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

Abstract

Previous studies have demonstrated faster pulmonary oxygen uptake ($\dot{V}{\text{O}}_{2}$) 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 $\dot{V}{\text{O}}_{2}$ kinetics in trained and untrained male adolescents during recovery from moderate-intensity exercise. 15 trained (15 ± 0.8 years, $\dot{V}{\text{O}}_{2\max}$ 54.9 ± 6.4 mL kg⁻¹ min⁻¹) and 8 untrained (15 ± 0.5 years, $\dot{V}{\text{O}}_{2\max }$ 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; $\dot{V}{\text{O}}_{2}$ (breath-by-breath) and muscle deoxyhaemoglobin (near-infrared spectroscopy) were measured continuously. The time constant of the fundamental phase of $\dot{V}{\text{O}}_{2}$ 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. $\dot{V}{\text{O}}_{2}$ 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.