Sex-independent and sex-dependent effects of older age on motor input variability during preferred-speed gait

High variability of gait motor output, such as stride time variability, occurs with aging and is a factor associated with falls in aging males and females. The mechanism is currently unclear but may be clarified by examining motor input variability. Males and females from 20 to 82 years of age completed gait trials at their preferred speed; Motor input variability was quantified as the electromyography (EMG) variability from stride-to-stride. This variability was extracted for several muscles and gait phases. Higher age was associated with higher EMG variability, independent of sex, except for mid-stance where higher age was associated with lower gastrocnemius lateralis variability in females. Results indicate sex-independent and sex-dependent associations of older age with motor input variability, which may contribute to sex differences in motor output variability during gait.