The menstrual cycle. (Almost) all women between the ages of 10-16 and up to the age of 51(1) (on average) have to live with it about 450 times(1). A monthly recurring phenomenon in a healthy female body. Since it is an indispensable part of life, it is important to know what is happening in the body, what is normal and how we learn to deal with it during our training. For ourselves as women, but also for men, as coaches, as partners or as fathers or brothers.
The menstrual cycle is one of the most important biological rhythms in human life
Why does a woman have a menstrual cycle?
The purpose of the menstrual cycle is to prepare the body to fertilize an egg and conceive a child in the womb. On average, a cycle lasts 28 days, the first day of menstruation (bleeding) is considered day 1 of the cycle(1). It's one of the most important biological rhythms in a person's life(2), it's much more than a monthly notification that you're not pregnant. It is one of the most important signals that our endocrine system is healthy.
In this article we look at what phases our cycle goes into, what happens in each phase, how it affects our training and what we can do ourselves. Please note that this applies on women with a natural cycle and not a cycle under the influence of hormones in the form of birth control pills, for example.
Why do I need to know what happens during the menstrual cycle?
It's important to understand the menstrual cycle and what's happening to your body during its different phases, it's affecting how we feel. Repeatedly hearing that you are weak during menstruation can lead to a self-fulfilling prophecy(2), meaning it comes true because you believe it. That's why it's important to know the facts.
Is the menstrual cycle the same for every woman?
It is important to note that every woman is different and that the theory generally applies to you, but the length of the cycle and stages and the symptoms experienced can vary from woman to woman. This is also what makes studying the influence of cycle on training terribly difficult: it has to be averaged(3). Where one woman lies on the couch wrapped in a blanket with a bar of chocolate (cliché 😉) on the 3rd day of her period, the other woman carries out a PR(2.4) on the same day.
Can I still run or exercise during my period?
Yes. No problem. Some women need to adjust their training based on the phase or feeling. How this works and whether it makes sense, read below.
Which phases of the menstrual cycle do we know?
There are 3 phases:
- The follicular phase
- The ovulation phase
- The luteal phase
Sometimes menstruation is considered a separate phase, but it is part of the follicular phase. These phases are based on the functioning of the ovaries(2).
Source (9)
The follicular phase
How long does the follicular phase last:
This phase lasts 1-14 days(1) with an average of 9 days(2)
Which hormones are important in the follicular phase?
- Follicle Stimulating Hormone (FSH)
- estrogen
What happens in the body during the follicular phase:
This phase begins with menstruation, which lasts an average of 3-5 days, but anything between 1 and 8 days is considered normal(1). During menstruation, a woman loses a layer of the uterus that was built up to implant a fertilized egg. If a woman has not become pregnant, this is no longer necessary and will be rejected. On average, 80 milliliters of blood are lost.
The follicles (small sacs in which the egg cell matures) grow under the influence of the hormone FSH (follicle-stimulating hormone). More and more estrogen is secreted from the cells surrounding the follicle, this happens when menstruation stops. This starts the production of luteinizing hormone (LH). As estrogen levels continue to rise, LH is released and ovulation occurs a day later(2).
How does the follicular phase affect training:
The hormone level in women is at its lowest at this point in the cycle, almost as high as in men. Stacy Sims points out in her book ROAR(4) that women have more strength during this phase and can build more strength during this phase. This is likely because estrogen is an anabolic hormone(6), meaning it helps build tissue in the body. Many women feel their best during this phase of the cycle(5).
Studies cannot yet say with certainty whether more strength can really be built up in this phase compared to other phases. There are studies that confirm this, but just as many that refute it. Further research in this area is needed(3,6).
Some women experience menstrual cramps in the first few days of their cycle(5). This can affect the intensity at which you can or want to exercise.
The risk of injury seems to be higher during this phase. This may be related to decreased reaction time and neuromuscular control during menstruation(2,4). In the second half of this phase, estrogen also causes increased laxity (slackening) of the ligaments. The hormone progesterone has a protective function on the ligaments(2). The risk of injury to the ligaments of, for example, the ankle and knee (anterior cruciate ligament) is therefore higher.
The risk of torn ligaments is greater in the follicular phase
How does the follicular phase affect recovery:
A woman during this phase recovers faster and experiences less pain(4).
What can we do in the follicular phase:
Strength training and higher intensity training. Because estrogen levels are still low during this phase, you burn more sugar and less fat, allowing you to move more intensely(2,4). As the follicular phase progresses and the ovulation phase approaches, adding more sugar to the diet becomes more important(4).
The ovulation phase
How long does the ovulation phase last:
This phase lasts about 5 days, ovulation theoretically always takes place exactly 14 days before menstruation(1,2), but in practice somewhere between the 8th and 25th day(3). When this phase begins depends on how long the follicular phase lasts(5).
Which hormones are important in the ovulation phase?
- Estrogen
- Follicle Stimulating Hormone (FSH)
- Luteinizing Hormone (LH)
What happens during the ovulation phase?
The high estrogen levels lead to an increase in luteinizing hormone (LH), causing the mature egg cell to detach from the follicle. The egg is now ready for fertilization(1).
At the time of ovulation, some women experience pain in their lower abdomen for a few minutes to a few hours(4).
How does the ovulation phase affect training:
The risk of ligament injury mentioned in the follicular phase seems to be highest in this phase(2). Besides that, this phase does not have a major impact on your training.
How does the ovulation phase affect recovery:
This phase also has no particular influence on your recovery.
What can we do during the ovulation phase:
Train normally, if necessary pay attention to activities that put a lot of strain on your ligaments in relation to the increased risk. If you're trying to conceive, take your chances here.
Source: (10)
The luteal phase
How long does the luteal phase last:
This phase lasts 14 days(1).
Which hormones are important in the luteal phase?
- Progesterone
- Estrogen
What happens during the luteal phase:
The corpus luteum, which produces progesterone, prepares the uterus for implantation of the fertilized egg. However, if it turns out that the egg cell is not fertilized, the corpus luteum stops producing progesterone and breaks down. This happens after about 14 days. Progesterone is then no longer produced(1). Due to the sudden drop in hormones, the woman returns to menstruation, after which the whole cycle starts all over again.
How does the luteal phase affect training:
This phase is also called the "high hormone phase", which refers to the high levels of progesterone and estrogen(2) (although estrogen is slightly higher during the ovulation phase).
This is also the phase where PMS (Premenstrual Syndrome) comes into play, about a week before menstruation. This can lead to bloating, abdominal cramps, cravings for certain foods or snacks, mood swings, depression and insomnia(4,5). Sweet cravings, especially classic chocolate, probably stem from poorer sugar absorption under the influence of progesterone(2,4).
While estrogen has an anabolic effect on the muscles, progesterone has a catabolic effect on the muscles, which means that the tissue breaks down faster than it is built(6). This also seems to be the reason for the reduced performance of some women. As already mentioned, this effect has not yet been clearly demonstrated(3,6).
Under the influence of progesterone, body temperature also increases by 0.3-0.5°C (1,2,7). While there is significantly more thermoregulatory stress in the luteal phase (heat is processed less well), the risk of dehydration is lower during long periods of exertion (180 minutes) due to the increase in the fluid-regulating hormone aldosterone. Although body temperature is higher than in the follicular phase during the same exercise, it was still felt to be lower(7). Despite the reduced risk of dehydration, the risk of overheating is even greater as the increased body temperature will push you to the limit more quickly(2).
The risk of injury for ligament injuries is lower in this phase due to the influence of progesterone(2).
How does the luteal phase affect recovery:
Recovery from high-intensity activity appears to be more difficult for the respiratory system during this phase(8). In 30-40% of women with asthma symptoms, these symptoms increase (not always noticeably)(2). This effect can be enhanced when NSAIDs are taken at the same time, for example to reduce abdominal cramps in PMS(2).
This phase also increases heart rate up to 7 beats per minute(2), which affects recovery.
What can we do during the luteal phase:
In this phase, the engine of the woman runs better on fat than on sugar. This ensures that a woman in this phase is better at long, less intense training and competitions. So you benefit from this during an ultramarathon(2). However, the evidence for this is weak. It is important to consume enough sugar through the diet, as the sugar metabolism is more difficult(4).
Important: The absence of menstruation is not normal
Conclusion
During the menstrual cycle, no differences have been found in the different phases in terms of VO2max, lactate threshold or other values that make fitness measurable(2,8). Also, the value of training certain aspects of a sport at a particular stage, such as heavy weights and intense running sessions right after menstruation and/or ovulation and more endurance at the other stages, has not been clearly established(2,8). Every woman is different, every woman reacts differently to the training.
It is much more important to know what happens in which phase and how it affects the woman's body. Personal adjustments can then be made to ensure optimal performance.
And something else:
The absence of menstruation in a natural cycle, unless of course there is pregnancy, is not normal. Menstruation is a signal for a healthy hormone balance. Excessive exercise combined with suboptimal nutrition and/or rest can lead to menstrual loss. This should always be a sign of alertness to the athlete or coach when they perceive such signals. It is then time to see a doctor.
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Literatur:
1. Thiyagarajan DK, Basit H, Jeanmonod R. Physiology, Menstrual Cycle. StatPearls. Published online October 24, 2022. Accessed April 1, 2023. https://www.ncbi.nlm.nih.gov/books/NBK500020/
2. Constantini NW, Dubnov G, Lebrun CM. The menstrual cycle and sport performance. Clin Sports Med. 2005;24(2). doi:10.1016/j.csm.2005.01.003
3. Colenso-Semple LM, D’Souza AC, Elliott-Sale KJ, Phillips SM. Current evidence shows no influence of women’s menstrual cycle phase on acute strength performance or adaptations to resistance exercise training. Front Sports Act Living. 2023;5. doi:10.3389/fspor.2023.1054542
4. Sims ST. ROAR. (Yeager S, ed.). Rondale; 2015.
5. Roche M. How the Menstrual Cycle Impacts Running—and What You Can Do About It - Trail Runner Magazine. Published 2016. Accessed April 1, 2023. https://www.trailrunnermag.com/training/trail-tips-training/menstrual-cycle-impacts-running-can/
6. de Fatima Massulo J, Antonio do Nascimento M, Carvalho de Sá Nolêto D, et al. Influence of the phases of the menstrual cycle on strength capacity in resistance training Influência das fases do ciclo menstrual na capacidade de força no treinamento resistido. International Seven Journal of Health. 2022;(2):66-75. doi:10.56238/isevjhv2n2-002
7. Christison K, Gurney S, Williamson-Reisdorph C, Covington A. Fluid Balance Across the Menstrual Cycle During Exercise in the Heat. UM Graduate Student Research Conference (GradCon). Published online February 24, 2023. Accessed April 1, 2023. https://scholarworks.umt.edu/gsrc/2023/332/2
8. Benito PJ, Alfaro-Magallanes VM, Rael B, et al. Effect of Menstrual Cycle Phase on the Recovery Process of High-Intensity Interval Exercise—A Cross-Sectional Observational Study. Int J Environ Res Public Health. 2023;20(4). doi:10.3390/ijerph20043266
9. Menstruatiecyclus - Wikipedia. Accessed April 2, 2023. https://nl.wikipedia.org/wiki/Menstruatiecyclus
10. McNulty KL, Elliott-Sale KJ, Dolan E, et al. The Effects of Menstrual Cycle Phase on Exercise Performance in Eumenorrheic Women: A Systematic Review and Meta-Analysis. Sports Med. 2020;50(10):1813. doi:10.1007/S40279-020-01319-3
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