Source
Journals of Gerontology. Series A, Biological Sciences & Medical
Sciences.
52(1):M8-13, 1997 Jan.
Abstract
BACKGROUND: Earlier studies showed that healthy old adults have
substantially reduced abilities to develop joint
torques rapidly. We hypothesized that this age decline would reduce
abilities to regain balance once a forward fall is
underway. The present study examined whether aging in fact reduces
ability to regain balance by taking a single, rapid
step upon release from a forward lean. METHODS: Ten young (mean age
24.3 yr) and ten old (72.8 yr) healthy males
were released from a forward-leaning position and instructed to
regain standing balance by taking a single step forward.
Lean angle was successively increased until a subject failed to
regain balance as instructed. Lower extremity motions and
foot-floor reactions were measured during the responses. Total
response time was divided into reaction, weight transfer,
and step times. RESULTS: At small lean angles, responses of old
subjects were similar to those of the young.
However, the mean maximum lean angle from which old could regain
balance as instructed was significantly smaller than
that for young (23.9 vs 32.5 deg, p < .0005). Within each age group,
maximum lean angle correlated strongly with
weight transfer time and step velocity. CONCLUSIONS: Substantial
age-related declines in the ability to regain balance
by taking a rapid step exist among healthy adults when the time
available for recovery is short. The source of the decline
seems largely to lie in the decrease with age of maximum response
execution speed rather than in the sensory or motor
programming processes involved in response initiation.