Résumé :
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The purpose of this investigation was to determine whether maturation affects the relationship between muscle size and maximal strength and to investigate the reasons accounting for the discrepancies among previous studies. Methods: Maximal isometric handgrip force (Fmax) and forearm muscles size were measured in 14 pre-pubertal boys (11.3 ± 0.8 y.o.), 16 adolescents (13.3 ± 1.4 y.o.) and 16 men (35.4 ± 6.4 y.o.). MRI was used to measure anatomical maximal cross-sectional area (MCSA) and muscle volume (VM). VM was compared with anthropometric measurements of muscle volume (VL). Results: Fmax was linearly correlated with VM (r*=0.90), VL (r*=0.85) and MCSA (r*=0.87). The Fmax/VM ratio did not differ between groups. By contrast, Fmax/VL and Fmax/MCSA were significantly higher in adults than in children and adolescents. Additionally, VM was strongly correlated to VL (r*=0.90). This relationship demonstrated that, when compared to MRI, anthropometric measurements lead to a systematic overestimation of muscle volume which was significantly larger in children and adolescents than in adults (43.1 %, 38.5 % and 20.5 % p< 0.05 respectively). Conclusion: Our results showed that the maximal isometric strength which can be exerted by the forearm human muscles is proportional to its size whatever the age. During growth VM was the best index of muscle size. We suggest that the previously reported increased ability to produce maximal strength from childhood to adulthood could be explained by systematic bias introduced by the method used in order to characterize muscle size and not by physiological or neural changes.
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