Period power or wrong, period? The science of athletic performance across the menstrual cycle.

The toilets in the ramshackle, 1970s restrooms at my Midwestern middle school had blessedly long flushes. You could rummage in your bag for a pad, open the plastic wrapper, rip off the adhesive, pull the used pad from your underwear, and deposit it in the metal bin all before the water in the bowl had settled to a hush. No one would be the wiser. Over the summer, though, the school underwent renovation. The new toilets, powerful and efficient, finished their job the moment you depressed the handle. What was a prudish girl to do? The answer: take a friend, someone you trusted with compromising information, to the restroom. Her presence at the sink warned other would-be bathroom users that there was private business afoot; come back later, and don’t look under the stall door to see whose Skechers might give her away.

For anyone raised in a culture of period shame, the news that the US Women’s National Soccer Team is using state-of-the-art systems to track and modify each member’s performance across the menstrual cycle--and going public about the practice in an effort to dispel stigma--could come as a breath of fresh air. After all, as fitness coach Dawn Scott told The Telegraph, “We want to end the taboo. At the elite level, but also for teenage girls. They should feel comfortable talking about this with their coaches.” And if the women who can literally get a stadium to chant “Equal pay” are embracing the science of menstrual cycle variation, shouldn’t the rest of us?
 
As co-fitness coach Dr. Georgie Bruinvels stated of menstrual cycle performance science, “Often we are afraid of discussing this because we don’t really understand it.” I want to argue that exploring the gaps in our understanding is crucial, not only to maximizing the health and achievements of elite athletes and the rest of us, but also to preventing the harms that can—and, in the past, have—come with tying women’s performance to their menstrual cycles. So before we run out and get heart rate monitors, stop watches, and period tracking apps, let’s ask three questions about the science behind the claim that women’s athletic performance varies systematically across the menstrual cycle. Is it true? Is it important—as important as or more important than other factors explaining performance variation? Finally, could this science harm the very people it is intended to help?

Is it true?

Does athletic performance vary systematically across the menstrual cycle? Attempts to quantify changes in athletic performance have yielded mixed results. While Dr. Bruinvels and colleagues cite research suggesting that menstrual cycle phase may affect performance, other studies fail to find a statistically significant effect of menstrual cycle phase on endurance, jumping, and sprinting, or on muscle contractile properties and VO2max. Though body temperature is slightly elevated during the mid-luteal phase, the consequences for athletic performance haven’t been firmly established. In conclusion, while it’s tempting to draw an arrow from physiological changes that take place during the menstrual cycle to outcomes in sports, the evidence often doesn’t support the link.

Illustration of how follicle-stimulating hormone, estradiol, luteinizing hormone, and progesterone vary throughout the menstrual cycle.
Image credit Chris 73 / Wikimedia Commons, CC BY-SA 3.0. Adapted for this blog post.

There’s more to answering this question than studies of physiology, though. Here’s why. If a researcher asked a random sample of respondents whether they thought that women’s athletic performance tended to improve, stay the same, or go downhill right before and during their periods, most respondents would probably say that women’s athletic performance isn’t at its peak at those times. The idea that menstruation and the days leading up to it are associated with impairments in cognitive, emotional, and physical function is widespread. The (sometimes dangerously) off-her-game premenstrual and menstrual woman, in fact, has achieved the status of cultural trope.

The Telegraph article embraces the claim that premenstrual and menstruating women operate at a deficit as non-controversial, implying in its opening lines that Rose Lavelle scored the game-clinching goal in spite of the fact that her period was due to arrive the next day. The article takes for granted the need to “minimise the adverse performance impact of the menstrual cycle.” When people evaluate their own performance, they bring with them negative ideas about how their cycles might affect them. Studies have shown that these negative perceptions can generate two kinds of self-fulfilling prophecy: they can change peoples’ perceptions of their performance, and they can actually impair performance.

On the question of perception, research suggests that, when it comes to menstruation, there may be a split in how people report their symptoms depending on when the question is asked. If respondents describe how they’re feeling in the moment, they report feeling better than they do if asked later to recall how bad their symptoms were. Thinking back to what their premenstrual and menstrual phases were like, people may unconsciously shape their narratives to meet the expectation that they had negative experiences. Furthermore, in the current framing, certain phases of the cycle are described as sources of performance loss and therefore abnormal. We don’t know what would happen if, instead, other phases were highlighted for giving athletes mid-follicular or peri-ovulatory super powers.

The effect of perception on physiology is powerful. In a research study designed to test the effects of cycle phase beliefs, women who were led to believe that they were in a different cycle phase than their actual phase produced symptom recall reports reflecting cultural expectations to a greater extent than their true cycle phases. That is, when told that they were premenstrual, they reported having premenstrual symptoms although they were not in fact premenstrual.

It’s not impossible, therefore, that focus on menstrual cycle phase when the phase is believed to impair performance turns the causal arrow around and impairs women’s performance. Evidence supporting the claim that menstrual cycle phase affects athletic performance is spotty at best, but it’s pretty clear that negative stereotypes about menstruation infiltrate peoples’ experiences of their bodies--and the function of those very bodies. If illnesses caused by medicine are “iatrogenic,” performance differences associated with menstrual cycle phase might be “sciogenic,” i.e., caused by science trying to show that they exist.1

Is it important?

Readers who encounter unwanted symptoms during the premenstrual or menstrual phases might be furrowing their brows at this point. To be clear: the claim here is not that all negative experiences associated with the menstrual cycle are the result of self-fulfilling prophecy. Anything that a person perceives as impacting well-being and performance needs to be taken seriously, including symptoms that accompany specific phases of the menstrual cycle. Failing to do so can lead to the under-diagnosis of medical conditions like endometriosis, particularly for women of color, whose pain and suffering tend to get taken less seriously than the medical complaints of white women. It’s also just good practice to take people at their word about how they’re feeling.

The concern is that routine focus on menstrual cycle phase could crowd out other important (maybe more important) sources of variation that affect athletic performance and that professional athletes generally take into account. These might include seasonal or environmental allergies; responses to heat, cold, humidity, and altitude; and other, less predictable or cyclical conditions and stimuli. A focus on the menstrual cycle could also divert attention, the way a magician uses misdirection, from other (likely more important) sources of variation that aren’t generally taken into account, including the bodily effects of stress from worry about finding and/or affording childcare, gender inequities in pay, or having to initiate a lawsuit to access equal pay2. Chalking performance up to menstrual cycle phase, that is, could become a shortcut that obscures or discounts other significant sources of performance variation, including major sociopolitical inequities like those mentioned above. The power of science to confer significance on the thing it measures could make the menstrual cycle important as a result of all the attention paid to it, while attention isn’t paid to, say, systemic gender inequality.

Could menstrual cycle science do harm?

Is it possible that a routine focus on menstrual cycle phase as a determinant of athletic performance could do harm? The Telegraph article suggests that there’s only upside: a margin gained, however slim, is still a margin. The menstrual cycle, per its name, offers the benefit of predictability--at least for some people, some of the time. But without clear evidence of negative effects on performance, could all the attention reinforce the pathologization of women’s bodies and minds?  

Historically, a focus on the menstrual cycle by anyone with an interest in controlling women, excluding them, or extracting labor from them hasn’t gone well for people who menstruate. Some physicians thought menstruating women shouldn’t go to school. Women air service pilots in World War II were not supposed to fly during their periods for fear that they might faint. Even today, however, many believe that women are not as rational, self-abnegating, capable, and productive before and during menstruation as they are at other cycle phases. Attempts to mitigate menstrual deficits have been aimed not at addressing situations to which anger, hurt, disaffectation, or apathy might be legitimate responses, but rather at getting women back in line. Winning the World Cup while suing the US soccer federation for gender discrimination hardly constitutes getting in line. However, the implication that the women’s team’s victory had to do with managing the inherently negative effects of the menstrual cycle echoes a deep history of rhetoric aimed at disciplining women by locating vulnerability and weakness in the non-pathological function of their bodies.

Perhaps the US Women’s National Team heroes and their dedicated fitness coaches can teach us how to attend to, celebrate, and push our bodies to achieve great things with the understanding that each body is different every day in ways that, much of the time, have little to do with the menstrual cycle.

1 Thanks to Sari van Anders for “sciogenic” (personal communication).

2 Thanks again to Sari van Anders (personal communication).