Biophysics of the Generation of EMG Signals

This chapter describes the basic concepts of generation and detection of EMG signals. Specific emphasis is devoted to the generation of muscle fiber action potentials at the fiber end plates, their propagation along the sarcolemma, and their extinction at the tendons. The chapter addresses the topics of crosstalk between nearby muscles and selectivity of the recording systems. It discusses the relationships between muscle force and the surface EMG. The EMG signal is generated by the electrical activity of the muscle fibers active during a contraction. The signal sources are the depolarizing and repolarizing zones of the muscle fibers. EMG signal features depend on a number of anatomical, physical, and detection system parameters. Considering all the factors related to the volume conductor and the signal sources that influence the characteristics of the EMG signal, a reliable relation between EMG amplitude and force needs a subject specific and condition specific calibration.