How Bad Is It Really to Do a High-Intensity Workout While You're on Your Period?

Maybe you learned early on that it was a good idea to lay low when Aunt Flo pays a visit. Or maybe you're among the 88 percent of people who have experienced pain during a period, according to a 2017 YouGov poll, and you don't feel up to getting your cardio on.

Either way, you're in the majority: In a March 2019 joint survey from St. Mary's University in England, the workout app Strava and FitWomen, a period tracking and exercise app, 69 percent of the women surveyed said they alter their exercise routine when they're surfing the crimson tide (despite the fact that 78 percent said exercise relieves menstrual discomfort).

How exactly do your hormones affect your athletic performance? Does working out improve PMS symptoms or aggravate them? Can going gangbusters on your Peloton at that time of the month ever be harmful? These answers, and more, below.

It turns out that the hormonal fluctuations you experience during your 28-day cycle can influence whether you're slaying it in cycling class or totally dragging.

On the first day of your cycle, the day your period starts, your estrogen and progesterone bottom out, and as a result, you might not be at your peak, according to the U.S. Department of Health and Human Services Office on Women's Health (OWH). But over the next 12 to 14 days, those hormone levels begin rising.

"This is when women's athletic performance is at its greatest," says Tamika Cross, MD, a Houston, Texas-based ob-gyn and assistant professor of general obstetrics and gynecology at the University of Texas McGovern Medical School.

A February 2017 study in the ​Journal of Clinical and Diagnostic Research​ found that women exhibited significantly greater strength and less fatigue during the follicular phase of their cycle, which starts on the first day of your period and lasts until right before ovulation.

"Your period is a part of your reproductive cycle, and we need to normalize it more. You don't have to change your life or your workout unless you feel like it."

Because you may be feeling stronger, the first two weeks of your cycle are optimal for resistance training. "The shift in hormones make you feel like you're at the top of the world, so lifting weights will be less of a struggle and you may be able to lift slightly more," says Liz Smith, certified personal trainer and co-founder of RebelMOM.

According to the OWH, estrogen peaks during ovulation and then plummets right afterward, which might leave you feeling sluggish during the luteal phase of your cycle, the two or so weeks after ovulation. "Your physical stamina is at its worst during the five or six days prior to your period," Dr. Cross says. Hello, PMS.

Whether you decide to do HIIT or take it easy with some yoga, you don't necessarily need to modify your workout during your period. Although there are no negative side effects associated with exercising during this time of the month (and plenty of positive ones — more on that soon), you might not be down for a serious sweat session.

"I always recommend you listen to your body, so if you don't feel like doing the same workout you normally would, then take it easier," Dr. Cross says. "A high-intensity workout during your period might make you more fatigued than usual, especially if you're going above and beyond your typical repertoire, but there is no medical reason why you can't do it."

When you have your period, Smith suggests sticking to this schedule: Do 30 to 45 minutes of moderate to intense activity for two days, followed by one day where you keep things low-key. Think: a brisk walk, a relaxed bike ride, Pilates or yoga.

Dr. Cross also points out that period-induced cravings for carbs and starchy foods can contribute to tiredness and make you more prone to crashing post-workout. But don't throw in the towel just because you're feeling blah. "A focus on [healthy] eating may mitigate fatigue," Dr. Cross says.

Sometimes all you want to do is R&R on your couch with a bag of Pirate's Booty. We so feel you, but moving will give you a lift. "It sounds counter-intuitive, but many menstrual symptoms can actually be reduced with exercise," Dr. Cross says. That's true if you're doing light, moderate or heavy-duty activity.

In the St. Mary's University survey, 78 percent of women reported that working out helped period-related discomfort, including stomach cramps, sore breasts, moodiness, fatigue and cravings. Score for exercise!

"Endorphins are feel-good chemicals released during exercise," Dr. Cross says. "They can help even out mood swings and make you feel better overall."

Here's how you stand to benefit from working out despite period discomforts:

• ​You might reduce cramps.​ "That's because working out may decrease prostaglandins — compounds that cause cramping by making your uterine contract," Dr. Cross says.
• ​You could ease bloating.​ "It's normal to gain a few pounds during your period due to water retention," Dr. Cross says. "Working out and sweating releases some of that." Just remember to keep drinking plenty of H2O so you stay hydrated.
• ​You'll get an energy boost.​ Even though you might feel exhausted, getting your fitness fix can actually increase your energy. "In addition to the boost you get from endorphins, exercise also helps you sleep better, which will make you more alert," Dr. Cross says. You might have to push yourself for the first 10 minutes or so, but then the endorphins will start flowing and you'll get into the groove.

Unless you have fibroids, it's not bad at all. "Many people think you have to be more sedentary during your period, but in fact, most of us feel better after working out," Dr. Cross says. "Your period is a part of your reproductive cycle, and we need to normalize it more. You don't have to change your life or your workout unless you feel like it."

Athletic performance and stamina are highest during the first 12 to 14 days of a menstrual cycle due to rising estrogen and progesterone levels. You might be feeling sluggish about five to six days prior to your period, so you may want to alter your workouts then — but the key is to keep moving.