Myoelectric signal as a quantitative measure of muscle mechanical output

The estimation of muscle tension and velocity of shortening from the myoelectric signal have been considered in numerous papers. These papers consider the estimates of each variable separately, with the other appearing in the estimation as a constant parameter. The work described in this paper develops a model for the relationship between a muscle’s mechanical outputs and the myoelectric signal. The model suggests that the myoelectric signal is related directly to the muscle mechanical power via a nonlinear differential equation in velocity of shortening. The model is general in that it includes as special cases the isometric and anisometric constant-velocity work of other authors and agrees with their experimental results. In this work anisometric experiments are performed on the biceps brachii muscle to verify the model. Estimates of muscle velocity of shortening and mechanical power are obtained from the myoelectric signal during anisometric contractions and the results agree well with the actual velocity and power. The model points out that the myoelectric signal is a direct measure of muscle tension only under isometric conditions.