Regaining Postural Stability & Balance

1. Regaining Postural Stability & Balance Chapter 7

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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)

9. 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

10. 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

11. 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

12. 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

13. 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

14. 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

16. 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

17. 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

18. 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

19. 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

20. 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

21. 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

22. 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

23. 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

24. 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

25. 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

26. 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

27. 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

28. 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

29. 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

30. 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

31. 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

32. Bilateral Stance Exercises

33. 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

34. 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

35. Phase III Exercises

36. 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