Reliability of the log-transformed EMG amplitude-power output relationship for incremental knee-extensor ergometry

Introduction: The purpose of this investigation was to determine the reproducibility of the log-transformed model for electromyography (EMG) amplitude during incremental single-leg knee-extensor exercise. Methods: Eight healthy college-aged men performed 3 incremental tests on separate occasions on a knee-extensor ergometer. EMG amplitude was analyzed for each participant on each occasion for the rectus femoris and vastus medialis muscles at 4 different exercise power outputs (30%, 50%, 70%, and 90%) corresponding to each participant's maximal power output. Intraclass correlation coefficients (ICC) were determined for the slope and y-intercept terms derived from the log-transformed EMG amplitude-power output relationship for each muscle. Results: The ICC values for the rectus femoris (slope=0.779; y-intercept=0.787) and vastus medialis (slope=0.756; y-intercept=0.763) muscles were high. Conclusions: The log-transformed EMG amplitude-power output relationship is a reliable index for measuring motor unit activation. Muscle Nerve 52:428-434, 2015