Last year, I came off the pill. After six years of using the medication as an acne treatment and contraceptive, I wanted to start tracking my menstrual cycle more holistically. My mood improved almost overnight, but what I wasn’t prepared for was the change to my running. Soon after taking that last tablet, I started to feel infinitely stronger and fitter, despite my training staying the same. Seemingly overnight, I’d become a better athlete. Was that improvement purely psychological or was the sudden Strava boost linked to a change in my hormonal status?

Science suggests that my experience of post-pill fitness might not be a fluke. A very tiny study, published in the Journal Of Applied Physiology, found that when women started taking the pill, their aerobic fitness decreased by 11% and their peak power on a cycling test went down by 8%.

Another study measured aerobic capacity in 14 highly trained female athletes across their menstrual cycle before assigning them either a hormonal contraceptive pill or a placebo and found that the contraceptive pill group experienced a 4.7% decline in their aerobic capacity, while the placebo group’s slightly increased. Of course, with such small control groups, it’s hard to really come to a solid conclusion, but the findings are nonetheless interesting. 

My pill-free experiment didn’t last long; I was back on oral contraception just three months later. My periods had become semi-regular but were so heavy; going back on the pill meant having some modicum of control over when and how I bled. While it was the right choice for me, I couldn’t stop thinking about the impact the pill might be having on my fitness. So, I rooted around to find a bigger study to see if that might provide more conclusive proof as to its effects on cardio capacity.

A 2020 meta-analysis involving the data of 590 participants found that oral contraception had ‘trivial’ negative effects on exercise performance when pill users were compared to naturally menstruating women. However, we shouldn’t pay too much attention to the findings, says Kirsty Elliott-Sale, a professor of female endocrinology and exercise physiology and the paper’s lead researcher. “‘Trivial’ means smaller than small,” she explains. “Of course, at the elite level, that tiny percent could be really impactful because there are marginal differences between first and third place or getting on the podium or not. But [in these papers], there isn’t enough evidence [to make a concrete conclusion] and much of the evidence is poor quality.”

Based on the little (and variable) evidence available, she says that “there’s no real difference between pill-taking and pill-free days, and really no differences between pill users versus athletes who have a menstrual cycle”. Instead, she believes that an individualised approach – particularly considering the range of pills and hormonal contraceptives now available – is key. She recommends asking yourself the following questions: “As an athlete, do you notice if your performance is affected by taking the pill or being pill-free? Or, if you’re a menstrual cycle athlete, do you notice that your performance changes across different phases of the cycle?”

Keen swimmer Alice Reeves-Turner, 27, has been spending the past few years assessing her own cycle and relationship to the pill. A competitive swimmer until the age of 16, she still regularly races and uses the pill to control her bleeding. “If I don’t want to have a period on race day, I’ll double up my pill packets,” she says. “I’ve found that I’m way more prone to muscle cramps when I’m on my period, especially in my right calf. The moment my period comes to an end, the cramp goes away.” Being able to avoid that very real physical reality, she believes, makes the potentially tiny reduction in power worth it. 

Most pills involve having a break week, during which time you’ll bleed. That’s not the same as a menstrual period – something Professor Elliott-Sale says people don’t always totally understand. “The first thing the pill does is stop the production of oestrogen and progesterone by the ovaries, so there’s no menstrual cycle. You end up down-regulating both of those hormones to flat lines,” she explains.

She says that within an hour of popping a pill, the hormones in your bloodstream peak before going on to drop throughout the day. On the 21 days you take the contraceptive, you’ll have that hike in hormones, and on the pill-free days, you won’t – but your natural hormonal production will still be flatlined. That’s why the review mentioned above examined pill-taking and pill-free days rather than long-term pill use. As Professor Elliott-Sale explains: “If oestrogen and progesterone affect any aspect of performance, you might see a difference in performance on the days when you’re taking the pill versus the days when you’re not.” In other words, you don’t need to completely come off contraception to assess whether your fitness levels change. 

Dr Bella Smith, an NHS GP, women’s health specialist and co-founder of The Well HQ, strongly recommends tracking your cycle and symptoms before making any big contraceptive decisions. While pill users won’t have a proper ‘cycle’, tracking things like mood, performance and bleeding means you’ll have your own data to explore if/when you do decide to come off oral contraception.

“Someone can come off the pill at any time – the main thing, however, is not to put yourself at risk of unwanted pregnancy,” says Dr Smith. “I suggest that you keep a symptom diary, tracking how you feel over a three-month period. Then, you can work out what is normal for you and what is medically-induced by the pill.”

Dr Smith, who co-authored The Female Body Bible, highlights how important it is to recognise that withdrawal bleeds aren’t menstrual periods, especially for very active women who might be at risk of RED-S. “We know that having a regular bleed is a sign that you are fuelling correctly. If you are on the pill, you cannot rely on that bleed because it’s not a real period.” Beyond tracking blood, she advises closely monitoring energy levels, gastrointestinal symptoms, mental health and injuries.

Dr Smith says that while most combined pills use the same type of synthetic oestrogen, the combined and progestogen-only pills can contain one of four ‘generations’ of progestin. Those generations are based on their chemical makeup and date of release, and each comes with its unique set of pros and cons, she explains. “They have different risk and side effect profiles to each other, and some are used to treat specific conditions. For example, the first and second generations are more ‘androgenic’ [with similar effects to testosterone] than the third and fourth, and that comes with risks and benefits.” She adds that GPs will take various factors like age, breast cancer or blood clot risk into account when prescribing these medications, as well as assessing the purpose of the prescription (ie whether you’re going on the pill for contraception, acne or hormone-sensitive conditions like endometriosis or PCOS).

While there isn’t enough evidence to warrant official guidelines on oral contraception and exercise, we do know that certain hormonal profiles can have an impact on the way our bodies operate. Androgens, for example, influence muscle growth and repair, so using an anti-androgenic pill (eg for acne or body hair) could possibly affect your muscle-building ability and power. 

“The main focus for research tends to be on the menstrual cycle, but not enough attention is paid to hormonal contraceptive users,” says Professor Elliott-Sale. “That’s not to say there aren’t people out there researching this particular topic, but I do think that in women’s health and women’s sport, it is still a little bit overlooked and overshadowed by periods.”

She would like to see more contraceptive diversity in future research. “How can we speak to all athletes? We should be able to produce data on everyone, from pill users to women who’ve had the injection or hormonal coil.”

Interestingly, when it comes to everyday active women, Dr Smith says my own experience of quitting the pill and going back on it weeks later is a trend she’s seeing in clinic. “I’m finding that a lot of women stop taking the pill, work out what is normal for them, realise that there are still benefits to being on hormonal contraception and go back to it – but this time more informed about what it’s doing.”

While Professor Elliott-Sale understands that people want answers, the reality is that we don’t yet have enough high-quality evidence to make any solid conclusions about fitness and the pill… yet. She concludes: “Whether you’re an oral contraceptive user or a menstrual cycle athlete, we want credible science to support this. We want it to be evidence-based. And that takes a little bit of time.”

Images: Getty