When it’s that time of the month, you can expect your period to influence tons of things from what you wear to what you eat, and even your running performance. But that doesn’t mean it has to negatively affect your miles—you can use it to your advantage.
“Your period is not a time to hide,” says Stacy Sims, Ph.D., senior research fellow at the University of Waikato in New Zealand, and author of ROAR: How to Match Your Food and Fitness to Your Unique Female Physiology. “It’s a time to hit those personal bests.”
Sims explains exactly why your menstrual cycle can lead to better run outcomes: “Your levels of estrogen and progesterone are at their lowest during your period, which means your pain tolerance and time to fatigue increase,” Sims says. “And your body can tap into more carbohydrate stores, helping you recover faster than when your hormones are higher.” She explains that this low-hormone phase—a.k.a. your period—is actually a great time to go hard in your workouts, as long as you’re feeling up to it.
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But of course, every woman is different. And if your cramps ever kept you curled up on the couch all afternoon, you know that your period hardly guarantees a PR. What’s most important is listening to your body and doing what’s best for you.
Here, we address some common period concerns—including whether you burn more calories on your period—to help you prep for optimal performance, no matter what your uterus is up to.
Do you burn more calories on your period—or carbs?
Some period benefits are overstated—or flat-out wrong. For one, you don’t burn more calories on your period, contrary to some locker room chatter. If anything, Sims says you burn slightly more calories when your hormones are higher (known as the post-ovulation luteal phase) because your heart rate, respiratory rate, and core temperature increase. “It’s very minimal though,” she says. “Approximately 100 calories per day.”
Also, when it comes to carb-loading on your period, one study notes there can be a tiny window when your estrogen levels are higher and your ability to store glycogen may therefore be greater. But, the study found that this doesn’t make much of a difference if your carb intake falls within the recommendations of about 3.5 to 5.5 grams of body weight per day.
So no matter how to look at it, your menstrual cycle can be a trick time, and there are tons of different changes happening in your body that you might have to adjust for—but making up for burning more calories isn’t necessarily one of them.
Why am I experiencing bathroom problems?
The drop in hormones during your period can send you to the bathroom, and not just because you need to change your tampon. “Intestinal movements can be faster or slower, which translates into constipation or loose stools,” says Alyssa Dweck, M.D., a gynecologist practicing in Mount Kisco, New York.
She suggests avoiding dietary triggers, such as sweet and salty foods, and keeping up your running routine; just make sure there are some bathroom stops along your route.
How can I manage my cramps?
Like a lot of women, you might have cramps at the start of—or throughout—your period because “your uterus contracts to help expel its lining,” according to the Mayo Clinic.
An easy run could actually help. “Endorphins are your body’s natural painkillers, so you could feel better if you power through your cramps,” Dweck says. If you can predict when they’re coming (try a period-tracking app like Flo), she says to take Advil or Motrin in advance of your period to get ahead of the problem.
Is it normal to miss a period?
It’s common among athletes, but it’s not a good thing. “Your period is a vital indicator of wellness,” says Kirstin Leitner, M.D., an assistant professor of clinical obstetrics and gynecology at Penn Medicine. So, if it disappears—which is known as amenorrhea—it’s often caused by excessive exercise, low body weight, or not taking in enough calories to fuel your performance and your life. If you don’t get your period, it’s smart to make an appointment with your ob-gyn ASAP. (Amenorrhea may affect up to half of female athletes at some point.)
Aside from fertility issues, missing your period can lead to a decrease in bone density (caused by low estrogen), particularly if your period goes MIA for too long. This then puts you at a higher risk of injury, Leitner says. Indeed, high school athletes with irregular periods were more likely to experience a severe injury than girls with normal periods, per a Journal of Athletic Training study.
The other end of the spectrum isn’t so great, either: “If you’re soaking through two tampons or pads an hour, you might be at risk for anemia,” Dweck says. Look out for weakness and shortness of breath, and a see a doc if your heavy periods persist month after month.
How can PMS affect performance?
You might notice a dip in your mood and motivation the week before your period, which is totally normal. PMS is, in fact, associated with lack of concentration and low motivation, according to an International Journal of Women’s Health study on high school students.
“This is a good time to focus on steady-state runs and higher rep, lower-weight resistance exercises,” Sims says. “Think of your training schedule as a monthly cycle. Give yourself the flexibility to push hard when you’re feeling good and to back off when you’re not.”
Kiera Carter has a decade’s worth of experience covering fitness, health, and lifestyle topics for national magazines and websites. In a past life, she was the executive digital editor of Shape and has held staff positions at Fit Pregnancy, Natural Health, Prevention, and Men’s Health. Her work has been published by Marie Claire, Cosmopolitan, Travel + Leisure, and more. She spends her free time boxing, traveling, and watching any movie or show with a strong female lead. She is currently based in New York.
