Children experienced no apparent peripheral fatigue and higher central fatigue than adults. The greater fatigue resistance in children could be related to a strategy of the CNS aimed at limiting the recruitment of motor units to prevent any extensive peripheral fatigue.

IMS is an effective way to propose dynamic muscle strengthening for knee OA rehabilitation and has a significant effect on pain and disability. Because of the weak methodology and the great heterogeneity of studies, particularly in IMS protocol and outcome measures, insufficient data are available to provide guidelines about efficacy and strategy. Future clinical trials are needed, but more attention should be paid to the methods of such studies to clarify the role of IMS in the therapeutic armamentarium of knee OA.

The lower ability of children to fully activate their motor units at long muscle length could account for their lower specific torque because no difference in theoretical specific torque was observed between groups at 90° and 100°.

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). Methods: Nine prepubertal boys (9.9  1.3 yr.), eight male adolescents (13.6  1.3 yr.) and eleven men (23.4  3.0 yr.) 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). Results: 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). Conclusions: 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.

Obese girls fatigue faster than their lean counterparts. The peripheral factors mainly account for fatigue in obese girls, whereas central factors are mainly involved in lean girls.