sets and repetitions
– 2-3 sets, 15  30 repetitions or 10 of the exercise for
15 sec.  30 seconds later on in program
Classification of Balance Exercises
• Static
– CoG is maintained over a fixed base of support, on a stable surface
• Semi-dynamic
– Person maintains CoG over a fixed base of support while on a
moving surface
– Person transfers CoG over a fixed base of support to selected ranges
and or directions within the LOS, while on a stable surface
• Dynamic
– Maintenance of CoG within LOS over a moving base of support while
on a stable surface (involve stepping strategy
• Functional
– Same as dynamic with inclusion of sports specific task
• Phase I
– Non-ballistic types of drills
– Static balance training
– Bilateral to unilateral on
both involved and
uninvolved sides
– Utilize multiple surfaces to
safely challenge athlete
and maintaining motivation
– With and without
arms/counterbalance
– Eyes open and closed
– Alterations in various
sensory information
– ATC can add perturbations
– Incorporation of multiaxial
devices
– Train reflex stabilization
and postural orientation
• Phase II
– Transition from static to dynamic
– Running, jumping and cutting – activities that require
the athlete to repetitively lose and gain balance in
order to perform activity
– Incorporate when sufficient healing has occurred
– Semi-dynamic exercised should be introduced in the
transition
• Involve displacement or perturbation of CoG
• Bilateral, unilateral stances or weight transfers involved
• Sit-stand exercises, focus on postural
Bilateral Stance Exercises
– Unilateral Semidynamic exercises
• Emphasize
controlled hip flexion,
smooth controlled
motion
• Single leg squats,
step ups (sagittal or
transverse plane)
• Step-Up-And-Over
activities
• Introduction to
Theraband kicks
• Balance Beam
• Balance Shoes
• Phase III
– Dynamic and functional types of exercise
– Slow to fast, low to high force, controlled to
uncontrolled
– Dependent on sport athlete is involved in
– Start with bilateral jumping drills – straight plane
jumping patterns
– Advance to diagonal jumping patterns
• Increase length and sequences of patterns
– Progress to unilateral drills
• Pain and fatigue should not be much of a factor
– Can also add a vertical component to the drills
– Addition of implements
• Tubing, foam roll,
– Final step = functional activity with subconscious
dynamic control/balance
Phase III Exercises
Clinical Value of High-Tech
Training and Assessment
• Balance systems allow
for deficit detection and
quantitative assessment
• Utilize both in the
clinical setting and
research setting
– Multiple tests and
variables can be
assessed and monitored
with respect to
performance