Lower extremity muscle activation patterns in sarcopenic older adults during physical performance tests: implications for rehabilitation approaches.

Sarcopenia causes muscle loss and functional decline in older adults, yet the lower limb muscle activation patterns of sarcopenic patients during functional activities remain unclear. This study aims to investigate the differences in muscle activation between sarcopenic and healthy older adults during functional activities and to explore task-specific compensatory neuromuscular strategies. Eight sarcopenic patients and eight age-matched healthy older adults performed the standardized six-meter walk test (6MWT) and five times sit-to-stand test (5STS) with surface electromyography (EMG) used to record activity from eight muscles of the dominant leg. Sarcopenic individuals exhibited lower walking speed (p = 0.005) and shorter stride length (p < 0.001) in 6MWT, as well as longer completion time (p < 0.001) in 5STS. Significant differences in muscle activation (p < 0.05) included: increased proximal muscle activation with decreased distal activation in both tasks; elevated antagonist co-activation during critical movement transitions; and task-specific EMG variability patterns with increased EMG variability during walking but decreased variability during sit-to-stand activities. Sarcopenic individuals demonstrate distinct muscle activation patterns compared to normally aging individuals. Rehabilitation for sarcopenia may benefit from incorporating ankle-strengthening exercises, functional coordination training, and task-specific neuromuscular control strategies with traditional strength-focused approaches.