The physical therapist's assessment of standing balance is a necessary component to the treatment of postural instability in the neurologically impaired individual. Research has shown that the instability experienced by many neurologically impaired individuals is a result of inappropriate interaction among the three major sensory systems (somatosensory, visual, and vestibular) that provide orientation information to the postural control system. Very few studies, however, have documented the effects of changing sensory information on the postural control system of normal individuals across a bro~d spectrum of ages. This normative, descriptive study was designed for the purpose of determining how postural stability changes with age when individuals are presented with altered sensory environments.
Fifty eight normal, healthy individuals, 17 males and 41 females, ranging in age from 18 to 84 years, participated in this study. In the study each subject was exposed to six different sensory conditions which were designed by Dr. Ann Shumway-Cook and Dr. Faye Bahling Horak. For each of those six different sensory conditions, in which somatosensory and/or visual information was in some way altered, each subject was measured for standing postural sway area. A computerized standing forceplate, developed by Lewis Nashner, ScD at Neurocom International Inc. was used for measuring total postural sway area for each 3D-second testing condition.
A Student's unpaired two-tailed t-test indicated that under all six sensory conditions, individuals 60 years and older showed significantly greater postural sway than that of individuals younger than 60. In addition, under conditions of greatest intersensory conflict in which support-surface input was inaccurate and visual input was either eliminated or inaccurate, older individuals showed significantly greater changes in sway than did younger individuals. These findings suggest that the ability of the aging individual to adjust to alterations in sensory environments and to maintain postural stability under altered sensory conditions declines with age.
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