Changes Exercise Has on Your Period

Breakthrough Bleeding, Missed Periods, Flow Changes, and Pain Effects

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There are many changes in your body that you can expect to happen when you start to exercise regularly. You may have sore muscles, lose weight, sleep better, and gain strength. But what you might not expect is that regular exercise can cause changes in your menstrual cycle too. The changes may be subtle or extreme depending on many individual factors that influence how your body reacts to your increased activity level. Here are the four most common effects exercise can have on your period.

how exercise affects period
Illustration by Brianna Gilmartin, Verywell

Random Bleeding Outside of Your Regular Period

When you have vaginal bleeding during your menstrual cycle that is not during the week of your regular period it is called breakthrough bleeding. It typically happens because your uterus is getting mixed up hormonal messages. Breakthrough bleeding is a common type of abnormal uterine bleeding.

Regular exercise can cause subtle changes in your hormone levels that interfere with the cyclic buildup and shedding of the lining of your uterus. The lining of your uterus may respond to these mixed up signals by randomly shedding, which causes the breakthrough bleeding. This bleeding may be dark or bright red. Typically it is just spotting or a flow lighter than your typical period. You may also experience breakthrough bleeding during or immediately after strenuous exercise.

There is no direct cause and effect of bleeding after exercise. It could be the result of a disordered endometrium. Or, it could be due to structural changes in the lining of your uterus or on your cervix. It is speculated that the increase in abdominal pressure associated with some types of exercise may cause bleeding from submucosal uterine fibroids, endometrial polyps, and cervical polyps.

Missed Periods

Even though it is good for you, exercise puts some stress on your body. The physiologic stress of exercise can interrupt the balance in your hypothalamic-pituitary-ovarian axis. The hypothalamus is a structure in your brain that acts as the control center for your menstrual cycle. It sends hormonal messages to your pituitary gland and your ovaries that trigger your ovulation.

If this communication gets interrupted as the result of a physiologic stressor, like strenuous exercise or significant weight loss, you will not ovulate. If you do not ovulate, the changes that trigger your menstruation will not happen and you will miss your period.

Missing your periods because of strenuous exercise is called exercise-induced amenorrhea.

An extreme form of exercise-induced amenorrhea is known as the female athlete triad. The female athlete triad describes a specific condition in adolescent and young female athletes that consists of:

  • Menstrual dysfunction
  • Low caloric intake
  • Low bone mineral density

The combination of intense strenuous exercise and low caloric intake puts a very significant stress on the young athlete's body. In response to this physiologic stress, the hypothalamus (the menstrual control center in the brain) turns down its stimulation of the ovaries. Eventually, ovulation does not occur so the athlete's periods stop. Over time, her ovaries slow down hormone production. Her estrogen levels drop, which causes bone loss along with other negative health outcomes.

Change in Your Flow

Don't be alarmed if you notice that your periods become a bit lighter once you start a regular exercise routine. The same hormonal changes that can stop your periods altogether can exert a weaker effect on your body and just cause a lighter flow.

Another possible change that may contribute to a lighter flow is the moderate weight loss that can come with regular exercise. Body fat or adipose tissue actually produces a type of estrogen. Excess estrogen in your body can cause the lining of your uterus to build up more during the first half of your cycle. The thicker the lining, the heavier your menstrual flow. With weight loss, you in effect decrease the amount of estrogen in your body, which in turn decreases the cyclic build up of the lining of your uterus. A thinner lining means a little flow.

Period Pain

There are two distinct types of period pain. Whether exercise helps or not depends on the cause of your pain.

Primary dysmenorrhea is a painful period with no identifiable underlying cause. It usually starts with your very first period and then the pain comes with each subsequent period. Often it goes away by the time you are in your 20s. It is likely that exercise can help reduce this type of painful period.

It is thought that the subtle hormonal changes associated with regular exercise may decrease the concentration of prostaglandins in the lining of your uterus. Prostaglandins are inflammatory substances produced in your body that are responsible for causing uterine muscle contractions and cramps. That is why pain medications that block the production of prostaglandins like ibuprofen an NSAID work best to treat menstrual cramps. Decreasing the concentration of prostaglandins decreases period cramping. However, clinical studies of this hypothesis are few and have not been robust enough to reach a conclusion as to whether exercise helps or not.

Secondary dysmenorrhea is a painful period that results from an underlying pathology. This type of period pain usually develops over time and may not start until at least your 20s or even later. Two common conditions that cause this type of period pain are:

Exercise might help to reduce painful periods by its effects on prostaglandins if you have secondary dysmenorrhea. Just like with primary dysmenorrhea, prostaglandins play a major role in causing uterine contractions and cramping even with an underlying pathology.

However, do not be alarmed if you have increased pain when you exercise during your period, especially if you have uterine fibroids. Uterine fibroids are tumors that grow from the smooth muscle in the wall of your uterus. Fibroids develop a network of blood vessels because (just like all other structures in your body) they need blood and nutrients to grow.

When you exercise, you shift your blood flow to favor your heart, lungs, and your muscles, subtly shifting blood away from other structures not involved in exercise, including your uterus. Under normal circumstances, your uterus adapts to this without any problem. But if you have fibroids, it is possible that they might have a significant decrease in blood flow during exercise.

This causes a condition known as ischemia which is similar to what happens in heart muscle before a heart attack. When a muscle becomes ischemic, you feel it as pain.

If you have significant fibroids it is likely you will have an increase in uterine pain and cramping when you exercise during your period because of ischemia.

A Word From Verywell

For the most part, some breakthrough bleeding or an occasional missed period is not a big concern if you have just started exercising, are exercising intensely, or have just lost a lot of weight. But if you have a change in your cycle that continues for two to three months in a row, you should discuss it with your healthcare provider.

Overall, exercise has positive effects on your period. It is interesting to note that women who are sedentary and do not get regular exercise typically have heavier and more painful periods. Get moving. After all, who wouldn't want a lighter period with less cramping? 

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