Impact of rest interval duration on post-exercise recovery dynamics, ventilatory threshold and respiratory compensation point in endurance athletes: A randomized controlled trial

The primary objective of this study was to investigate the impact of varying rest interval durations in High-Intensity Interval Training (HIIT) on several physiological parameters: Excess Post-Exercise Oxygen Consumption (EPOC), Heart Rate Recovery (HRR), body composition, Ventilatory Threshold (VT) and Respiratory Compensation Point (RCP) in endurance athletes over an 8-week period. The study also aims to identify which of these variables is most sensitive to changes in HIIT rest interval duration.

The study involved a sample of 20 male athletes, with an average age of 21.9 ± 2.61 years, height of 171 ± 4.51 cm, and weight of 63.75 ± 5.11 kg. Participants were divided into two groups (N = 10 per group) and underwent pre-tests before participating in 16 sessions of HIIT with distinct rest protocols: Group 1 had a 2-min active recovery at 70% vOBLA, while Group 2 had a 3-min active recovery at 70% vOBLA. The work interval was 4*8 min (at 80% vVO_2max in weeks 1–4, and 8 interval sessions as 4*4 min in (at 95% vVO_2max) in weeks 5–8. Post-tests were conducted following the training sessions.

Paired t test analysis revealed significant effects (p < 0.05) in all the variables in both groups, except for lean mass and resting heart rate; suggesting a positive adaptation following both the protocols. Analysis of variance (ANOVA) showed no statistically significant differences between the two groups (p > 0.05).

The findings suggest that both HIIT protocols had a significant effect on EPOC, HRR after 2 and 3 min, body composition, VT and RCP over the 8-week period. However, the groups were not different from one another, which means that the shorter rest interval of 2 or 3 min of same intensity works equally on all variables and suggests that efficacy of a HIIT protocol is independent of short rest interval durations (2 or 3 min).

Registration was done prospectively (CTRI No.: CTRI/2021/09/036585); Date—Sept 15, 2021.