Multiple innervation of human muscle fibers.

A combination of electrophysiological techniques, including stimulus threshold measurements, coaxial needle recordings of voluntary EMG, and evoked response analysis, has been used to show that the motor innervation of the human biceps brachii has an extensive distribution in the long axis of the muscle. Impulse collision experiments, involving either excitation at two sites or the use of stimuli of graded intensity, have demonstrated that the diffuse muscle innervation is partly a consequence of individual muscle fibers having more than one end-plate.