Despite acknowledgment of obvious differences in triathlon performance between sexes (study 1), the amount of research exploring female training responses falls far short of that has been done in males.
With a recent growth in the number of women engaging in endurance and ultra-endurance events (study 2) including triathlon (study 1), gaining information on how female hormones affect performance is more important than ever.
Women experience considerable hormonal changes throughout their lifetimes due to the menstrual cycle (MC). Each MC spans approximately 28 days, though this can range between 21-35 days in healthy women (study 3).
The cycle involves cyclical changes in luteinising hormone and follicle stimulating hormone (produced by the pituitary gland) which stimulate the secretion of the sex steroid hormones; oestrogen and progesterone.
Regular menstruation signifies a healthy hormonal milieu for all women of reproductive age, irrespective of how active they are. Disruption in menstruation can therefore be an indication of poor practices in training, nutrition, and/or recovery. In such cases, the individual should seek medical advice to exclude any underlying medical condition.
Fluctuations in sex hormones across the MC allow for the determination of three distinct phases:
1. The follicular phase (before egg release)
2. The ovulatory phase (egg release)
3. The luteal phase (after egg release)
What do female hormones do?
While the primary purpose of the female steroid hormones is to support reproduction, changes in their concentrations over the MC also effect multiple physiological systems, including the cardiorespiratory, thermoregulatory, metabolic, and neuromuscular systems.
In other words, these hormones hugely affect how our body works, including the healthy functioning of the heart, the healthy and weight regulation, body temperature regulation, and the functioning of nerves and muscles.
Oestrogen has anabolic and anti-inflammatory effects and plays a key role in regulating fuel type and availability. Progesterone has anti-oestrogenic effects (ie, those that oppose oestrogen).
Given the importance of these factors in determining the quality of our workout sessions, the influence of the MC on exercise performance is worthy of exploration.
How does the menstrual cycle affect performance?
Several large-scaled studies have indicated that biomarkers of exercise performance and recovery may be affected by hormonal fluctuations throughout the MC (study 4, 5, and 6).
The greatest difference appears to be between the early and late follicular phases [roughly during and the week after your period], when oestrogen rises without a concurrent increase in proestrogen. During the early follicular phase, women may be more susceptible to delayed onset of muscle soreness and strength loss (study 5).
Worth noting is that the luteal phase is associated with a slight increase in body temperature, heart rate and ventilation which may lead to higher cardiorespiratory strain (study 3).
Though trivial and unlikely to be of relevance to the recreational-level exerciser, these effects may be important to high end/elite athletes, where podium placement often comes down to the smallest margins.
Thus, tracking the MC could help inform best practices in tapering training/recovery loads, as well as help reconcile potential periods where exercise performance might be reduced.
There’s still work to be done
A couple of caveats and a few words to the wise; Despite research efforts, there is a lack of consensus concerning the effects of different phases of the MC on athletic performance, with many conflicting or ambiguous findings within the literature mainly due to significant differences in research methods and design.
There’s also large variability in hormonal concentrations both within and between women, partly due to the pulsatile secretion [released in bursts rather than constantly] of many of these hormones (study 7).
These factors underscore the challenge of providing generalized guidelines for women in how best to manage exercise in accordance with their MC.
It’s important that adjustments to individual exercise regimes are made on a personalized level (study 4).
- Lepers, R. (2019). Sex Difference in Triathlon Performance. Frontiers in Physiology, 10(JUL), 973. https://doi.org/10.3389/FPHYS.2019.00973
- Scheer, V. (2019). Participation Trends of Ultra Endurance Events. Sports Medicine and Arthroscopy Review, 27(1), 3–7. https://doi.org/10.1097/JSA.0000000000000198
- Constantini, NW, Dubnov, G., & Lebrun, CM (2005). The menstrual cycle and sport performance. Clinics in Sports Medicine, 24(2). https://doi.org/10.1016/J.CSM.2005.01.003
- McNulty, KL, Elliott-Sale, KJ, Dolan, E., Swinton, PA, Ansdell, P., Goodall, S., … Hicks, KM (2020). The Effects of Menstrual Cycle Phase on Exercise Performance in Eumenorrheic Women: A Systematic Review and Meta-Analysis. Sports Medicine (Auckland, NZ), 50(10), 1813. https://doi.org/10.1007/S40279-020-01319-3
- Romero-Parra, N., Cupeiro, R., Alfaro-Magallanes, VM, Rael, B., Rubio-Arias, J., Peinado, AB, & Benito, PJ (2021). Exercise-Induced Muscle Damage During the Menstrual Cycle: A Systematic Review and Meta-Analysis. Journal of Strength and Conditioning Research, 35(2), 549–561. https://doi.org/10.1519/JSC.0000000000003878
- Oosthuyse, T., & Bosch, AN (2010). The effect of the menstrual cycle on exercise metabolism: Implications for exercise performance in eumenorrhoeic women. Sports Medicine, 40(3), 207–227. https://doi.org/10.2165/11317090-000000000-00000/FIGURES/TAB2
- Janse De Jonge, XAK (2003). Effects of the menstrual cycle on exercise performance. Sports Medicine (Auckland, NZ), 33(11), 833–851. https://doi.org/10.2165/00007256-200333110-00004
Top image: Unsplash / Malik Skydsgaard