The Effect of Age and Seat Height on Sit-to-Stand Transfer Biomechanics and Muscle Activation

Objective: To determine the effects of age and seat height on lower limb biomechanics and electromyography (EMG) during a sit-to-stand (STS). Methods: 10 older and 10 younger adults performed five STS trials from normal knee height and raised height. Bilateral lower limb and trunk motion, ground reaction forces and EMG were measured. Two-way analysis of variance tested for main effects (group, height) and interactions (alpha = 0.05). Results: Older adults had significantly greater peak and integrated EMG of most muscles (27–125%). Normal seat height had significantly greater peak angles, hip and knee flexion moments, and peak and integrated EMG of most muscles. Conclusion: Despite similar biomechanics, older adults had greater EMG activity, supporting greater relative muscular demands during STS. The raised seat height reduced hip and knee biomechanical demands and muscle activity. This study is the first to provide evidence of age-related changes in muscle activation during a STS from different seat heights.