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 (V˙O_2peak), longer time at 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; 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). 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 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 V˙O_2peak response, and longer time spent at V˙O₂ ≥ RCP. Thus, clustering methods can maximize the above-mentioned responses and be appealing alternatives to the traditional 30-s SIE session.