Age and gender differences in peak lower extremity joint torques and ranges of motion used during single-step balance recovery from a forward fall.

Previous studies have found substantial age and gender group differences in the ability of healthy adults to regain balance with a single step after a forward fall. It was hypothesized that differences in lower extremity joint strengths and ranges of motion (ROM) may have contributed to these observed differences. Kinematic and forceplate data were therefore used with a rigid-link biomechanical model simulating stepped leg dynamics to examine the joint torques and ROM used by subjects during successful single-step balance recoveries after release from a forward lean. The peak ROM and torques used by subjects in the study were compared to published estimates or measured values of the available maxima. No significant age or gender group differences were found in the mean ROM used by the subjects for any given initial lean angle. As initial lean angle increased, larger knee ROM and significantly larger hip ROM were used in the successful recoveries. There were substantial gender differences and some age group differences in peak lower extremity joint torques used in successful recoveries. Both young and older females often used nearly maximal joint torques to recover balance. Subjects' maximum joint strengths in plantarflexion and hip flexion were not good predictors of single-step balance recovery ability, particularly among the female subjects.

Age and gender differences in single-step recovery from a forward fall.

BACKGROUND: Previous work has found that healthy older men were significantly less able than young male adults to recover balance by taking a single rapid step upon sudden release from forward leans. In light of the higher rates of falls and fall-related injuries among older women compared to older men, we hypothesized that healthy older women would perform more poorly than either female young adults or older men in this test of abilities to recover balance rapidly. METHODS: Ten young (mean age 25.0 years) and 10 older (73.7 years) healthy women were released from forward leans and instructed to regain standing balance by taking a single step forward. The lean angle was incrementally increased from its smallest value, approximately 14 degrees, until the subject failed to regain balance as instructed. Lower extremity kinematics were measured, and findings were compared with those of the earlier study of healthy young and old men. RESULTS: Five of the 10 older women could not recover balance with a single step after release from the smallest of the imposed forward leans. For the 5 older women who succeeded in recovering as instructed from at least one lean, the mean maximum lean angle was significantly smaller than that for young women (16.2 degrees vs 30.7 degrees, p < .001) or older men (16.2 degrees vs 23.9 degrees, p = .014). In contrast, there was no significant difference in mean maximum lean angle between female and male young adults. CONCLUSIONS: Healthy older women, compared to either young women or older men, were significantly less able to recover balance by taking a single rapid step during a forward fall. The decreased abilities of older women appeared to result from limitations in the maximum speeds at which they moved their swing foot during recovery.

Age differences in using a rapid step to regain balance during a forward fall.

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.