Author: paloma

05 abr Retested yearly for 3 years, the boys’ fat oxidation rates occurred at progressively lower percentage of VO

If children indeed employ a lower proportion of type-II motor units during exercise, they should be expected to demonstrate lower carbohydrate and higher fat metabolism. Riddell et al. (79) found that during graded exercise, fat oxidation rates peaked at

VO2 Kinetics

Phase II of the pulmonary VO₂ kinetics, following exercise onset, is thought of as closely reflecting the oxygen uptake kinetics of the working muscles (9). At any relative exercise intensity, faster phase-II kinetics would be expected in individuals with higher relative aerobic power (maxVO₂) (74), muscle oxidative capacity, or type-I muscle-fiber composition (8). If children do not use type-II motor units to the same extent as adults, their muscles would be characterized by higher functional composition of type-I muscle fibers and would be expected to have faster muscle VO₂ kinetics and consequently demonstrate faster phase-II pulmonary VO₂ kinetics. Indeed, in comparison with adults or adolescents of comparable or even somewhat superior aerobic power, children have been repeatedly shown to attain a given percentage of the ultimate VO₂ response faster than adults (38,86,95).

Thus, children's lower lactate response, faster PCr and VO₂ kinetics and greater reliance on fat oxidation provide equivocal support to the differential metabolic profile and differential motor-unit activation hypotheses, as well as to differential muscle composition ( Table 1 ).

Training Response

Following resistance training, children have been shown to proportionately improve their strength to an extent similar to that observed in adults (80,81). However, while strength gains in adults are typically closely tied to muscular hypertrophy, only a limited hypertrophic response has been found in adolescents (64), and none could generally be shown in prepubertal children (see (12,81) for review).