S. Zanconato et al., P-31-MAGNETIC RESONANCE SPECTROSCOPY OF LEG MUSCLE METABOLISM DURING EXERCISE IN CHILDREN AND ADULTS, Journal of applied physiology, 74(5), 1993, pp. 2214-2218
Gas exchange response to high-intensity exercise differs in children a
nd adults. We hypothesized that these findings are related to a lower
anerobic ATP supply in children. We predicted therefore a maturation o
f muscle high-energy phosphate metabolism during exercise. To test thi
s hypothesis, we measured calf muscle P(i), phosphocreatine (PCr), and
pH with P-31-nuclear magnetic resonance spectroscopy during rest and
progressive exercise in 10 children and 8 adults. No differences were
found at rest in pH and P(i)/PCr between children and adults. Exercise
resulted in a greater increase in P(i)/PCr (P < 0.001) and decrease i
n pH (P < 0.0001) in adults than in children. Six adults and five chil
dren exhibited a transition from a slow to a faster rate of P(i)/PCr i
ncrease and pH decrease during exercise. No significant differences we
re found between the two groups in the initial slow-phase slopes of P(
i)/PCr and pH as a function of work rate. In contrast, during the fast
phase, P(i)/PCr increased (slope: adults 23.6 +/- 9.8, children 10.7
+/- 2.5; P < 0.05) and pH decreased (slope: adults -6.0 +/- 1.9, child
ren -3.7 +/- 1.2; P < 0.05) more rapidly in adults than in children. I
n conclusion, high-intensity exercise results in different kinetics of
P(i)/PCr and pH between children and adults. These results suggest th
at children are less able than adults to affect ATP rephosphorylation
by anaerobic metabolic pathways during high-intensity exercise.