Maybe you’re a marathoner who’s been trying to boost their VO2 max to no avail. Or, perhaps you’re a weight lifter struggling to build muscle. Possibly, you’re a CrossFit enthusiast who’s been stuck at the same total score despite doing everything you can to see gains. Regardless, if you’re toiling away at training and still not seeing results, there could be a surprising culprit undermining your efforts: your hormonal birth control pill.
That’s right, the estimated 14 percent of people on the pill between the ages of 15 and 49 have reason to question whether their oral contraceptive is blocking their fitness goals because, while research is limited, recent data suggests that it could impair muscle growth and hinder cardiovascular capacity (more on that below).
Ahead, three hormone and women’s health experts explain exactly how the hormonal birth control pill can potentially impact athletic performance.
3 ways birth control pills affect athletic performance
1. May mask symptoms of overtraining
For athletes and people who work out a lot, changes to your menstrual cycle and loss of your menstrual cycle (known medically as amenorrhea) both suggest that a person could be overtraining or not properly fueling, explains exercise physiologist Stacy Sims, CSCS, PhD.
“Having a natural cycle helps you keep track of how well your body is adapting to your training regime,” she says. “If you are adapting properly, you won’t have any menstrual cycle disruption [as a result of exercise].”
2. May impair muscle growth
Popping birth control pills may pause your pump, per research. One 2021 study in the Journal of Strength and Conditioning Research found that oral contraceptive use may minimize muscle gains. For the study, researchers examined the effect of birth control pills on the resistance training outcomes of 72 women, ages 18 to 29, half of whom were on the pill and half of whom were not. The researchers tested the subjects body composition (ratio of body fat to lean muscle mass) and hormone levles before and after putting the subjects through 10 weeks of resistance training.
They found that those taking birth control pills had higher levels of the stress hormone cortisol and significantly lower concentrations of the hormones DHEA, DHEAS, and IGF-1 (all of which play a role in muscle growth), than those not on the pill. Specifically, those who were taking birth control pills that contained a synthetic version of progesterone (called progestin), gained just over half a pound of lean muscle mass over the 10-week study, compared to 3.5 pounds of muscle gained by those not on the pill.
However, and this is important, there was no difference in strength gains with that increased muscle mass vs. the smaller muscle mass gain, notes Dr. Sims. Still, the loss of additional muscle mass may be detrimental to my Olympic lifters and others trying to be strong in a weight category, she says.
3. May reduce or hinder cardiovascular capacity
It’s not just strength athletes whose performance can be impacted by oral contraceptives—endurance athletes can experience adverse side effects, too. “Research suggests that oral contraceptives may be associated with lower VO2 max, which is a measure of the amount of oxygen you can use during training,” says Laura DeCesaris, DC, a functional medicine consultant and powerlifter.
In general, the more intense your workout, the more oxygen your body needs to keep you powered. So, if your V02 max is lower, you won’t be able to go as hard or as long in your workouts, she explains.
Why hormonal birth control pills aren’t always bad for athletes
“There is still some uncertainty on this topic,” says Dr. DeCesaris. Most of the studies looking at the impact of the pill on performance have been quite small, she notes. Plus, many studies are examining multiple types of oral contraceptives, rather than zeroing in on pills with similar hormone profiles, she says.
“Furthermore, every person responds differently to oral contraceptives based on their unique physiology,” says Dr. DeCesaris. “Some people may not notice any detrimental impact to their performance, while others may experience unwanted negative impacts.”
In short: “It’s hard to make blanket statements about how much the pill interferes with athletic performance,” she says.
I’m an athlete. What birth control option is right for me?
Ultimately, you and your healthcare provider may decide that a hormonal birth control does make sense for you. After all, its impact on athletics is just one factor to consider when choosing a contraceptive, says Dr. Sims.
Still, it’s important that you understand that the birth control pill isn’t your only option. “There are so many ways to prevent pregnancy if that’s the sole reason you’re on the pill,” says Alisa Vitti, founder of FLO Living and author of Woman Code and In the FLO.
One option would be to get a progestin-only or copper IUD, says Dr. Sims. “Generally I recommend the progestin-only IUD because there are minimal systemic effects and more people resume natural ovulation six to eight months after initial insertion, which allows them to track their menstrual cycles through basal body temperature,” she says.
Another option would be to combine ovulation tracking with either a barrier method (internal or external condoms) or other pregnancy prevention protocol (Phexxi, diaphragm, cervical cap, for example) during ovulation since it’s the only time of your cycle that you can get pregnant, Vitti says.
Most important, says Dr. Sims, is to talk to your provider about all of your goals. Rather than just sharing that you want to prevent unwanted pregnancy, you should also share your strength and/or endurance targets so you can choose something that helps you achieve all of your aims and gains.