Repeated sprint in hypoxia as a time-metabolic efficient strategy to improve physical fitness of obese women

Abstract

Purpose: To investigate the training and detraining effects of two different hypoxic high-intensity protocols on cardiorespiratory fitness, maximal fat oxidation and energy contribution in obese women.

Methods: 82 obese women completed a 12-week training of: (1) interval training in hypoxia (IHT; n = 19; 3 min at 90%W_max: 3 min at 55-65%W_max; FiO₂ = 17.2%), (2) interval training in normoxia (INT; n = 20; 3 min at 90%W_max: 3 min at 55-65%W_max), (3) repeated sprint training in hypoxia (RSH; n = 22; 30 s at 130%W_max: 3 min at 55-65%W_max; FiO₂ = 17.2%), and (4) repeated sprint training in normoxia (RSN; n = 21; 30 s at 130%W_max: 3 min at 55-65%W_max). VO_2max, workload, time to exhaustion and heart rate were assessed at baseline, after completion of 36 training sessions over 12 weeks and after 4 weeks of detraining.

Results: Hypoxic training (IHT and RSH) showed a significant positive effect on absolute (p < 0.001) and relative maximal oxygen uptake (p < 0.001) as well as VT2 (%VO_2max; p < 0.001). Both IHT and RSH showed significantly higher values of absolute VO_2max (IHT: + 26.63%; RSH: + 19.79%) and relative VO_2max (IHT: + 27.95%; RSH: + 19.94%) between baseline and post-exercise (p < 0.001). VO_2max (IHT: + 21.74%; RSH: + 17.65%) and relative VO_2max (IHT: + 23.53%; RSH: + 17.15%) remained significantly higher after detraining in IHT and RSH (p < 0.001).

Conclusion: A larger improvement in cardiorespiratory fitness has been observed after high-intensity interval training under normobaric hypoxia. As interval training or repeated sprint training did not show a significant effect, RSH might provide a time-metabolic effective strategy in this population.

Keywords: Cardiometabolic health; Exercise cessation; Intensity exercise; Normobaric hypoxia; Obesity.