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

This study aimed to characterise both the kinetics within constant heavy-intensity swimming exercise, and to assess the relationships between 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 , first ventilatory threshold (VT), and the velocity associated with and (2) two square-wave transitions from rest to heavy-intensity exercise, to determine their kinetics. All the tests involved breath-by-breath analysis of freestyle swimming using a swimming snorkel. 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 , and VT, respectively. For the square-wave transition, the time constant of the primary phase (τ p ) 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 (% A ′ sc )]. τ p was correlated with ( r = −0.55, P = 0.01), but not with either ( r = 0.05, ns) or VT ( r = 0.14, ns). The % A ′ sc did not correlate with either ( r = −0.14, ns) or ( r = 0.06, ns), but was inversely related with VT ( r = −0.61, P