3 Causes of Diarrhea After Exercise and How to Prevent It

Maybe you just finished your weekly leg workout, won a tough paddleball game or completed your daily three-mile jog when, all of a sudden, your stomach starts to churn. Now, instead of sprinting on the treadmill, you're racing to the restroom. ‌Crap‌.

If this describes your post-workout routine, you're certainly not alone. Learn the causes of diarrhea (and general digestive unrest) after exercise and how you can prevent post-run runs.

"The jostling movement of exercise can stimulate diarrhea," Audra Wilson, RD, CSCS, bariatric dietitian at Northwestern Medicine, says. "It literally shakes things around in our digestive tract, which increases the rate of gut motility (the movement of food through the digestive system)." This is actually one of the reasons why exercise can be helpful for folks with constipation.

Still, if you're jumping, squatting and lunging before your food is properly digested and bulk stool formation is complete, you may have loose, runny BMs.

Your diarrhea might be the result of eating something that didn't agree with you. OK — but if that's the case, how come you only see the effects after you hop off the bike?

Your digestion goes on hiatus during a workout. "Blood is diverted away from the GI system to the larger working muscles involved in exercise," Wilson says. "As a result, we have less blood flow to stimulate movement in our digestive tract."

Once you reach the end of your workout and normal blood flow is restored to your digestive system, you may feel the digestive affect of your food insensitivity.

According to the National Institute of Health, irritable bowel syndrome (IBS) includes recurring abdominal pain along with diarrhea and/or constipation. "People with IBS aren't appropriately absorbing the nutrients in the food they eat," Wilson says. "The jostling motion involved in physical activity can exacerbate the symptoms."

What's more, stress can cause digestive unrest for those with IBS, according to an October 2014 study in the ‌World Journal of Gastroenterology.‌ The good news: Exercise can be the perfect stress buster. The bad: If you're nervous about tush fireworks, it can make your symptoms even worse.

"Those who have had an embarrassing bathroom moment after working out might worry that it will happen again," Wilson says. "In people with IBS, this anxiety can actually trigger a physical response of diarrhea or feeling like you have to go."

Certain types of exercise (think: intense or high-impact activities, like running) are more likely to scramble your insides and lead to uncomfortable backdoor action. But before you give up your hardcore workout, hear this: "You don't have to compromise — you can actually train your gut to be able to handle the movement," Wilson says.

Start with shorter bouts of intense exercise and work your way up slowly, increasing the duration of your workout by about 10 to 15 minutes, or 20 to 30 percent every week. Wilson explains that nudging up your tolerance for intensity bit by bit gives your body a chance to adapt.

Certain nibbles might not play well with your GI tract. To figure out what the trigger might be, it's helpful to track what you eat, beginning about 12 hours before working out, as well as your bowel movements.

"Chronic diarrhea is a symptom you don't want to ignore," Wilson says. She suggests tracking foods and BMs using a phone app for convenience. After a few days, scan through your notes, looking for trends or patterns.

According to Wilson, common diarrhea culprits include caffeine (especially coffee), anything fatty or fried and high-fat dairy. Consider steering clear of these the day leading up to a sweat sesh (also the night before if you work out in the morning). Notice if you see an improvement.

Leave a buffer between mealtime and cardio time. "Avoid eating more than a small snack for half an hour prior to exercising to give yourself time to digest," Wilson says. "And don't have fat for two hours as it takes longer to move through your system."

While you should hold off on eating a full meal shortly before hitting the gym, a light bite mid-way through your workout can actually calm a turbulent tummy. "It will help make sure your GI tract is running smoothly and keep your digestion moving at a steady pace," Wilson says. "Simple carbs stimulate digestion and give your gut some bulk to form stool, without taxing your body."

Her suggestions: an electrolyte drink or goo, jelly beans, a protein or granola bar, a banana chunk or graham crackers.

Despite your best efforts, you're still camping out on the porcelain post-workout. Ease your indigestion with these moves.

Sip your water slowly throughout your workout and make sure to rehydrate after exercise. When it comes to dehydration, post-workout diarrhea packs a double whammy: Not only do you lose fluid when you sweat during exercise, but diarrhea can make you even more parched. Refill that water bottle — or better yet, grab an oral rehydration solution like Pedialyte, Wilson recommends.

Stick to a bland foods for your next meal or until your diarrhea has resolved. The gentle-on-your-tummy BRAT diet — which stands for banana, rice, applesauce and white toast — will slow down your gut motility and give your GI tract a chance to create bulk in the stool. (Just don't stay on the BRAT diet for longer than necessary, as it's low in nutrients and can cause constipation.)

Loperamide is the active ingredient in over-the-counter treatments like Imodium A-D. According to the National Library of Medicine, it works by decreasing the amount of liquid flowing to the bowel and slowing down the movement of the bowel so that your body has a chance to form solid stool.

One important note: Loperamide can be dehydrating, so it's best not to take it immediately after intense, sweaty workouts. Make sure you're rehydrating before you try any anti-diarrhea medications and consult your doctor.