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Does Running Cause Loose Bowels?

author image Marissa Baranauskas
Based in Perry, Ohio, Marissa Baranauskas is a Division I and cross-country athlete specializing in articles covering distance running and general fitness. Baranauskas is a certified personal trainer and is pursuing her bachelor's degree in exercise physiology at the University of Akron.
Does Running Cause Loose Bowels?
A group of marathon runners. Photo Credit Tibor Nagy/iStock/Getty Images

Runners seem to be afflicted with stomach-related issues, such as cramps and loose bowels, more than other athletes. According to Suzanne Eberle, author of "Endurance Sports Nutrition," at least 19 to 26 percent of marathon runners have had a sudden urge to make a bowel movement while running. The bouncing motion of a running stride is a known culprit along with certain dietary factors. There are certain precautions you can take to avoid making a hurried stop at the toilet during your next run.

Causes of Diarrhea

Diarrhea occurs when ingested food and fluids pass too quickly or in large amounts through the colon. In normal circumstances, the colon absorbs liquids from food to create a semi-solid stool, but under these conditions, too much water remains in the feces. The bouncing motion of running expedites the process of bowel movements passing through the colon, which may prompt the production of frequent, loose stools. Other factors, including diverted blood flow to exercising muscles and certain fluids and foods, may also contribute to intestinal problems during exercise.

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Fluid Intake

Drink plenty of fluids before running to avoid dehydration, which slows down the body's ability to digest food. According to Suzanne Eberle, prolonged exercise diverts blood flow away from the colon to working muscles, inhibiting digestion. In a dehydrated state, lower blood volume further enhances digestive problems by making less blood available to the large intestine. Avoid warm fluids that contain caffeine, artificial-sweeteners or sports drinks that contain a high carbohydrate content directly before exercise.

Loose Bowels and Diet

Certain foods, such as high-fiber foods and dairy products, take longer for your stomach to digest and are likely to cause problems if consumed too close to exertion. Aim to eat meals one to two hours before running. Insoluble fiber, found in most whole-grain products, should be avoided, as it acts as a stool-softener and promotes bowel movements. Dairy products contain the sugar lactose, which is more difficult for some people with digestive sensitivities to break down and may upset the stomach.

Preventitive Tips

Keep a diary of what you consume before running, taking note of the problem foods that produce bowel movements during activity. Stick to foods that you know are harmless before important workouts or races to avoid potential problems. Wearing loose clothing during a run might also help to alleviate pressure on the intestines. Consider talking to your doctor about taking a prescription anti-diarrhea medicine before races if the problem remains consistent.

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