Post-swim oxygen consumption: assessment methodologies and kinetics analysis.

Objective: This study aimed at comparing different recovery-based methods to assess the highest exercise oxygen uptake value ([Formula: see text]Opeak) when swimming at low-moderate, heavy and severe intensities. Complementarily, the different recovery curve kinetics were analysed.

Approach: Eighteen competitive swimmers performed a 5 × 200 m front crawl intermittent protocol (0.05 m · s increments and 3 min intervals), with respiratory gas exchange being continuously measured breath-by-breath during and post-exercise using a portable gas analyser. The directly determined [Formula: see text]Opeak ([Formula: see text]O) was compared with the values obtained by linear and exponential backward extrapolations (of different intervals) and the recovery curve mathematical modelling.

Main Results: [Formula: see text]O rose with intensity increase: 41.96 ± 6.22, 46.36 ± 6.89 and 50.97 ± 7.28 ml · kg min for low-moderate, heavy and severe swims. Linear and exponential regressions applied to the first 20 s of recovery presented the [Formula: see text]Opeak values closest to [Formula: see text]O at low-moderate (42.80 ± 5.54 vs 42.88 ± 5.58 ml kg min), heavy (47.12 ± 4.91 vs 47.48 ± 5.09 ml kg min) and severe intensity domains (51.24 ± 6.89 vs 53.60 ± 8.54 ml kg · min, respectively; r = 0.5-0.8, p < 0.05). The mono-exponential function was the best fit at low-moderate and heavy intensities, while the bi-exponential function better characterized the severe exercise domain (with a slow component amplitude, time delay and time constant of 6.2 ± 2.3 ml kg min, 116.6 ± 24.3 and 39.9 ± 15.2 s, respectively).

Significance: The backward extrapolation of the first 20 s of recovery is the best method to assess the [Formula: see text]Opeak for a large spectrum of swimming intensities. Complementarily, intensity increases imply different recovery curve kinetics, particularly a mono-exponential behaviour for low-moderate and heavy exertions and a bi-exponential dynamics for severe paces.