Physiological Responses During High-Intensity Interval Training in Young Swimmers

This study analyzed whether 100- and 200-m interval training (IT) in swimming differed regarding temporal, perceptual, and physiological responses. The IT was performed at maximal aerobic velocity (MAV) until exhaustion and time spent near to maximalVO₂ peak oxygen uptake (⩒O₂peak), total time limit (t_Lim), peak blood lactate [La^-] peak, ⩒O₂ kinetics (⩒O₂K), and rate of perceived exertion (RPE) were compared between protocols. Twelve swimmers (seven males 16.1 ± 1.1 and five females 14.2 ± 1 years) completed a discontinuous incremental step test for the second ventilatory threshold (VT₂), ⩒O₂peak, and MAV assessment. The swimmers subsequently completed two IT protocols at MAV with 100- and 200-m bouts to determine the maximal ⩒O₂ (peak-⩒O₂) and time spent ≥VT₂, 90, and 95% of ⩒O₂peak for the entire protocols (IT₁₀₀ and IT₂₀₀) and during the first 800-m of each protocol (IT_8x100 and IT_4x200). A portable apparatus (K4b²) sampled gas exchange through a snorkel and an underwater led signal controlled the velocity. RPE was also recorded. The Peak-⩒O₂ attained during IT_8x100 and IT_4x200 (57.3 ± 4.9 vs. 57.2 ± 4.6 ml·kg^-1·min^-1) were not different between protocols (p = 0.98) nor to ⩒O₂peak (59.2 ± 4.2 ml·kg^-1·min^-1, p = 0.37). The time constant of ⩒O₂K (24.9 ± 8.4 vs. 25.1 ± 6.3-s, p = 0.67) and [La^-] peak (7.9 ± 3.4 and 8.7 ± 1.5 mmol·L^-1, p = 0.15) also did not differ between IT₁₀₀ and IT₂₀₀. The time spent ≥VT₂, 90, and 95%⩒O₂peak were also not different between IT_8x100 and IT_4x200 (p = 0.93, 0.63, and 1.00, respectively). The RPE for IT_8x100 was lower than that for IT_4x200 (7.62 ± 2 vs. 9.5 ± 0.7, p = 0.01). Both protocols are considered suitable for aerobic power enhancement, since ⩒O₂peak was attained with similar ⩒O₂K and sustained with no differences in t_Lim. However, the fact that only the RPE differed between the IT protocols suggested that coaches should consider that nx100-m/15-s is perceived as less difficult to perform compared with nx200-m/30-s for the first 800-m when managing the best strategy to be implemented for aerobic power training.