You’re an Olympian. You have your period. Now what?

On a good day, your period is a mild annoyance. On a bad day, however, it can feel like a thousand tiny elves repeatedly kicking you in the abdomen. So imagine, if you will, that you’re on the world’s largest athletic stage—competing for personal achievement, glory for your country, and a coveted medal—when Aunt Flow decides she wants to be a part of the action.

More than 10,000 athletes from around the globe are expected to descend upon Rio de Janeiro, Brazil, this week for the summer Olympic games, and about half of those athletes will be women. While men have biological imperatives of their own, women have a literal cycle that, for most, results in at least a few days of vaginal blood-letting each month. But does menstruation have a real impact on athletic performance?

The short answer is that there is no short answer to how periods impact female athletes. Despite a wealth of clinical studies on how all manner of bodily ailments affect athletes, there’s (maybe not shockingly) a dearth of hard facts on how intense physical training affects a woman’s cycle, and vice versa.

Georgie Bruinvels is a PhD student at St. Mary’s University, Twickenham, in London, and she is focusing on her research on this very topic. (Specifically, how the menstrual cycle affects iron levels in female athletes.) But before she could dive into her research, Bruinvels had to check out all the existing data, and she was disappointed to find that she came up short—too short.

In a June editorial published in the British Journal of Sports Medicine, Bruinvels and her colleagues pointed out just how lacking the current body of research is on periods and athletic performance. After reviewing 1,382 sport and exercise studies that involved more than 6 million participants, the authors found that women were much less likely to be included than men. Why? “The complexities of the menstrual cycle are considered major barriers to the inclusion of women in clinical trials.”

The authors also reported that 41.7% of exercising women believe their period has a negative impact on training and performance—but due to “the dearth of sports and exercise research in women, explanations for this are lacking.” While heavy bleeding with an undiagnosed iron deficiency could explain what these women experience, they added, no one really knows.

“This area really is lacking, which was why we wrote the editorial,” Bruinvels told me in an email. “We wanted to highlight this [void] and encourage people to start researching in this field. Which hopefully it will. I appreciate it is a long process but we have to start somewhere!”

SAN JOSE, CA - JULY 10:  Gabrielle Douglas competes on the balance beam during Day 2 of the 2016 U.S. Women's Gymnastics Olympic Trials at SAP Center on July 10, 2016 in San Jose, California.  (Photo by Ezra Shaw/Getty Images)Getty Images

No athlete wants to have her period while pulling off moves like this one.

Despite the lack of research, female professional athletes can take certain measures to decrease the likelihood that menstruating will interfere with medaling. Dr. Petra Casey is an associate professor of obstetrics and gynecology at the Mayo Clinic, and in a recent phone conversation, she offered a bold solution for avoiding your period at game time: ditch it altogether.

“The mindset of ‘I must have a period every month’ is really changing quite a bit, and women are much more accepting of irregular menstrual periods, or no periods, and some people actually want no periods because of the convenience,” she told me. “It’s very advantageous if you don’t need pads when you’re running or swimming. There are no health issues with that. In fact, it’s quite healthy to not have a period for a long period of time.”

The popularity of IUDs and hormonal birth controls that cause fewer or no periods has lead to this change in attitude. And Casey says that fewer periods can reduce the risk of anemia or endometriosis, since the body experiences less monthly blood loss.

Casey also pointed out that some female athletes lose their periods anyway as a result of their fierce athleticism—particularly endurance athletes, like runners or triathletes, who are exceptionally lean and have a Body Mass Index (BMI) that won’t support a period. This is called “hypothalamic amenorrhea,” which Casey said is a “protective mechanism” by the body when it knows it doesn’t carry enough body fat to sustain a pregnancy.

Luckily, even if an athlete loses her period for a time, Casey said she shouldn’t worry about any longterm effects on her reproductive health. Once a woman scales back her activity and gains weight, her period typically comes back as normal. Even for very young athletes, like gymnasts, they may just start their period a bit later in adolescence without concern. “It’s a very reversible process,” Casey said.

That said, doctors will often take special precautions to make sure adult athletes who stop menstruating stay healthy. “One of the things we worry about in female athletes when they don’t have periods is, do they have enough estrogen to sustain bone maintenance and prevention of osteoporosis?” Casey said. That’s why doctors will put these women on a hormonal birth control to replenish estrogen.

When I asked Casey whether professional athletes who regularly menstruate might struggle with their cycle’s effects on performance, she echoed Bruinvel, saying, “I don’t know if we have enough data to say with certainty.”

Some athletes and coaches do pay special attention to the menstrual cycle and what it can do to hurt or help performance, despite hard evidence. Hannah Macleod, a member of Great Britain’s Olympic field hockey team, told the Telegraph in January of last year, “We actually had our menstrual cycles tracked by our coach for a year prior to the [last] Olympics. It was to get an idea of what stage we’d be at, during our cycles for the games.”

Macleod said menstruation is “something we have never been shy talking about.” From her perspective, “There’s a vast difference from athlete-to-athlete in terms of what they suffer. Some players get a bit moody and lose coordination. Exercises can feel a little bit harder, and it can change your body temperature.” She said the players continue to provide the coach with updates, but despite the free flow of conversation, her teammates still feel embarrassed by their periods.

The Olympian’s comments came in the days following a loss at Wimbledon by British tennis player Heather Watson. Watson blamed the defeat on extreme period symptoms, including dizziness, nausea, and low energy levels, but noted that these symptoms are still not taken seriously by the athletic community.

Former British tennis champion Annabel Croft came to Watson’s defense, calling menstruation “taboo” in tennis, and commenting that “Women’s monthly issues seem to be one of those subjects that gets swept under the carpet and is a big secret…I think women do suffer in silence.”

Thanks to modern developments in birth control, though, perhaps female athletes are figuring out individualized ways to suffer less and focus more on the task at hand: going for gold. If nothing else, self-medicating may be the best band-aid we can hope for until exercise scientists start to include more women in their research. For now, if the big day comes for a female Olympian’s 500-meter swim, uneven bars routine, or basketball game and menstrual blood is an extra accessory, her only choice may be to stick in a tampon and pray she sticks a mess-free landing.

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