Effects of aerobic fitness on oxygen uptake kinetics in heavy intensity swimming

摘要

This study aimed to characterise both the $ dot{V}{text{O}}_{2} $ kinetics within constant heavy-intensity swimming exercise, and to assess the relationships between $ dot{V}{text{O}}_{2} $ kinetics and other parameters of aerobic fitness, in well-trained swimmers. On separate days, 21 male swimmers completed: (1) an incremental swimming test to determine their maximal oxygen uptake $ (dot{V}{text{O}}_{2max } ) $ , first ventilatory threshold (VT), and the velocity associated with $ dot{V}{text{O}}_{2max } $ $ (vdot{V}{text{O}}_{2max } ) $ and (2) two square-wave transitions from rest to heavy-intensity exercise, to determine their $ dot{V}{text{O}}_{2} $ kinetics. All the tests involved breath-by-breath analysis of freestyle swimming using a swimming snorkel. $ dot{V}{text{O}}_{2} $ kinetics was modelled with two exponential functions. The mean values for the incremental test were 56.0 ± 6.0 ml min−1 kg−1, 1.45 ± 0.08 m s−1; and 42.1 ± 5.7 ml min−1 kg−1 for $ dot{V}{text{O}}_{2max } $ , $ vdot{V}{text{O}}_{2max } $ and VT, respectively. For the square-wave transition, the time constant of the primary phase (τp) averaged 17.3 ± 5.4 s and the relevant slow component (A′sc) averaged 4.8 ± 2.9 ml min−1 kg−1 [representing 8.9% of the end-exercise $ dot{V}{text{O}}_{2} $ (%A′sc)]. τp was correlated with $ vdot{V}{text{O}}_{2max } $ (r = −0.55, P = 0.01), but not with either $ dot{V}{text{O}}_{{ 2 {text{max}}}} $ (r = 0.05, ns) or VT (r = 0.14, ns). The %A′sc did not correlate with either $ dot{V}{text{O}}_{{ 2 {text{max}}}} $ (r = −0.14, ns) or $ vdot{V}{text{O}}_{2max } $ (r = 0.06, ns), but was inversely related with VT (r = −0.61, P 0.01). This study was the first to describe the $ dot{V}{text{O}}_{2}$ kinetics in heavy-intensity swimming using specific swimming exercise and appropriate methods. As has been demonstrated in cycling, faster $ dot{V}{text{O}}_{2} $ kinetics allow higher aerobic power outputs to be attained. The slow component seems to be reduced in swimmers with higher ventilatory thresholds.