Étude par SRM P 31 des effets de l’âge sur la capacité oxydative musculaire

Abstract

Purpose To investigate in vivo comparatively and noninvasively skeletal muscle oxidative capacity from the measurement of PCr resynthesis rates during the post-exercise recovery period in children and adults, using 31-phosphorus magnetic resonance spectroscopy. Method Seven prepubertal boys and 10 men performed finger flexions at a frequency of 0.7 Hz against a weight adjusted to 15% of the maximal voluntary contraction for 3 min. Skeletal muscle oxidative capacity was measured during the 15-min post-exercise recovery period from the rate constant of PCr ( k PCr) time-dependent changes and from the inferred maximum aerobic rate of ATP production ( V max). Results End-of-exercise pH was not significantly different between children and adults (6.6 ± 0.2 versus 6.5 ± 0.2) indicating that indices of PCr recovery kinetics ( k PCr and V max) can be reliably compared. The k PCr and V max values were about twofold higher in young boys as compared to men ( k PCr: 1.7 ± 1.2 versus 0.7 ± 0.2 min −1; V max: 49.7 ± 24.6 versus 29.4 ± 7.9 mM min −1, P < 0.05). Conclusion The results of the present study clearly illustrate a greater mitochondrial oxidative capacity in young children.