Background:Children are reported to be more resistant to fatigue than adults, but the metabolic mechanisms are unknown. Although it has been suggested that there are changes in metabolism during puberty, studies to elucidate this have been limited by invasive muscle biopsies. 31P-MRS (Magnetic Resonance Spectroscopy) technology, however, is noninvasive and can be used to quantify the different contributions of oxidative and anaerobic processes to energy expenditure.

Hypothesis/purpose of study:To investigate whether growth and maturation affect muscle energetics in light of reports that resistance to fatigue is greater before puberty.

Subjects:7 prepubescent boys (11.7 ± 0.6 yr) and 10 men (35.6 ± 7.8 yr)

Experimental design: Observational

Treatments and protocol:Each subject performed dynamic finger flexions at 0.7 Hz against a weight adjusted to 15% of their pre-determined maximal voluntary strength for 3 minutes, followed by a 15-minute recovery period. 31P-MRS spectra were used to calculate muscle energetics (adenosine triphosphate synthesis, energy turnover, and oxidative phosphorylation).