Sex influence on the resting physiological responses to different levels of normobaric hypoxia in young, trained population

BACKGROUND: This study investigated the influence of sex on the peripheral oxygen saturation (SpO2) and heart rate (HR) after being exposed to different levels of normobaric hypoxia (NH) at rest. METHODS: Sixty-five trained volunteers (44 males and 21 females) were randomly exposed twice to a low (FiO2=17.4%; 1500 m asl.), moderate (FiO2=15.4%; 2500 m a.s.l.), and severe (FiO2=13.4%; 3500 m a.s.l.) NH with at least 48 hours between them. SpO2 and HR were monitored at baseline and during 25 min of hypoxic exposure at rest. RESULTS: Findings revealed that the female group presented higher SpO2 values at normoxia (ES 0.146; P2 values faster than men at severe altitudes, particularly at 3500 m, despite no HR differences between sexes. These findings suggest that physiological adjustments during NH exposure are different between sexes and should be considered when performing interventions or training sessions in hypoxic conditions.