Diarrhea After Working Out, Explained

Gastrointestinal symptoms can be a common complaint when working out. Symptoms may include diarrhea, heartburn, abdominal pain, or nausea.

Strong woman during an intense workout on abdomen on mat using a ball.
Garage Island Crew/Stocksy

Diarrhea after working out can be an unpleasant side effect of exercise. If you experience this, heartburn, nausea, or any other exercise-induced gut trouble after—or even during—a workout, you are not alone.

These gastrointestinal symptoms are fairly common. Research suggests anywhere from 30-90% of people who exercise experience gut problems from a workout.

Gastrointestinal Changes After a Workout

Exercise can cause a variety of gastrointestinal (GI) symptoms. These symptoms can range in severity and, in some people, can be bad enough to impact athletic performance.

Diarrhea

Up to 90% of long-distance runners and endurance athletes will experience GI symptoms, including diarrhea. Diarrhea among the group during or after their intense exercise is so common that it is sometimes referred to as "runner's diarrhea."

The loose, watery stools should clear up on their own in about 24 hours.

Heartburn

Another common GI symptom that may be associated with exercise is heartburn.

Heartburn occurs when the muscles between the stomach and the esophagus relax, which can allow stomach acid to reach the esophagus. These muscles may relax during exercise, resulting in heartburn.

Eating too close to exercising can cause this to happen, but certain forms of exercise can especially increase your odds of heartburn. More intense exercises like running are more likely to cause heartburn than low-impact workouts like cycling.

Other symptoms

Exercise may also cause other GI symptoms, including:

  • Nausea
  • Cramping
  • Abdominal pain
  • Vomiting
  • Aching in the side
  • Gas
  • Burping
  • Intestinal bleeding
  • Bloating

Why Working Out Can Cause Gastrointestinal Symptoms

There are three main reasons that exercise can cause GI symptoms.

Change in blood flow

During an intense workout, blood flows toward the muscles that are being exercised and away from the GI tract. This results in a lack of blood flow in the GI system, a problem known as intestinal ischemia. This lack of blood flow can cause a number of symptoms, including diarrhea and abdominal pain. Changes in blood flow may be more likely after a strenuous exercise, such as a marathon.

In some cases, runners may experience bloody bowel movements. Some research suggests this symptom may be a sign of ischemic colitis, a condition in which blood flow to the colon is temporarily decreased. It would require further medical attention.

Disruptive movements

Another reason working out may interrupt the GI system is the potential for the jarring movements to cause damage to the intestinal lining. For instance, the movements involved in running could cause diarrhea, a feeling of urgency to have a bowel movement, and in some cases bleeding in the GI tract.

Nutrition

What you eat may play a role in the relationship between exercise and GI symptoms. Some nutrients like protein, fiber, and fat could increase the odds of experiencing GI symptoms when working out. These nutrients take longer to and are more difficult to digest, which could lead to stomach pains, gas, and cramping. Dehydration can also worsen GI symptoms since water helps food pass through the intestine.

Prevention

There are a few ways to reduce the chance of experiencing GI symptoms during exercise.

Since dehydration can cause GI symptoms, drinking fluids before and during your workout to stay hydrated can help avoid a negative reaction.

Some researchers also suggest that avoiding certain forms of food before a workout may help prevent or reduce symptoms. Try to avoid foods that are high in fiber, fat, or protein. And limit the amount of concentrated forms of carbohydrates (like sugary sodas and sweets) you eat before a workout.

Treatment

If GI symptoms like diarrhea do occur during or after a workout, there are ways to help your body recover.

It is important to replace lost fluids and avoid dehydration after experiencing diarrhea.

This can be achieved by drinking:

  • Water
  • Juice
  • Sports drinks
  • Soda that doesn't contain caffeine
  • Salty broth

Once symptoms pass, eating foods that are soft and bland may also help.

Symptoms may also be managed by:

  • Reducing intensity of workouts
  • Trying different forms of exercise (if you're a runner, try cycling or swimming)
  • Using medications under the guidance of a healthcare provider

When to See a Healthcare Provider

If you are experiencing any GI symptoms during or after a workout, you can consider speaking to a healthcare provider—especially if your symptoms happen each time you work out or they prevent you from reaching your exercise goals.

In many cases, symptoms like diarrhea should resolve on their own without medical attention. But you should contact a healthcare provider if you have diarrhea and:

  • It persists for more than two days
  • You are displaying signs of dehydration
  • You have blood or pus in your stools
  • You have tarry or black stools
  • You have a fever of 102 degrees Fahrenheit or higher
  • You have severe pain in the rectum
  • You have severe pain in the abdomen

If you are experiencing heartburn, you should contact a health care provider immediately if:

  • You have black or maroon stools
  • You have vomit that looks like coffee grounds or is bloody
  • You are experiencing a pressure, crushing, squeezing, or burning sensation in the chest (this may indicate a heart attack)

Summary

GI symptoms are a common experience when working out. Symptoms may include diarrhea, heartburn, abdominal pain, and nausea, among other symptoms. These gut problems may be more common in more intense forms of exercise, like long distance running. Most times, the symptoms are temporary and go away on their own.

The symptoms can not only be bothersome, but they can also affect performance. Avoiding certain foods, remaining hydrated, and engaging in less intense forms of exercise may assist in preventing GI symptoms brought on by exercise.

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Sources
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  2. de Oliveira EP, Burini RC, Jeukendrup A. Gastrointestinal complaints during exercise: prevalence, etiology, and nutritional recommendations.Sports Med. 2014;44 Suppl 1(Suppl 1):S79-S85. doi:10.1007/s40279-014-0153-2

  3. Faress A, Masood S, Mian A. 'Runs' from a run: A case of exercise induced ischemic colitis. World J Emerg Med. 2017;8(4):302-304. doi:10.5847/wjem.j.1920-8642.2017.04.010

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