Earlier this year the comments of a number of high-profile athletes sparked an important discussion about periods – a complex issue which requires careful management

Dina Asher-Smith grabbed the headlines at the European Championships in Munich as much for her comments off the track as her performances on it. After limping out of the women’s 100m final with calf cramps, she later admitted it was “girls’ stuff” that had caused the issue and called for more research to be done on the menstrual cycle and its impact on performance.

“We see girls that have been consistent have a random dip. Behind the scenes they are really struggling, while everyone is thinking, ‘What’s that? That’s random’. We just need more funding,” she said. “I feel like if it was a men’s issue there would be a million different ways to combat things. But with women there just needs to be more funding in that area.”

In a column for BBC Sport, Eilish McColgan praised Asher-Smith for raising awareness of the issue and detailed how the menstrual cycle impacts her own running. “Some months, it’s manageable. Other months, it’s unbearable,” McColgan wrote. “There’s no telling which Eilish you’re going to get on the day. To try and run, or at least perform to the best of my ability, is an almost impossible task.”

Cue a social media storm in which a wave of female athletes of all levels and abilities agreed that little is being done to help them understand and overcome the inconsistencies in performance presented by the menstrual cycle. 

But this period drama has an enduring and complex plot. Kirsty Elliot-Sale, a professor of female endocrinology and exercise physiology at Manchester Metropolitan University, has been researching the effects of athletes’ menstrual cycles for two decades and agrees that the subject is “under-studied” but argues that there is research being carried out. 

“Academically, it is an area that is much more nuanced than is currently being portrayed on social media,” Elliot-Sale says. “It is true that because of the complicated interplay of endocrinology, physiology and hormonal health, there is a mixed bag of scientific evidence with not all of it using the best methodology, but there is some strong science – and we are constantly striving to produce more of it.”

While athletes are calling for research to be done, researchers are calling for athletes to step forward and take part in studies. “We’ve got research studies running all the time, but there is a real reluctance among top level athletes to take part,” adds Elliot-Sale. “Elite women tell us there are too many studies using general exercisers and not enough research on people at their level in sport, but the only way to push forward is to work together.” 

No two athletes are the same

What the existing scientific evidence does tell us is that no two women respond in the same way to different phases of their menstrual cycle. “When we look at that body of research we find there is just so much variability, not just between women, but within one woman’s cycle,” says Elliot-Sale. “While some women do experience these negative side-effects or symptoms, just as many don’t.”

There exists confusion, she says, not just among male coaches, but among female athletes themselves about what the menstrual cycle is and how it might, or might not, affect training and performance.

In most women, the key reproductive hormones oestrogen and progesterone rise and fall in a fairly predictable pattern over an approximately monthly cycle, although regular cycles typically range from 21 to 35 days.

“In the early follicular phase both of these hormones are at their lowest levels,” says Elliot-Sale. “Oestrogen then rises rapidly around the time of ovulation, menstruation occurs midway through the cycle and second half of the cycle, the luteal phase, is when both hormones are raised.” 

For those who do experience a drop in performance it is around the time of their period. But Elliot-Sale says that women athletes who take the contraceptive Pill often complain of period pain and performance dips when it simply can’t happen.

“Women on the Pill have a withdrawal bleed but they do not have a period,” she says. “Any cyclic dips they experience in training might well exist but they have nothing at all to do with the menstrual cycle because they don’t have one.” It is, says Elliot-Sale, “physically impossible to have period pain on the Pill” and yet when elite female athletes are given questionnaires they usually believe the two are related.

In women who do menstruate, quite how differently they respond to the hormonal cycle was demonstrated in a 2020 meta-analysis Elliot-Sale and colleagues from different UK institutions including Northumbria University, Nottingham Trent University and Robert Gordon University in Aberdeen, conducted. 

They reviewed 78 studies involving a total of 1193 women that looked at the impact of the menstrual cycle on performance. Measurements of all aspects of performance – including strength, endurance, times, VO2 max and power output – were taken at different phases of the monthly cycle and the findings, published in the journal Sports Medicine, did show a pattern of performance decline in the follicular phase of the cycle.

Unexpectedly they found that the drops were not significant. Indeed, performances deteriorated only by “a trivial amount” when compared with other phases and their conclusion was that there is not enough evidence to issue general guidance for athletes on training or competing with their period. 

A caveat with that paper was that many of the studies included were of poor quality and design. But, even when these were removed from the analysis, Elliot-Sale says the outcome remained that the overall effect on performance is negligible.

Last year, French scientists looked more specifically at the effects of a woman’s cycle on elite athletic performance, trying to determine whether even small or “trivial” differences impacted results. Of 218 relevant studies they found only seven that precisely measured a menstrual cycle phase on physical or performance parameters, most using hormonal screening through blood, saliva or urine tests. 

Two of the studies relied on athletes’ training diaries. Results, published in Frontiers In Physiology, found that some women experienced ligament stiffness, lower levels of power or endurance or psychological issues such as a drop in perceived competitiveness or decision making skills. But others did not, and the researches said the outcomes were too variable to be considered conclusive.

Keeping track

Elliot-Sale says there needs to be some “ownership” of tracking cycles by women, their coaches and any support team members. She found it surprising that so many elite athletes seemed to suffer unexpected side effects of their menstrual cycle almost simultaneously this summer.

“Your ovaries don’t just kick in for the first time at a major championship,” she says. “Surely athletes would have been having periods for 10-20 years by the time they are at that level and would not leave it until the month before one of the most important events of their lives to work out that their period might fall on the day of a heat or final?”

Elliot-Sale advises ongoing personal tracking of symptoms and timings, keeping a detailed diary of evidence and careful planning ahead. “It might be that a massage at a certain time of the cycle is helpful or that tweaking your nutrition at different times can help,” she says. “But if you have a major summer competition, these are things that need to be in place as early as January.”

Best avoided, though, are trendy apps that claim to help women plan their training in accordance with the ebb and flow of their cycle. Many elite sporting organisations have even banned these apps because their athletes are adversely affected by the advice given.

“These sorts of menstrual tracking apps are not based on any scientific evidence and don’t track anything you don’t tell them,” says Elliot-Sale. “They base their advice purely on the dates of your period and no hormones or blood levels are involved so it means nothing.” 

Looking at the positives of periods

There’s concern, too, that high-profile sportswomen commenting publicly about painful periods and problematic menstrual cycles will send a negative message to younger athletes. Pippa Woolven, former international athlete and founder of Project RED-S, says: “We need to be very careful about positioning periods in a negative light,” especially when such progress is being made about the protective effects of the menstrual cycle on skeletal and physiological health.”

Elliot-Sale agrees that it is “a potentially dangerous message to suggest periods are something we need to try to avoid in sport” and that they are actually a marker of excellent health.

“It used to be a badge of honour that you were training hard enough, meaning you were elite, when you lost your period,” says Elliot-Sale. “But we now know that there are so many physiological and performance consequences associated with that and essentially your body has had to make a sacrifice to fuel your sport and not your reproductive axis because there is not enough fuel to do it all.”

As a coach myself, following the social media debate earlier this summer I was approached by two 15-year-old runners who became visibly upset about competing with their periods and fearful that they would cause pain that would mean they wouldn’t race well. 

Shireen Higgins, who coaches some of the UK’s top junior female middle-distance athletes at Windsor, Slough, Eton and Hounslow AC, says that while periods might be considered inconvenient for all women, athletes included, they are a natural and necessary part of physical development. 

“They are essential if you want to have a healthy and long-term athletics career as well as strong bones in later life,” Higgins says. “The message should be that the cycle needs to be managed and not avoided.”

Once girls reach puberty, Higgins suggests blood tests and taking extra iron and seeing a doctor if they get heavy bleeding, pain or excessive mood swings. “If symptoms are severe, then it is important to work with your doctor, ideally someone who understands sport, to discuss possible next stages,” she says. “For older athletes an option might be the Pill to control your cycle and you will need to work with your doctor to choose a pill carefully in and may need to try different types to find one that suits.”

She believes it is risky “to tell young girls that they will run worse at certain points of the cycle”.

Elliot-Sale welcomes the increase in conversations about the menstrual cycle and sport. “Publicly it has gone under the radar for so long and it’s a good thing we are now talking about it,” she says. “Yes, there are genuine cases where races are lost because of the menstrual cycle, but the danger is it becomes too easy to blame periods for poor performance and that will weaken women’s sport. Periods are healthy and there is always something that can be done to make them less problematic.”