Impact of the menstrual cycle on critical power and submaximal exercise oxygen uptake in recreationally active, eumenorrheic females

The effects of the menstrual cycle on objective and subjective exercise performance are currently unclear. The current study aimed to investigate differences in critical power (CP) and submaximal exercise oxygen uptake (VO2) across three distinct phases of the menstrual cycle (early follicular, late follicular, and mid luteal) in 12 recreationally active, eumenorrheic females. Menstrual cycle phase was determined using the 3-step method of calendar-based counting, urinary ovulation test strips, and serum hormone analyses. CP and work prime (W’) were assessed during a 3-minute all-out test on a mechanically-braked cycle ergometer. Submaximal VO2 and respiratory exchange ratio (RER) were assessed during 30 minutes of submaximal exercise on a cycle ergometer, with only the final 10 minutes of steady-state exercise data being used for analysis. Subjective rating of perceived exertion (RPE) and affect were assessed at the conclusion of the 3-min all-out test and every 5 minutes during the 30-min submaximal exercise protocol. Participants also completed the Menstrual Distress Questionnaire (MDQ) during each phase of testing to assess menstrual cycle symptomology. For 3-min all-out testing, CP and W’ did not differ across phases ((F [2, 22] = 1.31, p = 0.29) and (F [1.34, 22] = 0.20, p = 0.74), respectively). Similarly, RPE (x2 [2, 12] = 1.00, p = 0.61) and affect (x2 [2, 12] = 0.21, p = 0.90) did not differ following the 3-min all-out test across phases across phases. For submaximal exercise, VO2 (F [2, 22] = 0.87, p = 0.43) and RER (F [2, 22] = 2.50, p = 0.11) were not different across menstrual cycle phases. However, RPE was different across phases (x2 [2, 12] = 10.09, p = 0.01), with post-hoc tests indicating lower RPE during the late follicular phase (11 ± 1) versus the early follicular (13 ± 2; p = 0.01) and mid luteal phases (13 ± 2; p = 0.06). Similarly, total MDQ scores were lower during the late follicular phase (61 ± 12) versus the early follicular v (76 ± 21; p = 0.02) and mid luteal phases (75 ± 20; p = 0.01). Furthermore, there were differences in subscales of pain, water retention, and negative affect across phases, with post-hoc analyses indicating lower scores for each of these subscales during the late follicular phase compared to the early follicular and mid luteal phases (p < 0.05, all comparisons). These findings indicate that objective exercise performance does not differ across the menstrual cycle. In contrast, subjective submaximal exercise performance (specifically perceived exertion, pain, negative affect, and water retention) may differ across the menstrual cycle – with the late follicular phase having the lowest symptomology and best threshold for pain. For practical application, these findings suggest that exercise prescription/training should not differ across the menstrual cycle and individuals should instead focus on the management of symptomology.