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Evidence-Based Balance Rehabilitation and Fall Prevention: Summary
• Primarily proprioception but also tactile sensation: ○ As proprioception is lost, more reliance on tactile information from plantar surfaces of feet is substituted Vision • Next fastest modality of balance after somatosensation • Relies heavily on near field perception (within 10 feet) • Peripheral visual fields are more sensitive to motion (higher density of rods) Vestibular • Slowest modality for balance reactions • Works intimately with visual system for coordinating eye movement with head motion (vestibulo-ocular reflex) • Determining vertical orientation: Subjective postural vertical Supplementary Modalities • Auditory: Use of stereo input to determine surroundings • Visceral proprioceptors: A full stomach affects balance PROCESSING BALANCE Verticality • Multiple centers involved, including: ○ Cerebellum and brainstem: Integrating vestibular and visual information into a balance set ○ Thalamus, vestibular cortex, limbic system, and basal ganglia: Integrating somatosensory information into balance set Sensory Weighting The nervous system selectively “weights” sensory modalities based on reliability— sometimes maladaptively: • Normal : Relying more on vestibular and somatosensory information in low-light situations: ○ With proprioception loss, many older adults can become more dependent on tactile information
INTRODUCTION
Human Balance is Unique • Primarily move bipedally versus quadruped • Aligned vertically over a small base of support • Relies on constant monitoring and control of sway over flexible segments • Rapid adjustments of center of mass (running, jumping, changes of direction) Balance is the maintenance of upright posture for the purpose of functional activity within one’s environment. BALANCE REQUIREMENTS • Perception : Possess accurate perception of external forces (gravity) and internal forces (positioning of the body) • Processing : Capacity to develop strategies for managing body movements • Motor capacity and control : Ability to execute movement with adequate range of motion and strength/power while simultaneously controlling center of mass • Feedback and error correction : Ability to assess and correct for errors in movement and unexpected challenges/perturbations Balance Perception • Three main sensory modalities : Vision, vestibular, somatosensation (tactile sense and proprioception) • Supplementary sensory modalities : Auditory, visceral graviception Somatosensation • Primary information from contact with support surface (feet in standing) • Secondary information from other joints (knees, hips, spine) • Can supplement this information from upper extremities/other body parts • Tactile information from a single fingertip can greatly inform balance
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