Which are the best VO2 sampling intervals to characterize low to severe swimming?

Cardiorespiratory response in swimming has been used to better understand aerobic performance, especially by assessing oxygen uptake (VO2). The current study aimed to compare different VO2 time-averaging intervals throughout low to severe swimming intensities, hypothesizing that VO2 values are similar for different time-averages at low-moderate and heavy swimming intensities, but not for the severe domain. Twenty male trained swimmers completed an incremental protocol of 7x200 m until exhaustion (0.05m/s increments and 30s intervals). VO2 was measured by a portable gas analyser connected to a snorkel system. Six time-average intervals (breath-by-breath 5, 10, 15, 20 and 30 s) were compared for all the protocol steps. Breath-by-breath and 5 s average exhibited higher VO2 values than averages ≥10 s for all swimming intensities (P≤0.02; partial η2≤0.28). VO2 values did not differed between 10, 15, 20 and 30 s averages throughout the incremental protocol (P>0.05; partial η2≤0.05). Furthermore, 10 and 15 s averages showed the lowest VO2 mean difference (0.19 mL.kg¯¹.min¯¹). For the six timeaverage intervals analysed, 10 and 15 s averages were those that showed the lowest changes on VO2 values. We recommended the use of 10 and 15 s time-averaging intervals to determine relevant respiratory gas exchange parameters along a large spectrum of swimming intensities.