Repeated Sprint Training in Hypoxia Improves Repeated Sprint Ability to Exhaustion Similarly in Active Males and Females

The aim of this study was to compare the physiological adaptations of males and females to repeated sprint training in hypoxia. Active males and females completed 7 weeks of repeated sprint training in normoxia (RSN, FiO2 = 0.209, males: n = 11, females: n = 8) or hypoxia (RSH, FiO2 = 0.146, males: n = 12, females: n = 10). Before (Pre-) and after (Post-) training, a repeated sprint ability test (RSA) was performed (10 s cycle sprints with 20 s recovery between sprints, until exhaustion), and aerobic and anaerobic qualities were evaluated in normoxia. The number of sprints during RSA increased after training in HYP from 11 to 21 in males and from 8 to 14 in females (p < 0.001, CI = [5, 11]), without significant changes after RSN (10 vs 14 and 8 vs 10 in males and females, respectively). No improvements in mean or peak power output were found in either group. Total work during RSA improved after training in all groups (+9 ± 2 kJ, p < 0.001). Tissue saturation index (TSI) during the repeated sprints was higher in females than males (+10 ± 2 %, p < 0.001). The difference in TSI between the recovery and sprint phases remained unchanged after training. VO2peak during an incremental exercise test increased in all groups (+3 ± 1 ml·kg-1·min-1, p = 0.039). Mean power output during a Wingate test also increased in both males and females in RSN and RSH (+0.38 ± 0.18 W·kg-1, p = 0.036). No changes were observed in hematological parameters after training. Seven weeks of RSH further increased the number of repeated sprints performed to exhaustion compared to RSN in females, in the same order of magnitude as in males.