Regaining Postural Stability & Balance Chapter 7.

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Regaining Postural Stability & Balance Chapter 7

Transcript of Regaining Postural Stability & Balance Chapter 7.

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Regaining Postural Stability & Balance

Chapter 7

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• 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

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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

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• Body position in relation to gravity is sensed by– Visual– Vestibular– Somatosensory inputs

• Balance movements involve a number of joints– Ankle– Knee– Hip– Coordinated movement

along kinetic chain

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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

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• 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

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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

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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)

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• 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

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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

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• 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

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• 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

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• 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

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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

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• Semi-dynamic and dynamic tests – 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

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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

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– 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

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– 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

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– 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

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• 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– 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

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Injury and Balance

• Stretched/damaged ligaments fail to provide adequate neural feedback, contributing to decreased proprioception and balance– 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

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• 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

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– 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

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• 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

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• 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

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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

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• Rules of Balance Training– 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

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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

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• 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

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• 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

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Bilateral Stance Exercises

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– Unilateral Semi-dynamic 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

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• 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

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Phase III Exercises

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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