No sex differences in performance and perceived fatigability during a self-paced endurance exercise performed under moderate hypoxia.

This study examined potential sex differences in performance and perceived fatigability during a whole body endurance exercise performed under normoxia or moderate hypoxia. Nine males and eight females cyclists performed a 4-km cycling time trial under normoxia or hypoxia conditions. Performance fatigability and its central and peripheral determinants were measured via pre- to post-exercise changes in maximal voluntary isometric contraction (IMVC), voluntary activation (VA), and potentiated twitch force (TwPt) of knee extensors, respectively. Perceived fatigability was characterized via a rating of perceived exertion (RPE). Time to complete the trial was longer in hypoxia than normoxia in females (482 ± 24 vs. 465 ± 21 s) and males (433 ± 30 vs. 408 ± 31 s) ( = 0.039). There was no effect of sex or condition ( ≥ 0.370) for the magnitude of decrease in IMVC (female: normoxia = -14.3 ± 4.4%, hypoxia = -11.8 ± 5.2% vs. male: normoxia = -13.1 ± 9.4%, hypoxia = -12.9 ± 9.8%), TwPt (female: normoxia = -34.4 ± 11.4%, hypoxia = -31.8 ± 18.9% vs. male: normoxia = -30.5 ± 17.9%, hypoxia = -31.9 ± 20.9%), and VA (female: normoxia = -0.5 ± 2.3%, hypoxia = -1.6 ± 1.6% vs. male: normoxia = 0.8 ± 2.2%, hypoxia = -0.5 ± 1.3%). RPE was higher in hypoxia than in normoxia for both groups ( = 0.002). In conclusion, moderate hypoxia similarly impairs performance and perceived fatigability development in females and males during a 4-km cycling time trial. In this study, we showed that females and males develop a similar hypoxia-induced impairment in endurance performance, perceived and performance fatigability during a 4-km cycling time trial. These novel findings indicate that females and males regulate their power output similarly during a 4-km cycling time trial under moderate hypoxia, likely to avoid prematurely exacerbating metabolic disturbances and thereby reaching comparable levels of performance fatigability by the end of the task.