Muscle excitability during sustained maximal voluntary contractions by a separate analysis of the M‐wave phases

This study was designed to examine separately the changes in the first and second phases of the muscle compound action potential (M‐wave) during and after a sustained 3‐minutes maximal voluntary contraction (MVC). M‐waves were evoked by supramaximal single shocks to the femoral nerve given at 10‐seconds intervals throughout a sustained isometric 3‐minutes MVC and also during six brief MVCs performed throughout a 30‐minutes recovery period. The amplitude, duration, and area of the M‐wave first and second phases, together with muscle conduction velocity and force, were measured. During the 3‐minutes MVC, the amplitude of the first phase increased progressively for the first minute (33%‐43%, P