Muscle and cerebral oxygenation during repeated Wingate cycling in hypoxia and normoxia in male middle-distance runners

The effects of acute hypoxia on repeated high-intensity exercise performance and oxygenation kinetics remain unclear. This study examined muscle (vastus lateralis) and cerebral (prefrontal cortex) oxygenation during repeated maximal cycling in hypoxia and normoxia. Ten male middle-distance runners (age: 20 ± 1 y; 800 m season best: 113.3 ± 3.9 s) completed a repeated Wingate protocol (4 × 30 s ‘all out’ efforts with 4-min recovery) under hypoxia (inspired oxygen fraction: 0.145) and normoxia using a randomized crossover design. Mean power output across the four sets was significantly lower in hypoxia than in normoxia (−4.2%, P = 0.007, Cohen’s d = 1.109). During exercise, hypoxia elicited greater muscle deoxygenation and total hemoglobin in the vastus lateralis, alongside lower tissue oxygen saturation in both the vastus lateralis and prefrontal cortex (all P < 0.05). During the 4-min recovery periods, cerebral reoxygenation was greater in normoxia than in hypoxia (P < 0.001), whereas muscle reoxygenation showed only a tendency (P = 0.055). Reductions in power output under hypoxia correlated more strongly with increased cerebral de- and re-oxygenation than with muscle de- and re-oxygenation, both during exercise (r = −0.452 [P = 0.011] vs. r = 0.268 [P = 0.145]) and recovery (r = 0.440 [P = 0.046] vs. r = 0.413 [P = 0.063]). Both muscle and cerebral oxygenation were altered under hypoxia; however, cerebral oxygenation appears more strongly associated with repeated high-intensity exercise performance in hypoxia.