Many people turn to exercise as a way to better their health. Yet, without considering the menstrual cycle, it may be much harder for individuals to achieve their health goals. At the same time, having a sense of awareness of the effect of exercise on one’s menstrual health is equally important to overall health. Beyond the positive impact of exercise on menstrual cycles, how do we identify when it is too much?
Current developments in linking hormones and exercise
This relationship, and the importance of it, has been recently recognised and publicized by elite female athletes, Many of them are now tailoring their training to account for changes across the cycle, as well as speaking out about the importance of maintaining menstruation as an athlete (1, 2). However, due to the gender bias involved in both womens’ health research and sport’s science research, this is an understudied area of scientific inquiry that is only just gaining traction (3 to 6). Nevertheless, there is strong support that the HPO Axis - aka, the system that connects our reproductive health to our brain and thus the rest of our body - is modified by exercise (7,8). Here we will explore the main topics that are supported by science thus far.
Losing one’s period - The Female Athlete Triad
The consequence of the relationship between hormones + exercise that is most discussed is the high prevalence of women developing amenorrhea when they exercise at high intensity (9). Amenorrhea is the medical term used to describe the absence of menstruation in women of reproductive age. It is defined as primary amenorrhea for women who do not experience menstrual bleeding by age 15. We define as secondary amenorrhea the cases in which women do not experience a period for three months or longer (10). Research suggests that the predominant cause of this is an energy deficit - meaning one is eating less calories compared to the energy they are expending via exercise (11,12). Highly exercising women are especially prone to developing this issue, leading to the labels of the Female Athlete Triad or Relative Energy Deficiency in Sport (RED-S) (13,14). These terms define the combination of amenorrhea, an energy deficit (burning more calories than you consume) and long term consequences such as low bone density (15,16).
While historically viewed as a problem for athletes alone, all women who restrict their caloric intake and/or exercise rigorously are at risk of developing this (17). Given that menstruation is a vital part of female health, the absence of periods can have damaging consequences. Thus, it is important to be cognizant of the potential to develop amenorrhea, as well as to always incorporate proper fuel and rest into one’s fitness routine.
Menstrual cycle, exercise and inflammation
Another way that hormones may change due to exercise is related to inflammation. Many studies demonstrate that exercise may be a useful intervention for menstrual symptoms such as primary dysmenorrhea (PD), PMS, and PMDD(18-23). Cascading hormonal changes lead to an increase of estrogen, dopamine, endorphins, and endogenous opiate peptides, which create a 'feel good' sensation. There is also evidence that exercise may suppress prostaglandins, which are the pesky fatty acids which are often responsible for menstrual discomfort (24,25).
However, as with all things, one can have too much of a good thing. Exercise is inherently inflammatory and too much may actually make menstrual symptoms worse (29). How often, how hard, and how long to exercise varies from individual to individual, so having a relationship with your body is crucial to finding the right balance for you.
Exercising across the menstrual cycle
As hormones change across the cycle, the way our body responds to exercise does too. While this is the most understudied area of research, there is much to interpret from how we understand the menstrual cycle. During the first week, female sex hormones are low while testosterone is relatively high, potentially making one prone to strength training and spacial skills (30,31). Around ovulation, our energy levels and pain thresholds are high, creating a great time to push training to the limit (32 to 34). In the second two weeks, as our temperatures rise with ovulation, our appetite increases, and symptoms kick in, exercising in heat, without proper fuel, or in conjunction with symptoms may be more difficult (35, 36). Nevertheless, by having an approach to training that involves a relationship with one’s body and one’s cycle, one can 'train up' on their body and be able to exercise and perform throughout the entire menstrual cycle.
Key takeaway
Exercise is a tool for increasing one’s health. Yet, without considering menstrual health, one may not be able to achieve this goal as effectively, or may even engage in activities that inhibit this result. Taking female physiology into account is a way to empower women to achieve their intended outcome and lead their healthiest lives. Assessing exercise through the lens of the menstrual cycle can reinforce the idea of exercising to become your healthiest self, rather than to fit a certain societal expectation. A strong case for the value of radical self-knowledge.
