**3.2. Origin of the EMG signal**

Muscle tissue produce electrical potentials due to action potentials. With electrodes placed on surface or in muscle tissue, muscle action potentials can be determined. Several events must occur before contraction of muscle fibers. Central nervous system activity initiates a depola‐ rization in the motoneuron [59,60]. The depolarization is conducted along the motoneuron to the muscle fiber's motor end plate. At the endplate, a chemical substance is released that diffuses across the synaptic gap and causes a depolarization of the synaptic membrane. This phenomenon is called muscle action potential. The depolarization of the membrane spreads along the muscle fibers producing a depolarization wave that can be detected by recording electrodes [60].
