Effect of menstrual cycle phase on exercise performance of high-altitude native women at 3600 m

At sea level normally menstruating women show increased ventilation (V̇E) and hemodynamic changes due to increased progesterone (P) and estrogen (E2) levels during the mid-luteal (L) compared to the mid-follicular (F) phase of the ovarian cycle. Such changes may affect maximal exercise performance. This repeated-measures, randomized study, conducted at 3600m, tests the hypothesis that a P-mediated increase in V̇E increases maximal oxygen consumption (V̇_O2max) during the L phase relative to the F phase in Bolivian women, either born and raised at high altitude (HA), or resident at HA since early childhood. Subjects (N=30) enrolled in the study were aged 27.7±0.7 years (mean ± S.E.M.) and non-pregnant, non-lactating, relatively sedentary residents of La Paz, Bolivia, who were not using hormonal contraceptives. Mean salivary P levels at the time of the exercise tests were 63.3 pg ml^-1 and 22.9 pg ml^-1 for the L and F phases, respectively. Subset analyses of submaximal (N=23) and maximal (N=13) exercise responses were conducted only with women showing increased P levels from F to L and, in the latter case, with those also achieving true V̇_O2max. Submaximal exercise V̇E and ventilatory equivalents were higher in the L phase (P<0.001). P levels were significantly correlated to the submaximal exercise V̇E (r=0.487, P=0.006). Maximal work output (W) was higher (approximately 5 %) during the L phase (P=0.044), but V̇_O2max (1 min^-1) was unchanged (P=0.063). Post-hoc analyses revealed no significant relationship between changes in P levels and changes in V̇_O2max from F to L (P=0.072). In sum, the menstrual cycle phase has relatively modest effects on ventilation, but no effect on V̇_O2max of HA native women.