Estimation of muscle stiffness during one cycle of pedaling exercises using system identification

The aim of this study was to evaluate muscle stiffness during one cycle of pedaling exercises. Electrical stimulation was applied to the vastus lateralis muscle at various clank angles in a resting state and during pedaling exercises. The angles were -30°, +30°, and +90°. The angle of 0° corresponds to top center of the pedal, and the clockwise direction is positive. A mechanomyogram (MMG) was measured with a capacitor microphone. The MMG system was identified using a singular value decomposition method and the poles of the transfer function were calculated. The poles and mass of the vastus lateralis muscle were used to estimate the muscle stiffness. The muscle stiffness increased as the muscle activity increased. In conclusion, it was suggested that muscle stiffness during pedaling exercises changes depending on muscle activity.