VO₂ at maximal and supramaximal intensities: Lessons to high-intensity interval training in swimming

Purpose: To establish appropriate work intensity for interval training that would elicit maximal oxygen uptake (VO₂max) for well-trained swimmers. Methods: Twelve male competitive swimmers completed an incremental protocol to determine the minimum velocity at VO₂max (vVO₂max) and, in randomized order, 3 square-wave exercises from rest to 95%, 100%, and 105% of vVO₂max. Temporal aspects of the VO₂ response were examined in these latter. Results: Swimming at 105% of vVO₂max took less (P < .04) absolute time to achieve 90%, 95%, and 100% of VO₂max intensities (35.0 ± 7.7, 58.3 ± 15.9, 58.3 ± 19.3 s) compared with 95% (72.1 ± 34.3, 106.7 ± 43.9, 151.1 ± 52.4 s) and 100% (55.8 ± 24.5, 84.2 ± 35.4, 95.6 ± 29.8 s) of VO₂max. However, swimming at 95% of vVO₂max resulted in longer absolute time (P < .001) at or above the desired intensities (90%: 268.3 ± 72.5 s; 95%: 233.8 ± 74.3 s; 100%: 173.6 ± 78.2 s) and more relative time at or above 95% of VO₂max than 105% of vVO₂max (68.6% ± 13.5% vs 55.3% ± 11.5%, P < .03), and at or above 100% of VO₂max than 100% and 105% of vVO₂max (52.7% ± 16.3% vs 28.2% ± 10.5% and 34.0% ± 11.3%, P < .001). At 60 s of effort, swimmers achieved 85.8% ± 11.2%, 88.3% ± 5.9%, and 94.7% ± 5.5% of the VO₂max when swimming at 95%, 100%, and 105% of vVO₂max, respectively. Conclusions: When training to elicit VO₂max, using higher swimming intensities will promote a faster VO₂ response but a shorter time spent above these intensities. However, lower intensities allow maintaining the desired response for a longer period of time. Moreover, using the 60-s time period seem to be a more adequate stimulus than shorter ones (~30-s), especially when performed at 105% of vVO₂max intensity.