Pulmonary oxygen uptake and muscle deoxygenation kinetics during recovery in trained and untrained male adolescents.

Previous studies have demonstrated faster pulmonary oxygen uptake (VO2) kinetics in the trained state during the transition to and from moderate-intensity exercise in adults. Whilst a similar effect of training status has previously been observed during the on-transition in adolescents, whether this is also observed during recovery from exercise is presently unknown. The aim of the present study was therefore to examine VO2 kinetics in trained and untrained male adolescents during recovery from moderate-intensity exercise. 15 trained (15 ± 0.8 years, VO2max 54.9 ± 6.4 mL kg(-1) min(-1)) and 8 untrained (15 ± 0.5 years, VO2max 44.0 ± 4.6 mL kg(-1) min(-1)) male adolescents performed two 6-min exercise off-transitions to 10 W from a preceding "baseline" of exercise at a workload equivalent to 80% lactate threshold; VO2 (breath-by-breath) and muscle deoxyhaemoglobin (near-infrared spectroscopy) were measured continuously. The time constant of the fundamental phase of VO2 off-kinetics was not different between trained and untrained (trained 27.8 ± 5.9 s vs. untrained 28.9 ± 7.6 s, P = 0.71). However, the time constant (trained 17.0 ± 7.5 s vs. untrained 32 ± 11 s, P < 0.01) and mean response time (trained 24.2 ± 9.2 s vs. untrained 34 ± 13 s, P = 0.05) of muscle deoxyhaemoglobin off-kinetics was faster in the trained subjects compared to the untrained subjects. VO2 kinetics was unaffected by training status; the faster muscle deoxyhaemoglobin kinetics in the trained subjects thus indicates slower blood flow kinetics during recovery from exercise compared to the untrained subjects.