Fatigue is a complex phenomenon involving different mechanisms (central and peripheral). The study of fatigue under neuromuscular electrical stimulation (NMES) has been ignored for a long time, due to the assumption that since NMES is applied over the peripheral level of the neuromuscular system, it cannot implicate central nervous system reactions. However, several arguments in the literature point to a real implication of central structures during NMES. This led to the study of the electrically induced fatigue and results show that supra-spinal fatigue is developed after both high- and low-frequency stimulation, further proving the non-purely peripheral character of this technique.