Maturation-related changes in the development and etiology of neuromuscular fatigue.

Abstract

The aim of the present study was to investigate the role of maturation on the etiology of neuromuscular fatigue induced by repeated maximal voluntary isometric contractions (MVIC). Nine prepubertal boys (9.9 ± 1.3years), eight male adolescents (13.6 ± 1.3years) and eleven men (23.4 ± 3.0years) performed a series of repeated isometric MVICs of the knee extensors until the MVIC torque reached 60% of its initial value. Magnetic stimulations were delivered to the femoral nerve every five MVICs to follow the course of voluntary activation level (VA) and the potentiated twitch torque (Qtwpot). Task failure was reached after 52.9 ± 12.7, 42.6 ± 12.5, and 26.6 ± 6.3 repetitions in boys, adolescents and men, respectively. VA remained unchanged in men whereas it decreased significantly and similarly in boys and adolescents (p < 0.001). In contrast, Qtwpot remained unchanged in boys and decreased significantly less in adolescents than adults (p < 0.05). Children and adolescents experience less peripheral and more central fatigue than adults. However, adolescents experience more peripheral fatigue than children for a comparable amount of central fatigue. This finding supports the idea that the tolerance of the central nervous system to peripheral fatigue could increase during maturation.