EMG-force relationships in skeletal muscle.

This article reviews the history of attempts to define in quantitative terms the relationship between a processed electromyographic signal and the corresponding force produced by skeletal muscle. Numerous reports have indicated a linear relationship between isometric force and rectified, integrated EMG. These reports, the nature of their experiments, and the disagreements among them are reviewed. Particular attention is given to the effects of the signal processing in the final results, including type and location of electrodes, amplification, signal isolation, etc. The effect of joint position and level of muscular effort in the isometric case are discussed. Various proposed mathematical models of the force-EMG relationship are presented and analyzed. The concluding section of the paper summarizes the current areas of agreement and disagreement and comments on the feasibility of obtaining force-EMG relation in the presence of movement.