The menstrual cycle minimally affects cardiorespiratory function and body balance control in trained women during acute hypobaric hypoxia exposure (4000 m).

Purpose: The impact of the menstrual cycle (MC) on physical performance has been a hot topic in recent years, due to the increasing professionalisation of women's sports. This study set out to investigate the impact of the MC on the performance of women athletes in a hypoxic environment. The study focused on cardiovascular responses, respiratory function, and postural control as key indicators of sports performance.

Methods: We measured the physiological responses in 20 participants under hypobaric hypoxia (HH) conditions, on two occasions: during the early follicular phase (F) and in the mid-luteal phase (L). Spirometry and postural control parameters at rest were evaluated at sea level and 4000 m simulated altitude in a hypobaric chamber. The exercise performed at hypoxia was divided into two phases of different workload intensities: 40% and 70% of their theoretical maximal rate of oxygen consumption ( ${\dot{\text{V}}\text{O}}_2\text{max}$ ), followed by a recovery period.

Results: Tidal volume (VT) significantly decreased at the L phase compared to the F during high intensity exercise (1.69 vs. 1.82, p ≤ 0.05) and arterial oxygen saturation (SaO₂) was greater in the L phase versus F independently of the exercise intensity (p ≤ 0.01) under hypoxic conditions. Meanwhile, spirometry and other cardiorespiratory responses did not change across the MC. Lateral velocity increased in the L phase with eyes open compared to F (4.88 vs. 4.24, p ≤ 0.05). No significant differences in the performance metrics evaluated between the menstrual cycle phases or between exercise intensities were detected.

Conclusion: Our data confirms that the menstrual cycle in women does not generate sufficiently marked alterations to affect sports performance when acutely exposed to high altitudes.