Acute performance responses to repeated treadmill sprints in hypoxia with varying inspired oxygen fractions, exercise-to-recovery ratios and recovery modalities

Purpose For optimizing the quality of repeated-sprint training in hypoxia, the differences in the acute performance responses to a single session of repeated-sprint exercise with various (i) inspired oxygen fractions; (ii) exercise-to-recovery (E:R) ratios and (iii) recovery modalities were examined. Methods Ten male participants performed three sets, 5 x 5-s all-out treadmill sprints, E:R ratio of 1:5, passive recovery, in seven trials randomly. In four of the seven trials, hypoxic levels were set corresponding to sea level (SL1:5P), 1500 (1.5K(1:5P)), 2500 (2.5K(1:5P)), and 3500 m (3.5K(1:5P)), respectively. In a further two trials, the hypoxic level of 3.5K(1:5P) was maintained, while the E:R ratio was reduced to 1:4 (3.5K(1:4P)) and 1:3 (3.5K(1:3P)), respectively. In the last trial, the passive recovery mode of 3.5K(1:5P) was changed to active (3.5K(1:5A)). Results In comparison to SL1:5P, the averaged peak velocity (P-Vel), mean velocity (M-Vel), and velocity decrement score (Sdec) of the sprints, and the cumulative HR-based training impulse (cTRIMP) in 1.5K(1:5P) and 2.5K(1:5P) were well maintained. Minor decrement in the M-Vel was found in 3.5K(1:5P.) Conversely, lowered E:R ratio in 3.5K(1:4P) and 3.5K(1:3P) significantly reduced the P-Vel (>= -2.3%, Cohen's d >= 0.43) and M-Vel (>= -2.4%, >= 0.49), and in 3.5K(1:3P) altered the Sdec (107%, >= 0.96), and cTRIMP (-16%, 1.39), when compared to 3.5K(1:5P). Furthermore, mild reductions in M-Vel (-2.6%, 0.5) was observed in 3.5K(1:5A) using the active recovery mode. Other variables did not change. Conclusion The findings suggest that a 3.5K(1:5P) marginally maintained sea-level training loads, and as a result, could maximally optimize the training stress of hypoxia.

Automated summary

The study found that 3.5K(1:5P) marginally maintained sea-level training loads, maximizing the training stress of hypoxia.