Exercise-Related Diarrhea and Loose Stools

Runner's Trots Strike During and After Workouts

Starting Line Portajohns - Vancouver USA Marathon
Starting Line Portajohns - Vancouver USA Marathon. Wendy Bumgardner ©

Do you have problems with loose stools or diarrhea during or after a workout? This is so common that it has a cute name, runner's trots. Walking and running are good exercises for maintaining regular bowel movements. This is one theory on why there is a decreased incidence of colon cancer among those who walk and run. However, they can also be too much of a good thing.

You're Not the Only One with Exercise-Related Diarrhea

An estimated 20 to 50 percent of distance runners have runner's trots, with a range of symptoms from cramping and nausea to bouts of flatulence and diarrhea during or after their workout.

Walkers, especially those who walk at a high heart rate, can discover this same effect.

Causes of Runner's Trots

A single cause of exercise-related diarrhea hasn't been definitively identified. Runner's trots may be caused by different factors in different people. One theory is that the simple up and down jostling of the body stirs the bowels. Blood flow to the intestines is diverted to your legs and that may cause the cramping and diarrhea.

Underlying irritable bowel disease may be brought to light by the additional stress of exercise. Dehydration on long walks and runs can also cause diarrhea. Lactose intolerance effects might be enhanced by the exercise.

Symptoms of Exercise-Related Loose Stools

You may experience any of these: cramping, nausea, flatulence, diarrhea during or after your workout. It can produce painful cramping and an extremely urgent need to defecate.

How to Prevent Exercise-Related Diarrhea and Loose Stools

  • Avoid eating for the two hours before your workout. The presence of food in the stomach may make things worse or set it off.
  • Avoid caffeine and warm fluids as they can speed up the movement of wastes through the intestines.
  • Limit dairy products or use Lactaid when enjoying dairy products, especially if you know you are lactose-intolerant.
  • Limit high-fiber foods in the days before a long race. Save the beans and roughage for future healthy meals.
  • Avoid any other foods that you know produce flatulence or loose stools for you. Foods to Avoid for Loose Stools
  • Drink plenty of fluids. It is best to drink a full 16 ounces. of water an hour before your workout, giving the excess fluid time to pass through. This way you will start off well-hydrated but without excess urine production right when you get going. Drink 8 ounce of water every 15 minutes while walking, running, or doing a workout.
  • Know your bowel habits and try to schedule your workouts for immediately after your usual bowel movement times.
  • Use these low residue diet tips the day before a race or long walk.
  • If all other precautions fail, for races or special walks where you know toilets will not be readily available, use an over-the-counter anti-diarrhea product such as Imodium. Studies have shown this reduced the problem in 70 percent of triathletes prone to exercise-induced diarrhea. How Safe is Imodium?: the answer is, very safe.
  • Design your walking and running routes to include a restroom stop at the time when diarrhea usually hits. If you develop the urgency a half hour into your walk or run, plan your route accordingly.
  • Be prepared with what to do if there are no toilets available. You don't want to end up arrested for indecent exposure or public nuisance.
  • Have a medical check-up for irritable bowel syndrome and be open in discussing your problem with your medical provider. While these details might be embarrassing, you will only get a good diagnosis by giving a full and frank history. Keep notes on your episodes of runner's trots so you will have good data to give your doctor.


de Oliveira EP, Burini RC. "The impact of physical exercise on the gastrointestinal tract." Curr Opin Clin Nutr Metab Care. 2009 Sep;12(5):533-8.

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