Exercise V˙eand physical performance at altitude are not affected by menstrual cycle phase

We hypothesized that progesterone-mediated ventilatory stimulation during the midluteal phase of the menstrual cycle would increase exercise minute ventilation (V˙e; l/min) at sea level (SL) and with acute altitude (AA) exposure but would only increase arterial O₂ saturation (${\text{Sa}}_{O_2}$ , %) with AA exposure. We further hypothesized that an increased exercise${\text{Sa}}_{O_2}$ with AA exposure would enhance O₂ transport and improve both peak O₂ uptake (V˙o_{2 peak}; ml ⋅ kg⁻¹ ⋅ min⁻¹) and submaximal exercise time to exhaustion (Exh; min) in the midluteal phase. Eight female lowlanders [33 ± 3 (mean ± SD) yr, 58 ± 6 kg] completed aV˙o_{2 peak} and Exh test at 70% of their altitude-specificV˙o_{2 peak} at SL and with AA exposure to 4,300 m in a hypobaric chamber (446 mmHg) in their early follicular and midluteal phases. Progesterone levels increased (P < 0.05) ∼20-fold from the early follicular to midluteal phase at SL and AA. PeakV˙e (101 ± 17) and submaximalV˙e (55 ± 9) were not affected by cycle phase or altitude. Submaximal${\text{Sa}}_{O_2}$ did not differ between cycle phases at SL, but it was 3% higher during the midluteal phase with AA exposure. NeitherV˙o_{2 peak} nor Exh time was affected by cycle phase at SL or AA. We conclude that, despite significantly increased progesterone levels in the midluteal phase, exercise V˙e is not increased at SL or AA. Moreover, neither maximal nor submaximal exercise performance is affected by menstrual cycle phase at SL or AA.