While more athletes and coaches are talking openly about the potential influence of hormones and birth control on training and performance, the science hasn’t quite caught up. (Photo: Miquel Llonch/Stocksy)

Is Your Hormonal Birth Control Affecting Your Athletic Performance?

Athletes of all levels have considered whether their choice of birth control might influence how they train, recover, and perform. But the answer is complicated. Here’s what you need to know.

Miquel Llonch/Stocksy

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At the awards ceremony at the 2018 Wildflower Triathlon, professional triathlete Kelly O’Mara wondered if she should quit her birth control pill. She was sitting with several other athletes and they couldn’t believe she was still on birth control. They claimed the pill was bad for performance. Didn’t she want to be fast?

It wasn’t the first time O’Mara had heard this advice. This time around, it seemed like everyone was off birth control. She’d previously looked for research into the link between hormonal contraceptives and athletic performance and had come up empty-handed, but the anecdotal evidence was convincing. Aside from the pros around her, her coach knew people who improved when they ditched birth control, including some of her own athletes. One of O’Mara’s friends, an athlete of a similar level, placed second at an Ironman after going off hormonal contraceptives.

O’Mara describes herself as a solid middle-of-the-pack athlete. She says she felt like she was missing “some obvious breakthrough” and dropping the pill seemed like the solution that was going to help her finish at the top. She thought, “This is what’s holding me back. This is why I’m not on the podium.”

Among athletes and the performance-driven set, the desire to be the best can often lead to a never-ending quest to find the elixir, superfood, or training method that will ultimately unleash one’s performance potential. “Every athlete has had days where you’re batting above your weight and everything feels easy,” O’Mara says. “And there are days where you can’t hit anything. Of course, you want to know why that is.”

For female athletes, the menstrual cycle is the latest darling of the sports-science world. In recent years, medical practitioners have acknowledged that the period is more than an indicator of fertility. Rather, it’s akin to a vital sign, like blood pressure and pulse rate, and can offer a check on your health and hormones. This has given rise to the practice of cycle syncing—tailoring your training to the phase of your menstrual cycle in order to take advantage of the body’s hormonal peaks and valleys.

In light of this shift, many people, particularly on social media, are positioning the menstrual cycle as a crystal ball that holds the secret to optimal health and athletic performance. Do this when you’re in a low-hormone phase. Don’t do this when you’re in a high-hormone phase. Scrolling through your feed, it can be easy to conclude that if you can’t track your natural cycle, you’re at a disadvantage. It’s led many, like O’Mara, to consider skipping hormonal contraceptives.

While more athletes and coaches are talking openly about the potential influence of hormones and birth control on training and performance, the science hasn’t quite caught up. Clare Minahan, an associate professor of exercise and sport at Griffith University in Australia, says it’s a leap to conclude that athletes should swear off hormonal contraceptives entirely. “I could cherry-pick papers from scientific journals to say you should get off hormonal contraception or you should get on hormonal contraception, but that’s not consensus,” she says.

Many people, particularly on social media, are positioning the menstrual cycle as a crystal ball that holds the secret to optimal health and athletic performance.

Dr. Kate Ackerman, the director of the Female Athlete Program at Boston Children’s Hospital, agrees. “Many people can safely be on hormonal contraceptives for years,” she says. “Especially with the changes in legislation in the U.S. around abortion, even more patients are coming in and asking about safe ways to keep from getting pregnant while being healthy and performing well.”

Roughly half of athletes who menstruate use some form of hormonal contraceptive. Oral birth control pills, arm implants, patches, vaginal rings, injections, and some IUDs introduce synthetic versions of female sex hormones into the body. These can be manufactured forms of estrogen, progesterone (the synthetic version is called progestin), or a combination of both. The exact dosage and potency depends on the type and brand of contraceptive.

Generally, these man-made hormones override the menstrual cycle and suppress ovulation, preventing pregnancy. That means that the body may not experience the same hormonal ups and downs as it would naturally.

Some types of hormonal birth control are designed to mimic the menstrual cycle. For example, the oral contraceptive pill generally includes 21 days of “active” pills followed by a series of placebo pills that don’t have hormones. Most people will experience some bleeding during the contraceptive’s placebo phase.

One common misconception is that the bleeding that occurs during this stage is equivalent to a period. Doctors and researchers call it “withdrawal bleed.” Hormones in the contraceptive build up and maintain the uterine lining—without these hormones in your system during the placebo phase, the body sloughs off the lining, resulting in bleeding. That means a withdrawal bleed isn’t a good indicator of hormonal health, and it can mask signs of underfueling and menstrual dysfunction.

Of course, many people choose to take hormonal birth control for reasons other than contraception. “Doctors may prescribe different types of progesterone and dosing of pills to address different concerns,” Ackerman says. “Some might be on the pill because they have Polycystic Ovarian Syndrome (PCOS) or they want to treat their acne.” Birth control might also help manage heavy menstrual bleeding, bloating, and other cycle-related symptoms.

The side effects of hormonal contraceptives can be debilitating for some athletes, influencing their mood, desire and ability to train, and athletic performance. Former collegiate runner Hannah Wohlenberg began taking the pill between her junior and senior years of high school because she started Accutane treatment for her acne. (Because Accutane may cause serious birth defects, those who choose to take it and could become pregnant are required to commit to using two forms of birth control as part of the Food and Drug Administration’s iPLEDGE program.) Almost immediately, she experienced asthma-like symptoms.

The timing wasn’t great. During Wohlenberg’s junior year, her team finished second at the California state cross-country championships and she finished seventeenth individually. Heading into senior year, she wanted to build on her success, especially with college on the horizon. Instead, her training tanked. “My body wasn’t responding. It felt very different and heavier,” she says. She couldn’t finish workouts and had to stop because she couldn’t breathe. She quit the pill and Accutane after a few months and “everything cleared up.” She had a great track season and went on to run for Loyola Marymount University.

Wohlenberg never got an explanation for what happened to her body. While there’s mixed evidence on the connection between the pill and symptoms like asthma, she was wary of hormonal contraceptives because of her personal experience. She wishes her doctor had prepared her for how the medication and its side effects might affect her performance. When she investigated birth control options again in college, she relied on the advice and experience of friends and teammates and opted for a copper intrauterine device (IUD), which doesn’t contain hormones.

Like Wohlenberg, professional track and field athlete Colleen Quigley opted for a copper IUD. She was concerned that hormonal birth control would disrupt her body’s pattern of hormonal fluctuations and influence her mood and athletic performance, something she experienced while on the pill in high school.

Quigley wanted contraception that would prevent pregnancy but allow her to get her natural period too. “I use my monthly period as a signal that I’m doing a good job balancing my training and my fueling,” she said in an email. It gives her the feedback she needs to stay healthy.

Quigley shared her experience on social media last year and the discussion was lively. In the comment section and Quigley’s DMs, people shared their own experiences with IUDs—some positive, some negative—and asked questions.

Experiences like Wohlenberg’s can be common, since doctors don’t often have a lot of information to go on. Overall, there isn’t much data on the side effects associated with hormonal contraceptives. There’s even less research on the connection between hormonal contraceptives, athletic training, and performance.

Of the sports science studies that do exist, the quality varies greatly. Many studies are small, involving only a handful of participants. Some combine participants on different types of contraceptives or include only those taking oral contraceptive pills. Others studied women on older formulations of birth control. Plus, researchers don’t always note the type and dose of hormones.

Taken together, it’s hard to draw conclusions across studies. A 2020 systematic review and meta-analysis compared exercise performance of those on oral contraceptive pills against a control group of naturally menstruating people. They found that while pill users experienced slightly decreased performance, the effect was “trivial” at best.

For instance, research suggests that hormonal birth control decreases aerobic capacity: studies from the early 2000s found that VO2 max may be reduced by roughly five percent compared to those who are not on oral contraceptives. However, it’s unclear whether the findings still hold true. These studies haven’t been replicated, and birth control formulations have changed in the years since.

Still, some useful nuggets are beginning to emerge from the scientific literature. Compared to naturally cycling individuals, Minahan says, “there’s quite conclusive evidence that women who take hormonal contraceptives are more likely to show evidence of delayed onset muscle soreness and muscle damage” after performing exercise that’s new to them or that focuses on the muscle lengthening phase, like lowering into a squat or downhill running. Studies have also found higher markers of inflammation, like C-reactive protein, in elite and recreational athletes taking oral contraceptive pills, which could affect training adaptation and recovery. According to Minahan, there’s some evidence that hormonal contraception may reduce the chance of teenage athletes reaching peak bone mass, and they may also be at risk for decreased adaptation to resistance training.

With the increased interest in this area of study, researchers are paying more attention to how the formulation of different contraceptives may affect how athletes adapt to training. Still, more high-quality research is needed to reach a consensus and better guidance for athletes and medical providers.

When discussing birth control options with patients, Ackerman says she considers the whole person: their concerns, priorities, and lived experience. While there may be some potential benefits to a natural cycle, those benefits may be negated if her patient experiences horrible cramping, heavy bleeding, or mood swings with her period. Plus, her patient may train more consistently while on the pill because she’s not worried about getting pregnant or experiencing heavy periods. “Ultimately, your performance will be better because you’re able to get more training days in,” she says.

For O’Mara’s part, her periods were “terrible” before starting the pill during college in the mid-aughts. She’d be in so much pain that she’d vomit. The pill lessened her symptoms. When she quit the pill—she tried twice over the span of a few years—her performance didn’t improve.

While there may be some potential benefits to a natural cycle, those benefits may be negated if a patient experiences horrible cramping, heavy bleeding, or mood swings with her period.

The biggest concern among medical practitioners is that hormonal contraceptives may mask the loss of menstruation and the symptoms of relative energy deficiency in sport (RED-S), a condition that develops when the body doesn’t have enough fuel to meet the demands of training and daily life. RED-S can lead to disrupted and absent menstrual cycles and can affect bone health, immunity, metabolism, cardiovascular health, and mental health, not to mention athletic performance. If an athlete is on birth control that suppresses her menstrual cycle or causes a withdrawal bleed, it’s hard to know if the underlying cycle is functioning normally.

“Those are the people I want to be careful with,” says Ackerman. “If I have a patient with RED-S and she doesn’t get her cycle, I don’t want to put her on the pill. I want to figure out why she doesn’t get her period.”

Once an athlete’s nutrition and body composition are normalized and can sustain a regular menstrual cycle, Ackerman says she might be a candidate for hormonal birth control. However, if there’s a risk that her weight or body composition might fluctuate in a way that would put her at risk for RED-S or losing her cycle again, whether due to the demands of training or because of an underlying eating disorder, Ackerman might suggest something like the copper IUD instead.

For an athlete not at risk of RED-S who wants to stop the pill for performance reasons, Dr. Emily Kraus, clinical assistant professor of orthopedic surgery and program director of the Female Athlete Science and Translational Research program at Stanford University says, “We don’t have enough evidence to say, ‘Get off the pill.’” Instead, she would try to understand the reasons the athlete started taking hormonal birth control and how long they’ve been on it.

Kraus says athletes can feel empowered while on hormonal contraceptives, but it starts with understanding their own body and the formulation of birth control they’re taking. While there’s the perception among most women that hormone levels are flat while on contraceptives, there can be hormonal fluctuations, which can influence how the body feels and responds to training. Experts recommend tracking symptoms—both positive and negative—and any withdrawal bleeding while on hormonal contraceptives. Based on this information, you can adjust nutrition, training, or recovery strategies. Your physician may also adjust your birth control or suggest a different type to minimize side effects. “Newer generations of contraceptives can have fewer side effects,” she says.

Deciding whether to take  hormonal birth control isn’t black and white. The effects of naturally occurring and synthetic hormones on the body can vary greatly from person to person, and when it comes to fitness and athletic performance, it’s only one part of the bigger picture. Consult a medical doctor, such as an OB/GYN or endocrinologist, and share both your reproductive and athletic goals with your provider.

But one thing is clear: “This is something we absolutely need to talk about more,” Quigley says.

Lead Photo: Miquel Llonch/Stocksy