The effect of step length on young and elderly women's ability to recover balance.

BACKGROUND Stepping is a common technique for balance recovery. Previous studies have shown that elderly adults are less able than young adults to recover balance by stepping, apparently due to reductions in step length and step speed. We sought to clarify these relations by testing the hypothesis that step length and step speed affect the ability of young and elderly women to recover balance. METHODS During experimental trials, we measured the maximum release angle where participants could recover balance using a single forward step of length 15%, 25%, or 35% body height. FINDINGS Both step length and age associated with recovery ability (P<0.001). When step length increased from 15% to 25% body height, the maximum release angle increased by 36% in young participants and 31% in elderly. When step length increased from 25% to 35% body height, the maximum release angle increased 23% in young and 6% in elderly. At all step lengths, maximum release angles were greater in young than elderly women (by 21% at 15% body height, 30% at 25% body height, and 51% at 35% body height). For all but the 15% body height condition, recovery ability correlated with step contact time, which averaged 50-100 ms faster in young than in elderly. INTERPRETATION The ability of young and elderly women to recover balance by stepping is enhanced by taking larger and quicker steps. This should be considered in balance assessment and training.