Longitudinal changes in the oxygen uptake kinetic response to heavy-intensity exercise in 14- to 16-year-old boys.

This study examined longitudinal changes in the pulmonary oxygen uptake (pVO(2)) kinetic response to heavy-intensity exercise in 14-16 yr old boys. Fourteen healthy boys (age 14.1 +/- 0.2 yr) completed exercise testing on two occasions with a 2-yr interval. Each participant completed a minimum of three 'step' exercise transitions, from unloaded pedalling to a constant work rate corresponding to 40% of the difference between the pVO(2) at the gas exchange threshold and peak pVO(2) (40% Delta). Over the 2-yr period a significant increase in the phase II time constant (25 +/- 5 vs. 30 +/- 5 s; p = .002, omega(2) = 0.34), the relative amplitude of the pVO(2) slow component (9 +/- 5 vs. 13 +/- 4%; p = .036, omega(2) = 0.14) and the pVO(2) gain at end-exercise (11.6 +/- 0.6 vs. 12.4 +/- 0.7 mL x min(-1) x W(-1); p < .001, omega(2) = 0.42) were observed. These data indicate that the control of oxidative phosphorylation in response to heavy-intensity cycling exercise is age-dependent in teenage boys.