Sprint interval training (SIT) is usually performed at maximal ‘all-out’ intensities, that are 5-8-times higher than the power needed to elicit VO2peak. However, the %VO2peak associated with repeated submaximal power sprints (%Pmax), particularly when paired with varying rest periods, remains unknown. Investigating the %VO2peak in repeated submaximal power sprints is pivotal, enabling the personalization of workout routines to specific training goals.

PURPOSE: The aim of this study was to systematically investigate the acute physiological responses induced by three levels of %Pmax intensities (50%, 75%, and 100% of Pmax) with three varying rest periods (15, 30, and 45-s) between thirty 4-s sprints. METHODS: Nine healthy (25±4.9), recreationally active participants took part in nine trials, performing thirty 4-s sprints during cycling with inertial loading at three different intensities and rest periods, in randomized order. RESULTS: Power outputs varied across differing intensities and rest periods. At 52±0.7 %Pmax and 74% ±0.3 %Pmax, the average output was constant within the rest periods. However, the ‘all-out’ efforts revealed that 15-s rest elicited a lower (pmax of 88±9.0 %Pmax compared to 95±3.9%, and 96±5.7% of Pmax for 15 vs. 30, and 45-s of rest (p<0.05). VO2 varied (p2peak for 15-s rest; 35±5.8%, 45±10.5%, 66±12.2% VO2peak for 30-s rest; and 28±6.7%, 33±5.7%, 54±9.8% VO2peak for 45-s rest, corresponding to intensities at 52%, 74%, and 88% of Pmax, respectively. Notably, a linear regression model identified the equation for VO2 (mL/min) = 1088.89 + 28.32(%Pmax intensity) - 38.75(rest in s) (R2= 0.91). CONCLUSION: A wide range of VO2 responses (i.e., 28-84% VO2peak) can systematically be elicited by varying the intensity and rest period during repeated 4-s sprints cycling using inertial loading, offering valuable insights for designing personalized training regimens.



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