Optimization Objective of Old and Young Adults during Overground Walking

Abstract

This study investigates different strategies that the central nervous system might adopt to solve the motor redundancy problem in young and older adults, focusing on metabolic costs, head accelerations, and gait adjustments during overground walking at various speeds. The study addresses gaps in previous research, which primarily focused on younger participants and treadmill-based trials, potentially overlooking natural gait patterns. Ten younger adults (aged 23–28) and five older adults (aged 69–77) completed eight overground walking trials at different speeds, including their preferred walking speed (PWS), predetermined speeds constant for each subject, and variations of their preferred walking speed.

Results showed that younger and older adults had similar preferred walking speeds and comparable metabolic costs when walking at their chosen pace, while younger adults exhibited higher metabolic costs at higher speeds. The PWS did not minimize the metabolic cost for either age group. At their PWS, younger adults both reduced head accelerations and maximized stability, whereas older adults prioritized stability over movement smoothness. Both groups primarily adjusted step frequency rather than step length to accommodate changes in walking speed. Additionally, no significant differences were found in maximum arm swing velocity between the two groups. These findings challenge previous assumptions about age-related differences in walking efficiency and suggest that stability may play a more critical role in gait optimization for older adults. Further research is necessary to uncover the mechanisms driving these adaptations and their impact on gait across the lifespan.