biodex BioSway Operation Manual page 66

CONTENTS
A person with impaired vision from a stroke or cataracts will depend less on vision and more on
touch and vestibular feedback for balance. In this case, choice of assistive device, hand railings
for touch, and proper lighting are important. A person with a visual impairment may perform
well in a clinical setting but have difficulty with balance in more complex visual situations that
demand rapid visual interpretation of multiple visual cues. For example, a person may be safe
walking in a quiet, well-lit hallway but be unable to negotiate a busy, noisy hallway filled with
people and equipment.
Vestibular damage or loss can also have a profound effect on balance and postural control.
Vestibular impairment can cause problems with gaze stabilization, including blurred vision,
problems with balance and posture, and vertigo (Shumway-Cook & Woollacott, 2001).
Improper Sensory Selection
Sensory loss may lead to inflexible or improper sensory weighting. A person may depend on
one particular sense for postural control even if that sense leads to further instability (Shumway-
Cook & Woollacott, 2001). You may notice a person walking with head down, carefully watch-
ing every step. In this case, vision is the dominant sense being used for balance. Retraining
would involve improving the use of somatosensory and vestibular input to reduce dependence
on visual input.
abnormal Internal representations
Individuals' perceptions of their limits of stability are difficult to assess and understand. Illness
and injury, including stroke, clearly affect confidence and may alter perceived stability limits. A
person's stability may be affected by fear of falling, even when the physical ability exists to per-
form a task safely. Conversely, individuals may not have an accurate idea of the limits of their
stability and thus have little warning when loss of stability is occurring, leading to falls.
Sensorimotor adaptation
The nervous system has a powerful ability to compensate for actual or perceived disabilities.
Once an injury has occurred, the nervous system immediately goes to work attempting to com-
pensate for neurologic changes, weakness, and loss of function. But the brain doesn't always
choose the best (or even a good) compensation; it chooses the fastest and most efficient in an
attempt to continue functioning. One of the immediate goals of therapy is to help the nervous
system develop strategies and compensations that minimize musculoskeletal damage and maxi-
mize function.
aGe-related chanGeS In balance
Many changes in balance relate to normal aging. Some changes (i.e., slowed gait, decrease in
lower-extremity strength, decreased ROM) can be easily addressed with a daily exercise pro-
gram. Other changes (i.e., declining visual ability, including loss of visual acuity, declining visu-
al fields, light-dark adaptation, increased sensitivity to glare, loss of peripheral vision and depth
perception) are more complex and may require assessment by another healthcare professional
such as an optometrist or ophthalmologist.
Age-related changes in balance are the result of changes in every system in our bodies.
Neurologic changes include slowed response to losses of balance, decreased righting responses,
and abnormal sensory selection or weighting (i.e., overuse of vision or underuse of propriocep-
tion). Orthopedic changes include loss of ankle sway, leading to an increase in the use of the hip
and stepping strategies and lower-foot swing height. Psychomotor changes include loss of confi-
dence (changes in the perceived limits of stability) and a propensity to fall in new or novel situa-
tions, perhaps due to impaired anticipatory mechanisms. Sensory changes include abnormal
sensation (i.e., peripheral neuropathies, abnormal tone, effects of drugs, visual disturbance such
as hemianopsia) and a reduction in the function of the vestibular system of the inner ear
(Shumway-Cook and Woollacott, 2001).
APPENDIX C — C-4 —