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

Abstract

This study examined potential sex differences on performance and perceived fatigability during a whole-body endurance exercise performed under normoxia or moderate hypoxia. Nine male and eight female 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 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) (P = 0.039). There was no effect of sex or condition (P ≥ 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 normoxia for both groups (P = 0.002). In conclusion, moderate hypoxia similarly impairs performance and perceived fatigability development in females and males during a 4-km cycling time-trial.