Chapter 8 Impaired Balance Copyright 2005 Lippincott Williams

Balance v Foundation of coordination v Center of gravity (COG) constantly shifts over base of support (BOS) v If sway exceeds limits of stability = compensation v If sway is within limits of stability = postural stability

Postural Stability v Ability to maintain the COG within stability limits. v Normal anterior/posterior sway – 12 degrees from most posterior-anterior position. v Lateral sway 16 degrees from side to side. v If sway exceeds boundaries, compensation is employed to regain balance. A smaller envelope is created and tolerated. Copyright 2005 Lippincott Williams & Wilkins

Physiology of Balance – Envelope of Sway Copyright 2005 Lippincott Williams & Wilkins

Contribution of Sensory Systems Copyright 2005 Lippincott Williams & Wilkins

Somatosensory v Free nerve endings v Ruffini endings v Paciniform corpuscles v Golgi-Mazzoni corpuscles

Visual and Vestibular Neurophysiology Visual Provides sensory information regarding the position of the head relative to the environment, and orients the head to maintain level gaze. Vestibular Provides information regarding orientation of the head in space and acceleration. Copyright 2005 Lippincott Williams & Wilkins

Processing Sensory Information Visual Peripheral information Vestibular Cerebellum Basal ganglia Supplemental motor area Motor

Response Strategies (Ankle, Hip, Stepping) Ankle Strategy Used when displacements are small. v Displaces COG by rotation about the ankle joint. v E. g. , Posterior displacement of COG – Dorsiflexion at ankle, contraction of anterior tibialis, quadriceps, abdominals. v Anterior COG displacement – Plantar flexion at ankle, contraction of gastrocnemius, hamstring, trunk extensors. v Copyright 2005 Lippincott Williams & Wilkins

Hip Strategy Employed when ankle motion is limited, displacement is greater, when standing on unstable surface that disallows ankle strategy. 2. Preferred when perturbation is rapid and near limits of stability. 3. Post. Displacement COG – Backward sway, activation of hamstring and paraspinals. 4. Ant Displacement COG – Forward sway, activation of abdominal and quadricep muscles. 1. Copyright 2005 Lippincott Williams & Wilkins

Stepping Strategy v If displacement is large enough, a forward or backward step is

Motor Learning Cognitive Phase What to do Associative Phase How to do it better

Causes of Impaired Balance v Injury or disease of eyes, inner ear, peripheral receptors, spinal cord, cerebellum, basal ganglia, cerebrum, etc. v Injury or damage to knee, ankle, hip, and back v DJD v CVAs, tumors, visual field loss v Age Copyright 2005 Lippincott Williams & Wilkins

Effects of Training On Balance v Improvements in balance measures v Improvements in lower extremity strength v Effective in reducing the effect of, or exposure to, risk factors for falling in the elderly Copyright 2005 Lippincott Williams & Wilkins

Examination and Evaluation of Impaired Balance (3 categories) 1. 2. 3. Balance during functional activities with or without assistive devices. Balance (static or dynamic) with or without use of assistive devices. Safety during gait, locomotion, or balance. Copyright 2005 Lippincott Williams & Wilkins

Examination and Evaluation of Impaired Balance v Standing with eyes open – fixed platform v Standing blindfolded – fixed platform v Sway-referenced vision w/fixed support v Normal vision w/sway-referenced support v Sway-referenced vision and support Copyright 2005 Lippincott Williams & Wilkins

Six Balanced Testing Situations Copyright 2005 Lippincott Williams & Wilkins

Activities for Treating Impaired Balance Most important factor is determining cause of impairment Strength Base Motor control Modulator element Fear Cognitive/affective Copyright 2005 Lippincott Williams & Wilkins

Mode – Graduated Intervention v Begin with weight shifts on a stable surface v

Posture v Often includes “core” stability training to improve COG control and sense of trunk posture v Begin in supine or seated position v Over sessions, use a variety of arm positions, unstable surfaces, single leg stances, etc. Copyright 2005 Lippincott Williams & Wilkins

Movement v Adding movement patterns to acquired stable static postures increases balance challenge. v Add ant. /post. sway to increase stability limits. v Trunk rotations and altered head positions alter vestibular input. v PNF techniques during trunk rotation. v Stepping back/forward assists in re-stabilization exercises. Copyright 2005 Lippincott Williams & Wilkins

Dosage – Environment Depends on patient’s situation Elderly – most training, in clinic v Progress to types of external environment patients will face when they leave the clinic. Active individuals – Balance activities may be carried out at home or at local health club. Copyright 2005 Lippincott Williams & Wilkins

Sequence BOS – Advance from wide to narrow base Posture – Stable to unstable posture (sway) Visual – Closing of the eyes COG – Greater disruption to elicit hip or stepping strategy Progress to more dynamic activities, unstable surfaces, and complex movement patterns. Copyright 2005 Lippincott Williams & Wilkins

Perturbation Extrinsic feedback (e. g. , mirrors) Balance and movement control Intrinsic Development of

Contraindications and Precautions v Persons who are inherently in balancedchallenged positions. v Eliminate obstacles

Summary ü Balance is an important component of coordination. ü Aging is associated with balance impairment and places the elderly at risk for falls. ü Balance is a function of the triad of visual, vestibular, and somatosensory systems. Copyright 2005 Lippincott Williams & Wilkins

Summary (cont. ) ü Ankle strategies are used in response to small perturbations. ü Hip and stepping strategies counter larger perturbations. ü Treatment should be aimed at the cause – biomechanical, sensorimotor, or both. Copyright 2005 Lippincott Williams & Wilkins