A method includes steps of: measuring a variation in joint angle of a knee of a cyclist to obtain joint angle data； sensing a torque applied on a crank of a cycle or pedaling force applied to a pedal of the cycle to obtain force data； measuring an angular position of the crank to obtain crank angle data； measuring an electrical potential variation of a measured muscle of the cyclist to generate a measured EMG signal； estimating activation data and joint moment data based on aforementioned data and characteristics data； converting the activation data into estimated EMG signals based on the measured EMG signal and the activation data； and computing a coactivation parameter based on the aforementioned EMG signals.
