Effects of Menstrual Cycle Phase on Aerobic Parameters During a Graded-Exercise Test
Abstract
Female participants are underrepresented in exercise research, and this exclusion can largely be attributed to a lack of knowledge regarding impacts of menstrual cycle on exercise. Results from previous exercise studies that have attempted to test different phases of the menstrual cycle often exhibit contrasting methodologies, making them difficult to compare. For maximal aerobic testing, many studies have displayed conflicting evidence about whether or not menstrual cycle phase impacts variables of performance, like VO2max, blood lactate concentration, respiratory exchange ratio (RER), maximal heart rate (HR), and rating of perceived exertion (RPE). Purpose: The purpose of this study was to examine how different phases of the menstrual cycle – menses (bleeding), the ovulatory phase, and the mid-luteal phase – may affect objective and subjective parameters during a graded exercise test (GXT) in a healthy, college-age population. Methods: 21 participants (12 females, 9 males), age 18-24 (mean age = 21.38 ± 1.32 years) were recruited to participate in this study. All participants completed three maximal GXTs using a relative ramp protocol and a 20-minute verification protocol on a cycle ergometer corresponding to specific menstrual cycle phases. Females used the basal body temperature method to track their menstrual cycle and came in for visits during menses (M), ovulation (O), and the mid-luteal phase (L). Visit order was dependent on their current phase at the time of enrollment. Males visit order was randomized and matched for time between visits according to an average 28-day cycle. Results: Though males exhibited significantly higher values for height, maximal load, and absolute and relative VO2max compared to females (p < 0.05), no significant differences were present across the different phases for the objective parameters (height, weight, absolute and relative VO2max, max HR, RER, lactate, time to failure, and maximal load). Males also did not exhibit significant differences for the subjective parameters across visits – overall RPE, localized RPE, and recovery rating. Females, however, displayed significant differences for each subjective variable. Significantly higher values for overall RPE were found during visit M compared to visits O and L (p < 0.05), significantly higher values for localized RPE were found for visit M compared to visit O (p < 0.05), but not visit L, and significantly lower values for recovery rating were found for visit M compared to visit O and visit L (p < 0.001). No significant differences were found between visit O and visit L in the female participants. Conclusion: Females felt like they were exerting more during the GXT and felt less recovered the day following visit M, or menses, compared to the other visits (O and L), while males did not exhibit any significant changes across visits for any of the parameters. More research regarding the cause of this finding is warranted and highly recommended but may be attributed to the drop in sex hormone concentration at this point in the menstrual cycle. Moving forward, exercise researchers should use extreme caution while testing during menses until more knowledge is gained in this area.
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