Neuromuscular fatigue differences between prepubertal boys and men after maximal concentric versus eccentric...

This study aimed to compare the neuromuscular fatigue between prepubertal boys and men induced by eccentric and concentric maximal contractions.

Twelve prepubertal boys and twelve men conducted one familiarization and two randomized experimental sessions, including a concentric (CONC) or eccentric (ECC) fatiguing protocol composed of three sets of 30 maximal isokinetic contractions. Maximal voluntary isometric contractions (MVIC) were realized before the fatiguing protocol, after each set, five minutes and one hour after the end of the last set. Measurements included torque and electromyographic activity (EMG) of vastus lateralis (VL) and rectus femoris (RF) muscles during the MVIC and the dynamic contractions of the fatiguing protocol.

A significantly lower decrease of the MVIC torque was observed for boys in comparison to men after the second and third sets of the fatigue protocol (p < 0.001), independently of the modality. Additionally, lower RF EMG during MVIC were observed for boys than for men during the CONC session, while no difference was observed during the ECC session. During dynamic contractions, a lower torque decrease was observed for boys than for men during the whole fatigue exercise in the CONC session (p < 0.001), while no group difference in the ECC session. No age group difference was observed in EMG during the dynamic contractions.

From the present results, boys presented a lower MVIC decrease than men, suggesting lower fatigue regardless of the condition. Thus, the concentric, particularly, and the eccentric solicitations could represent interesting training modalities with prepubertal boys.