Purpose The aim of the present study was to investigate the role of central and peripheral factors in neuromuscular fatigue induced by repeated maximal contractions in children and adults.Methods Eleven boys (9.9 1.2 yr) and 12 men (23.9 3.5 yr) completed a fatigue protocol consisting in a repetition of 5-s maximal isometric voluntary contractions (MVC) of the knee extensors separated by 5-s passive recovery periods until the generated torque reached 60% of its initial value. Single magnetic stimulations were delivered to the femoral nerve every five MVC to follow the course of voluntary activation level and the amplitude of the potentiated twitch torque (Qtw(pot)) and vastus lateralis and rectus femoris concomitant M-waves (M-max).Results Torque reached 60% of initial value after 49.5 +/- 16.8 and 34.0 +/- 19.6 repetitions in boys and men, respectively (P