Age-dependent differences in lateral balance recovery through protective stepping

Abstract

Aging appears to present particular problems for lateral balance stability related to falls. Protective stepping is a common strategy for maintaining balance that may be impaired with aging due to changes in neuromusculoskeletal factors. This study assessed the response patterns, kinematics, and single support hip abduction torque during lateral protective stepping for balance recovery in healthy young and elderly adults. Ten healthy elderly and 10 younger adults received stepper-motor driven waist-pulls of bipedal stance applied pseudorandomly to either side. Stepping response strategies were quantified with force platforms and motion analysis. The young responded primarily using a single lateral sidestep with the limb that was initially loaded passively by the waist-pull, while older subjects favored crossover stepping using multiple steps with more inter-limb collisions. When the elderly did use loaded side steps, the steps were longer, slower, and higher and included greater and prolonged lateral trunk motion than in the young. Overall, older subjects produced greater and less rapid stabilizing hip abduction torque during the single support phase. Age-associated differences in lateral balance control through stepping included using a riskier recovery strategy with increased collisions between the limbs, multiple steps, altered first step characteristics and lateral trunk motion during direct sidestepping, and a generally greater support hip torque. The difficulties with lateral balance control in aging may reflect factors such as impaired hip abduction torque-time capacity and lateral trunk mobility/control. Our findings contribute additional knowledge pertaining to the problem of balance dysfunction and falls among the elderly.