Got Gains? What We Know About Working Out On Birth Control

You’re weightlifting at the gym and heading out on runs twice a week — you’re putting in the effort, so you definitely want to see some payoff. While there’s more than one factor that affects how your body responds to exercise, it’s natural to wonder whether your hormones might be affecting your fitness. Could your birth control be affecting the impact of your workouts?

The sex hormones in birth control do affect on how our muscles and cardiovascular systems work,¹ so it’s likely that they impact how our bodies respond to exercise. But, like a lot of things with hormonal birth control, the effects aren’t always straightforward, and the studies that do exist sometimes say different things.

Current scientific consensus is that hormonal birth control likely has a small, but negative effect on muscle growth and recovery after a workout.² But what that impact looks like can depend on the type of birth control you’re on, as well as how that interacts with your own unique biology. Confusing things further, different formulations of birth control contain different types of progestins — like norethindrone, levonogesterel, or drospirenone — which can affect the body differently. That means there’s no one-size-fits-all answer.

Your choice of birth control likely won’t make a huge difference to your physical fitness.

But unless you’re an athlete who’s super focused on pushing the envelope, your choice of birth control likely won’t make a huge difference to your physical fitness. Let’s walk through what we do, and don’t, know about working out on birth control.

How the Hormones in Birth Control Affect Your Body

All forms of hormonal birth control contain a synthetic version of the sex hormone progesterone called progestin.³ Some contain estrogen as well.⁴ These hormones work to stop ovulation, or the release of an egg from your ovaries, and also make it harder for sperm to swim.⁵

But progestin and estrogen play a lot of other roles in our bodies, too. The sex hormones influence mood, bone formation, neurological health, acne, cardiovascular health, and more.^5-6 That’s why hormonal contraceptives can come with side effects — both good and bad ones.

Most importantly when it comes to exercise, progestin and estrogen impact how both muscles and the cardiovascular system function. Estrogen increases blood flow to the heart and muscles,¹ and can increase cardiac output. It also likely plays a role in helping to maintain muscles. Some studies also show progesterone could increase the synthesis of muscle protein.⁸

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Working Out On Birth Control

A number of studies have looked into how various kinds of hormonal birth control affect exercise performance. But results are mixed, which makes drawing conclusions challenging, especially when different studies look at different formulations of birth control. One consistent finding is that the sex hormones in birth control affect various kinds of exercise differently, like lifting weights versus going for a run. And birth control does also seem to change how your body recovers after exercise, which is a big factor in how your body adapts to training.

Birth Control and Muscle Growth

In one small study, scientists had 28 people — half on birth control, half not on birth control — do leg exercises for ten weeks to see if there was a link between birth control and muscle growth. Those using birth control gained more muscle mass than those not on birth control.⁹ But another study with a similar setup saw the opposite effect after ten weeks of exercise: those using birth control saw smaller gains in muscle mass after the workout program.¹⁰ Researchers noted that the type of progestin also seemed to play a role in muscle building: the more androgenic, or “male-like” progestins, like levonorgestrel and norithendrone,¹¹ were linked to even smaller gains in muscle mass compared to progestins like desogestrel and norgestimate.

The type of progestin also seemed to play a role in muscle building.

There’s an additional caveat to both of those studies: While they found that birth control affected gains in muscle mass after working out, both studies reported that there were no changes in muscle strength between study groups. In other words, the people on birth control ended up just as strong as the people not taking birth control.

Birth Control and Endurance

Some studies show that cardiorespiratory performance (i.e., how the heart and lungs deliver oxygen to your muscles during physical activity) might be slightly impaired by birth control,¹² and that maximum oxygen consumption (VO2 max), which shows how hard your body is working while exercising, might also be a bit worse.¹³

Another study that analyzed resting heart rate and heart rate variability in ~4,600 people as measured by a fitness tracker found that people taking birth control with estrogen also might not recover quite as well after a workout, though again, the effect was small.¹⁴ People on progestin-only contraceptives recovered about as well as those not taking hormonal contraceptives.

Where does all of this leave us?

The most comprehensive review study of hormonal birth control and exercise to date says contraception “might result in slightly inferior exercise performance on average when compared to naturally menstruating women” (emphasis added). So, there may be a small negative effect, but only maybe sometimes.²

But the review also notes that most of the studies the researchers looked at were low quality and quite small (studies included just 10 people on average). There was also a lot of variation between studies when it came to the effects of birth control on exercise performance, and the review lumped together studies on both muscular strength and endurance.²

Overall, the author’s conclusion was that birth control might have a slightly negative impact on exercise performance. But the effect was so small that it was really only an issue for competitive or professional athletes who have reason to track and monitor even the tiniest gains in fitness. Additionally, there was so much variability in people’s responses to exercise on birth control that it was hard to make generalized recommendations.²

What Do I Need to Know About Birth Control and Exercise?

Based on the best evidence we have, birth control may have a small, but negative effect on physical performance. But those findings come with considerable caveats, and are from small, lower quality studies. Moreover, some of these studies contradict each other, and scientists say we need more research. The medical research gender gap that favors men over women in research is definitely to blame here, and while that’s beginning to change, it might be some time before we see truly equitable studies.

Being on birth control has some other benefits for athletes and physically active people.

If you’re just trying to get more fit or train for your local 10K, there’s no evidence right now that your birth control is going to make or break your goals. But you should also remember that being on birth control has some other benefits for athletes and physically active people. For example, skipping your period can be one less thing to worry about when you need to perform at your best.

Ultimately, the same advice applies to making decisions about birth control as it does to working out: You should listen to your body and figure out what works for you. Different people respond to the same kind of birth control in different ways. If you feel like your birth control is dragging you down, there are many more options to choose from.

Want to read more about finding the right birth control for your body? Get started with The Birth Control Test.