POSTURAL SENSITIVITY TO VISUAL FLOW IN AGING ADULTS WITH AND WITHOUT BALANCE PROBLEMS

Background. This study tested balance behavior of young adults and agi ng adults with and without balance problems in response to visual flow from a moving visual surround. Methods. Balance behavior was indexed by force plate measures of maximum anterior/posterior displacement of the center of foot pressure and horizontal shear forces. The sample in cluded normal young adults (n = 13; mean age 23 years, +/- 7.5), norma l aging adults (n = 13; mean age 76 years, +/- 6.5), and aging adults with balance problems not directly attributable to a diagnosable neuro logical disease or dysfunction (n = 13; mean age 79 years, +/- 5.8). R esults. The balance-affected aging group had statistically greater swa y responses than the young group when the stimulus was unexpected (as in the first trial; p < .05). Some individuals in each group had large responses that were statistical outliers from the group median. The b alance-affected group had significantly greater shear forces than the young group. Conclusions. Greater sway responses suggest over-reliance on visual cues for posture control in the balance-affected aging grou p, which may be related to underlying, borderline somatosensory defici ts, as indicated by the patterns of subclinical indications for somato sensory impairments on neurological exams in this group. Visually sens itive postural control, however, may issue from several different unde rlying processes. Elevated shear forces during balance responses in th e balance-affected group suggest a greater use of hip movements in add ition to ankle movements for postural adjustments.