Exercise ventilation: Effects of menstrual cycle

The purpose of this study was to compare the breathing responses at rest and during incremental exercise in both the follicular and luteal phases of the menstrual cycle in healthy females that reported a normal menstrual cycle and were not using birth control medications. Subjects were healthy females that were 20-25 years old with no known history of cardiopulmonary, metabolic, or musculoskeletal disease who freely volunteered to participate in the study. All subjects reported a normal menstrual cycle during the previous 4 months and were not currently using birth control medications as determined from the medical/menstrual history form. Standard pulmonary function testing (FVC, FEV1, PF, and FEF) was performed to demonstrate normal lung function at rest. Next, an incremental graded exercise test (GXT) was conducted on a cycle ergometer. Furthermore, the subjects performed a maximal inspiratory pressure (MIP) maneuver before and immediately following the GXT. Maximal flow rates and capacities (spirometry) showed no significant differences (p > 0.05) in the follicular and luteal phases. The results indicated no significant differences (p > 0.05) in resting, submaximal, and maximal VE across the menstrual cycle. The ventilatory equivalents, VE/VO2 and VE/VCO2, showed no significant differences (p > 0.05) across the menstrual cycle. No significant differences within or between conditions (p > 0.05) were found in MIP before and after exercise. In conclusion, these results suggest that menstrual cycle hormones did not affect breathing responses at rest, submaximal, and maximal exercise. Additionally, there are no differences in maximal exercise test variables between the follicular and luteal phases of the menstrual cycle.