In a previous study (Place et al. submitted manuscript), we showed that level of fatigue was similar and involved the same mechanisms when sustaining a submaximal isometric contraction at (i) 40% maximal voluntary contraction (MVC) torque (constant-torque task) vs. (ii) an EMG level when exerting 40% MVC torque (constant-EMG task) with the knee extensor muscles until exhaustion. Indeed, we showed comparable reductions in MVC, peak twitch (Pt) and voluntary activation level (VAL) at the end of the two tasks despite a two-fold longer endurance time for the constant-EMG task. The aim of the present study was to clarify the time course of fatigue during the constant-EMG task to elucidate why endurance time is greater for this task.