Effects of older age and sex on motor output variability at individual joints during gait

Stride time variability in gait is a factor associated with falls in aging adults, especially in females. This sex difference in aging may originate from differences in motor output variability at individual joints. We analysed sagittal plane ankle, knee, and hip joint angles in gait from a large sample of males and females, aged 19-99 years. Cycle-to-cycle variabilities of mean joint angles and ranges-of-motion during several phases of gait were calculated to investigate motor output variability. Older age was associated with lower ankle and hip angle variability, but higher knee angle variability. Males had greater knee angle variability than females, which was enhanced by older age and correlated with stride time variability. Results suggest that higher motor output variability may help explain the risk of falls in older men but not in older women.