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Research Publication: The effect of the menstrual cycle on performance in endurance athletes

I figured what better way to start this blog than with a piece on the publication of my research for my M.S. in high-altitude exercise physiology. I've included a link here, if you would like to read the full study. My manuscript was published on December 5th, 2022 in the International Journal of Research on Exercise Performance (IJREP), and all research was done at Western Colorado University in the High-Altitude Performance (HAP) Lab in Gunnison, Colorado. The purpose of my study was to determine the effect of different phases of the menstrual cycle on performance in endurance athletes as well as the effects on associated blood biomarkers.

As a competitive endurance runner myself, I became interested in the topic of women's health due to my own struggles with it - I could never maintain a regular period when I trained, often skipping periods and menstruating once every six months, if that. Menstruation is often seen as a nuisance, an inconvenience, a pain (which it can be), but these regular monthly cycles are really a woman's secret weapon...They are a direct indicator of our health, especially as athletes. Any changes to the usual menstrual cycle pattern is usually one of the first indicators that something is not right. By tracking our menstrual cycle, we can keep a close eye on how our bodies are responding to our training loads.

The menstrual cycle on average lasts around 23-28 days and is made up of two phases: The follicular phase (days 1-14) and the luteal phase (days 15-28) (Oosthuyse & Busch, 2010). The cycle is driven by sex steroid hormones estrogen, progesterone, follicle stimulating hormone (FSH), and luteinizing hormone (LH), but is massively influenced by the rise and fall of estrogen and progesterone (Hawkins & Matzuk, 2008). The first day of the menstrual cycle is marked by menstruation or "bleeding," and occurs when estrogen and progesterone have both dropped and are at their lowest concentrations. This sudden drop in these hormones triggers the uterus to start contracting and to shed the inner lining that has been built up to prepare for the implantation of an embryo. The actual bleeding phase usually lasts anywhere from 4-7 days with varying heaviness of flow. On day 14 of a 28 day cycle, luteinizing hormone spikes in concentration causing ovulation, or the release of an egg from the ovaries. This marks the transition to the luteal phase from days 15-28, when estrogen and progesterone slowly begin to rise before dropping once again to stimulate the start of the next cycle (Hawkins & Matzuk, 2008).

The hormonal fluctuations that drive the menstrual cycle influence the body in ways other than exclusively menstrual function. Estrogen and progesterone have been known to affect cardiovascular, metabolic, and respiratory functions, which can impact exercise performance. Previous research has shown increases in heart rate, ventilation rate, fat metabolism, glycogen sparing (Williams & Krahenbuhl, 1997; Forsynth & Reilly, 2008; Oosthuyse & Busch, 2010), and delayed onset of lactate accumulation (Forsynth & Reilly, 2008; McCracken et al., 1994; Oosthuyse & Busch, 2010) in response to exercise in the luteal phase as compared to the follicular phase. Furthermore, increased estrogen concentration favors mobilization of fats for fat metabolism while lower levels of estrogen result in the favoring of carbohydrate metabolism (Isacco et al., 2012). Fats are a slow burning fuel, essential for long endurance-based efforts, while carbs are a fast burning fuel, ideal for shorter, high intensity efforts. This explains why the gender gap begins to close as the race distances increase. Women tend to favor fat metabolism while men tend to favor carbohydrates. As most training regimens are modeled after male physiology, female hormonal fluctuations are rarely taken into account when creating a training plan. Being a female endurance athlete myself, and now working with other female endurance athletes, I became curious to investigate how the different phases of the menstrual cycle affect exercise performance in endurance runners.

Some fun pilot testing!

My study cohort consisted of well-trained endurance runners located in the Gunnison valley and followed a two-month long investigative period in which each woman completed a 5k time trial with pre- and post-blood lactate measures, VO2max test, and blood draws to measure estrogen, progesterone, and cortisol levels during each the early follicular phase (when estrogen and progesterone are lowest) and the mid-luteal phase (when estrogen and progesterone collectively rise). Based on prior research, I had hypothesized that performance over these distances and time durations would be enhanced during the early follicular phase as compared to the mid-luteal phase. Due to my limited sample size available, I was unable to find significant results in exercise performance measures. I believe if I had a larger sample size, I would have been much more likely to find a trend in the data.

The carnage after a VO2max test.

I did however find that my participants each exhibited significantly higher resting cortisol concentrations during their early follicular phase as compared to their mid-luteal phase (11.1 ± 1.3 mg/dL vs. 8.8 ± 2.4 mg/dL). Further research into this indicated an interaction of estrogen and progesterone with the hypothalamic-pituitary-adrenal (HPA) axis. The HPA axis is a pathway in the brain that regulates the secretion of cortisol associated with the stress-response. Estrogen affects the HPA axis in antagonistic ways causing either stimulatory or inhibitory effects depending on which receptor the hormone binds to, while progesterone exhibits inhibitory affects by the modulation of a specific neurotransmitter that interacts with the HPA axis (Hamidovic et al., 2020). The combined effects of estrogen and progesterone during the mid-luteal phase therefore may inhibit the the HPA axis, decreasing cortisol release, as was evident in the present study. The association between cortisol concentration throughout the menstrual cycle and exercise performance warrants further research, as cortisol may impact these performance measures as well.

Limited research exists on athletic women's health, though the field is growing. Oftentimes the unique physiology of women is ignored, and blanket rules based off of men's physiology are applied to everyone when it comes to training, racing, nutrition, sleep, etc. In the words of Dr. Stacy Sims, "Women are not small men." We are different. We are powerful. We deserve to be understood. Let's work with our physiology rather than against it, and find out what we are truly capable of.

Thanks so much for the read, and I hope you've gained some new information from this!


Dokumacı, B., & Hazır, T. (2019). Effects of the menstrual cycle on running economy: Oxygen cost versus caloric cost. Research Quarterly for Exercise and Sport, 90(3), 318–326.

Forsyth, J. J., & Reilly, T. (2008). The effect of menstrual cycle on 2000-m rowing ergometry performance. European Journal of Sport Science, 8(6), 351–357.

Hamidovic, A., Karapetyan, K., Serdarevic, F., Choi, S. H., Eisenlohr-Moul, T., & Pinna, G. (2020). Higher circulating cortisol in the follicular vs. luteal phase of the menstrual cycle: A meta-analysis. Frontiers in Endocrinology, 11, 311.

Hawkins, S. M., & Matzuk, M. M. (2008). Menstrual cycle: Basic biology. Ann N Y Acad Sci.

Isacco, L., Duché, P., & Boisseau, N. (2012). Influence of hormonal status on substrate utilization at rest and during exercise in the female population. Sports Medicine, 42(4), 327–342.

McCracken, M., Ainsworth, B., & Hackney, A. C. (1994). Effects of the menstrual cycle phase on the blood lactate responses to exercise. European Journal of Applied Physiology and Occupational Physiology, 69(2), 174–175.

Oosthuyse, T., & Bosch, A. N. (2010). The effect of the menstrual cycle on exercise metabolism. Sports Medicine, 40(3), 207–227.

Thiros, A., Van Guilder, G. P. (2022). The effect of the menstrual cycle on performance in endurance runners. International Journal of Research in Exercise Physiology, 18(1).

Williams, T. J., & Krahenbuhl, G. S. (1997). Menstrual cycle phase and running economy. Medicine and Science in Sports and Exercise, 29(12), 1609–1618.


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