Abstract
Oxygen uptake () kinetics has been reported to be influenced by the activity mode. However, only few studies have compared O2 kinetics between activities in the same subjects in which they were equally trained. Therefore, this study compared the O2 kinetics response to swimming, arm cranking, and cycling within the same group of subjects within the heavy exercise intensity domain. Ten trained male triathletes (age 23.2 ± 4.5 years; height 180.8 ± 8.3 cm; weight 72.3 ± 6.6 kg) completed an incremental test to exhaustion and a 6-min heavy constant-load test in the three exercise modes in random order. Gas exchange was measured by a breath-by-breath analyzer and the on-transient O2 kinetics was modeled using bi-exponential functions. O2peak was higher in cycling (65.6 ± 4.0 ml·kg−1·min−1) than in arm cranking or swimming (48.7 ± 8.0 and 53.0 ± 6.7 ml·kg−1·min−1; P < 0.01), but the O2 kinetics were slower in swimming (τ1 = 31.7 ± 6.2 s) than in arm cranking (19.3 ± 4.2 s; P = 0.001) and cycling (12.4 ± 3.7 s; P = 0.001). The amplitude of the primary component was lower in both arm cranking and swimming (21.9 ± 4.7 and 28.4 ± 5.1 ml·kg−1·min−1) compared with cycling (39.4 ± 4.1 ml·kg−1·min−1; P = 0.001). Although the gain of the primary component was higher in arm cranking compared with cycling (15.3 ± 4.2 and 10.7 ± 1.3 ml·min−1·W−1; P = 0.02), the slow component amplitude, in both absolute and relative terms, did not differ between exercise modes. The slower O2 kinetics during heavy-intensity swimming is exercise-mode dependent. Besides differences in muscle mass and greater type II muscle fibers recruitment, the horizontal position adopted and the involvement of trunk and lower-body stabilizing muscles could be additional mechanisms that explain the differences between exercise modalities.
Highlights
Muscular exercise requires large changes in the metabolic rate often exceeding 10-fold the resting steady-state values (Poole and Jones, 2012)
Extending the V O2 kinetics analysis beyond the V O2 slow component (V O2sc) phase with triathletes, Caputo and Denadai (2004) concluded that the time constant of the fast component phase during running and cycle exercise tests performed at maximal oxygen consumption (V O2max) intensity were independent of the exercise mode performed, but dependent on the training status of the subjects These data suggest that the mechanical differences between cycling and running modes do not influence the time constant in the severe domain, contrarily to the V O2sc
The purpose of this study was to compare the on-V O2 kinetic response during swimming, arm cranking and cycling within the same group of trained triathletes when exercising within the heavy intensity domain
Summary
Muscular exercise requires large changes in the metabolic rate often exceeding 10-fold the resting steady-state values (Poole and Jones, 2012). A rapid and exponential increase in V O2, with a time constant between ∼20–45 s, occurs (Phase II—primary or fast component), in which pulmonary V O2 kinetics largely reflect the kinetics of O2 consumption in the exercising muscles (Grassi et al, 1996) This transitory phase, prior to the achievement of any steady state (moderate intensity) or prior to the development of the slow component phase (heavy and severe intensities), provides a window into the fundamental processes of muscle energetics and metabolic control that are otherwise not accessible (Poole and Jones, 2012). Extending the V O2 kinetics analysis beyond the V O2sc phase with triathletes, Caputo and Denadai (2004) concluded that the time constant of the fast component phase during running and cycle exercise tests performed at maximal oxygen consumption (V O2max) intensity were independent of the exercise mode performed, but dependent on the training status of the subjects These data suggest that the mechanical differences between cycling and running modes do not influence the time constant in the severe domain, contrarily to the V O2sc
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