Physiologic and mechanical responses to clustered vs. traditional sprint interval exercise approaches.

Purpose: This study compared responses to a traditional 30-s all-out sprint interval exercise (SIE) session, compared to two SIE sessions divided into clusters, with the aim to assess which of these sessions would result in higher peak oxygen uptake ( $\dot{\text{V}}$ O_2peak), longer time at $\dot{\text{V}}$ O₂ ≥ respiratory compensation point (RCP), and greater peak power output during SIE (PPO_SIE).

Methods: Twelve trained males (19 ± 1 years; 176 ± 5 cm; 65.9 ± 6 kg; $\dot{\text{V}}$ O_2max: 54.0 ± 6.2 mL kg^-1 min^-1) performed three work-matched all-out cycling SIE sessions with a load of 7.5% body mass: (1) SIE30: 4 repetitions of 30-s work with 240-s recovery; (2) SIE15: 4 repetitions of 15-s work with 15-s recovery, plus 15-s work with 225-s recovery; (3) SIE10: 4 repetitions of 10-s work with 10-s recovery, plus 10-s work and 10-s recovery, plus 10-s work with 220-s recovery.

Results: PPO_SIE for SIE30 (697 ± 71 W) was lower than for SIE15 (732 ± 63 W; p = 0.001) and SIE10 (752 ± 75 W; p = 0.001). $\dot{\text{V}}$ O_2peak response for SIE30 (46.5 ± 6.6 mL kg^-1 min^-1) was lower than for SIE15 (51.9 ± 4.8 mL kg^-1 min^-1; p = 0.04) and SIE10 (50.9 ± 5.6 mL kg^-1 min^-1; p = 0.01). Time spent at $\dot{\text{V}}$ O₂ ≥ RCP was shorter for SIE30 (32.9 ± 35.9 s) compared to SIE15 (95.0 ± 52.0 s; p = 0.001) and SIE10 (62.9 ± 46.1 s; p = 0.010). No differences were identified for these variables between SIE15 and SIE10 (p = 0.270).

Conclusion: Compared to the SIE30 session, the clustering-based SIE protocols resulted in higher PPO_SIE values, a greater $\dot{\text{V}}$ O_2peak response, and longer time spent at $\dot{\text{V}}$ O₂ ≥ RCP. Thus, clustering methods can maximize the above-mentioned responses and be appealing alternatives to the traditional 30-s SIE session.