How exercise affects your menstrual cycle

Let’s say you recently started an intense exercise program. You’re working out nearly every day, running or biking more miles than ever before.

At first, your period is late. Then you start skipping a few periods altogether. You know you’re not pregnant or close to menopause.

You wonder: Is this normal? How much exercise causes a missed period? And how long can exercise delay your period? Is it just a result of your new training schedule, or something more serious?

People can have irregular periods for many reasons. But ultimately, missing periods because of extreme exercise isn’t healthy. It can have both short-term and long-term health effects.

So, how much exercise causes a missed period? It’s a complicated answer but important for every person who ovulates to understand. It’s also a good idea to understand how energy levels fluctuate during any given menstrual cycle.

What to Know About Exercise and Missed Periods

The term for when someone who isn’t pregnant or menopausal misses three or more periods is secondary amenorrhea. (Primary amenorrhea is when someone assigned female at birth has not gotten her first period by age 15.)

Exercise alone won’t cause you to miss periods. Rather, it’s the combination of exercise and not eating enough.

A study in Endocrinology and Metabolism looked at the relationship between calories, exercise, and periods. The study focused on women 18 to 30 years old. Researchers found that a deficit of 470 to 810 calories a day over three cycles was enough to cause period disturbances.

Exercise causes you to burn more calories than your body normally does. If you burn more calories than you eat, you create an energy deficit.

If you have excess fat, your body will use this stored fat to make up the energy deficit. This is, of course, how basic weight loss works.

But if you have a calorie deficit and you don’t have much stored fat, the deficit can become too large. Without enough fuel month after month, your body starts to compensate.

One way it compensates is by shifting energy away from certain bodily functions, like reproduction. So, when your body doesn’t have enough fuel, your brain will send a signal to your ovaries to stop ovulating. Without ovulation, you won’t have a period.

Women can do intense amounts of training and exercise without losing their period. The problem happens when they are not replenishing their energy,

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Why Is Amenorrhea Unhealthy?

Missing periods when you’d normally have them (i.e., you’re not pregnant, breastfeeding, perimenopausal, or menopausal) is a possible cause for concern. Over time, this can lead to a number of problems.

First, amenorrhea may signal that you have an eating disorder. It is also a possible warning sign of female athlete triad syndrome.

Female athlete triad syndrome is a combination of:

  • Disordered eating, including anorexia, bulimia, or obsessively avoiding eating certain foods.
  • Amenorrhea, which results in the delaying of one’s first period past the age of 15.
  • Low bone density, which increases the risk of stress fractures and broken bones.

Secondly, amenorrhea is not a sign of peak physical fitness.

Though athletes may increase exercise and reduce calories to improve their performance, the opposite can happen. If you’re restricting calories so much that you’ve stopped menstruating, it means your body doesn’t have enough fuel to function optimally. Ultimately, you can damage your heart and reproductive system.

This is why seeking care is important if you suspect a connection between your missed periods and your exercise and eating habits. A sports medicine doctor can connect you with the right treatment and resources. Your gynecologist or primary care doctor can also help.

Can Strenuous Exercise Cause Breakthrough Bleeding?

Some athletes have reported breakthrough bleeding after strenuous exercise. Breakthrough bleeding is bleeding that happens outside of the menstrual cycle. But exercise alone shouldn’t cause bleeding.

If you have breakthrough bleeding after strenuous exercise, don’t panic. But also: Don’t ignore it — especially if it happens more than once.

It may have something to do with your uterine lining. Exercise can cause pressure and irritate any endometrial or cervical polyps you may have. Thyroid issues and certain kinds of birth control may also cause breakthrough bleeding with or without exercise.

See your gynecologist if breakthrough bleeding is a persistent problem for you, especially bleeding related to exercise.

Can Exercise Help With Menstrual Cramps?

You may have heard that exercise can help with cramps and other menstrual symptoms. There has been some research on this, though it’s inconclusive. For some women, exercising during their period leads to fewer menstrual cramps.

But others may have periods so painful that the thought of exercise seems impossible. This is especially true for those who have a condition like endometriosis. If you have endometriosis and you’re dealing with debilitating cramps, talk to your gynecologist.

Does Syncing My Menstrual Cycle With My Exercise Have Benefits?

In 2019, U.S. women’s soccer performance coach Dawn Scott told Good Morning America that period tracking was among their winning strategies. Team members reportedly started tracking their periods a year before the World Cup.

Many players noticed they were more fatigued on the first day of their cycle. They changed their workout schedule accordingly. They took more recovery time during certain times in their cycles.

Scott said that paying attention to details helped players perform better.

So, can adjusting your exercise based on your cycle (also known as “cycle syncing”) really increase your performance? Maybe. But trying to gather the data and time workouts isn’t necessarily feasible for your average person.

Still, hormone levels change throughout your cycle and can impact your energy. Having a general understanding of what this looks like for many people can help.

  • Day one of your cycle: This is when estrogen and progesterone levels are at their lowest. They slowly rise over the days that follow.
  • Week two of your cycle: During this second week, you may notice that your energy levels go up. Estrogen increases to prepare for ovulation. (Ovulation is when your ovary releases an egg.)
  • Week three of your cycle: For most people, this is when ovulation happens and when estrogen levels peak. Immediately after ovulation, estrogen levels fall again — which can make you feel sluggish. However, you might find that exercising during this time can help boost mood and increase energy.
  • Week four of your cycle: As your next period gets closer, your estrogen and progesterone levels both fall. This is when many women start to feel premenstrual symptoms. Exercise may help.

Many apps can help you track your menstrual cycle (though take care not to share personal health data). You can also keep a written tracker, noting how your energy levels change.

ACOG. Amenorrhea: Absence of Periods. Link

Endocrinology and Metabolism. Magnitude of daily energy deficit predicts frequency but not severity of menstrual disturbances associated with exercise and caloric restriction. Link

Frontiers in Endocrinology. Bone health in functional hypothalamic amenorrhea: What the endocrinologist needs to know. Link

The New York Times. Cycling Synching is Trendy. Does It Work? Link.

Office on Women's Health. Physical Activity and Your Menstrual Cycle. Link.

Runner's World. Ask the Coaches: Vaginal Bleeding. Link

About UPMC Magee-Womens

Built upon our flagship, UPMC Magee-Womens Hospital in Pittsburgh, and its century-plus history of providing high-quality medical care for people at all stages of life, UPMC Magee-Womens is nationally renowned for its outstanding care for women and their families.

Our Magee-Womens network – from women’s imaging centers and specialty care to outpatient and hospital-based services – provides care throughout Pennsylvania, so the help you need is always close to home. More than 25,000 babies are born at our network hospitals each year, with 10,000 of those babies born at UPMC Magee in Pittsburgh, home to one of the largest NICUs in the country. The Department of Health and Human Services recognizes Magee in Pittsburgh as a National Center of Excellence in Women’s Health; U.S. News & World Report ranks Magee nationally in gynecology. The Magee-Womens Research Institute was the first and is the largest research institute in the U.S. devoted exclusively to women’s health and reproductive biology, with locations in Pittsburgh and Erie.