Purpose: Numerous investigations have reported changes in metabolic and cardiorespiratory responses associated with the menstrual cycle. We examined whether variables commonly used in exercise testing are influenced by menstrual cycle phases. Methods: Nineteen eumenorrheic women performed two incremental tests to voluntary exhaustion on a cycle ergometer during two different phases of the menstrual cycle: the follicular phase (FP) and the luteal phase (LP). Our study variables were power output, VO2, HR, VE, RER, ventilatory equivalents of oxygen (VE/VO2) and carbon dioxide (VE/VCO2), and blood lactate concentration (LA) and were measured at rest, at exhaustion, and at different thresholds of aerobic and anaerobic metabolism. The threshold determination consisted of a three-phase model with two lactate turnpoints (LTP1, LTP2) and a three-phase model with two respiratory thresholds: the anaerobic threshold (AT) and the respiratory compensation point (RCP). Results: When comparing power output, VO2, LA, HR, and RER, we found no significant differences between FP and LP at rest, at maximal load, at any selected threshold, or any stage of the incremental tests. We observed higher values for VE/VO2, VE/VCO2, and VE at rest, at exhaustion, and at our AT in LP. Conclusion: We did not find performance changes associated with menstrual cycle. Our data do not support findings that the menstrual cycle influences lactate "thresholds" and ventilatory "thresholds." In agreement with other studies, we observed a higher ventilatory drive in the LP compared with the FP of the menstrual cycle.
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