Neuromuscular fatigability differs between prepubertal children and young adults of both sexes – a pilot study

<ns3:p>Background Prepubertal children are generally less fatigable than adults, hypothesized due to lower reliance on fast-twitch muscle fibers. Since prior research suggests females may be more fatigue-resistant than males, this study aimed to examine age and sex differences in neuromuscular fatigability. Methods In this cross-sectional pilot study, twenty-four prepubertal children and thirty-six adults (7-10y; 20-30y, 50%F) performed maximal voluntary isometric contractions (MVC) before and after a failure task at 60%MVC of the knee extensors. Rate of torque development (RTD) was measured within the first 150ms of MVCs. Perceived effort was assessed at task completion. Surface-electromyography was recorded to evaluate changes in root-mean-square (RMS) and median-frequency (MDF) in agonist muscles. Age and sex differences were analyzed using linear mixed models and Cohen’s d effect sizes. Results Children showed greater MVC reduction (d=0.57) with minor sex differences (d≤0.17), while RTD decreased more in adults (d=-0.53) and males (d=0.30). Female children had the shortest time to failure (d=0.95) and lowest perceived effort (d=0.65). Children exhibited higher initial EMG activity but RMS (d≥-0.13 to -0.18) and MDF (d≥0.07-0.14) changes tend to be smaller across time. Conclusion Higher MVC-reduction in children suggests central or cognitive fatigue, whereas other findings support the hypothesis of lower recruitment of larger motor units in children. Further studies should explore sex-specific developmental changes and training implications.</ns3:p>