The menstrual cycle impact on physiological determinants important for endurance performance: Prospective cohort study

Abstract

Purpose: The current study aimed to investigate the fluctuations of menstrual cycle (MC) phase on physiological determinants important for endurance performance. We hypothesized that time to exhaustion, lactate threshold and maximal oxygen consumption (VO2max) would be unchanged across the MC. Additionally, we hypothesized that the oxygen carrying capacity of the blood measured as blood volume (BV), plasma volume (PV) and hemoglobin mass (Hbmass) would change across the MC phases.

Methods: 18 eumenorrheic national level female cross-country skiers and biathletes were recruited for the present study. Six of them completed the entire test protocol, consisting of a familiarization session and three test days during three different hormonal phases (early follicular (EF), late follicular (LF) and mid luteal (ML)) of the MC. One test day consisted of blood sampling, physical testing and measurements of Hbmass with further calculations of BV and PV from carbon monoxide rebreathing method. The physical tests consisted of a lactate profile on treadmill, 5*counter movement jumps, 30 seconds all-out on SkiErg and a treadmill running VO2max-test with time to exhaustion.

Results: BV was significantly higher in LF phase compared to EF phase (5142,5 ± 376,5 vs 4922,6 ± 321,6 mL, P<0.05). There was no significant difference in PV and Hbmass between EF-, LF-, and ML phase. Time to exhaustion, relative VO2max and lactate threshold at blood concentration of 4 mmol*L-1 remained constant throughout the MC. However, absolute VO2max was significantly higher in EF phase compared to ML phase (3481,9 ± 144,4 vs 3438,7 ± 140,5 L*min-1, P<0.05).

Conclusion: These data show that the BV in the EF phase is reduced compared to LF phase. In spite of reduced BV, the overall conclusion confirms that short term endurance performance is not affected by the fluctuations in the ovarian hormones across the MC.