Why Does Running Make You Poop?

fit woman taking a break from running outside in the cold
Why does running make me poop? All that pounding and movement causes contractions in your colon.
Image Credit: martin-dm/E+/GettyImages

You're partway through a soul-cleansing jog, wind against your cheeks, feet slapping the ground in perfect tempo to your favorite fitness playlist. Then, all of a sudden — ​oh, crap​. You have to poop.

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If your bowel movements frequently seem to coincide with workouts — welcome to the club. "It is very common," says Todd Buckingham, PhD, lead exercise physiologist for Mary Free Bed Sports Rehabilitation. "Upwards of 80 percent of runners have experienced GI distress at some point."

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So why does running make you poop? Here, Todd talks us through what causes running poop, plus tips to rein in those pesky tootsie rolls.

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3 Reasons Running Makes You Poop

1. You’re All Shook Up

The thudding, pounding, up-and-down jolts that running sends through your body can trigger the urge to defecate.

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"With each foot strike, you shake and jostle your internal organs, speeding up the descent of poop," Buckingham says. "It causes spasms and contractions to occur in the colon and rectum, which can make you more susceptible to bowel movements."

Joggers are more prone to this effect than other athletes. "Running is more physically jarring than other sports, such as cycling or swimming," Buckingham says.

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2. Adrenaline Is Coursing Through You

When you exercise (or even ​think​ about exercising, for that matter), your brain releases the hormone adrenaline, also called epinephrine. Adrenaline increases your heart rate, delivering extra blood flow to the muscles at work so you can perform with greater speed and strength. All good stuff — except it can also lead you to drop a deuce.

And if you're running in an actual race, anticipate a much higher output of adrenaline — and a greater chance you'll have to take a bathroom break — than during your everyday trot. Known as the "fight or flight" hormone, adrenaline also surges when you're under stress.

Although there is no solid scientific evidence illuminating why adrenaline leads to defecation, there are speculations.

"One theory postulates that in prehistoric times when cavemen were running from saber tooth tigers, adrenaline caused them to defecate so that they would be lighter and able to get away faster," Buckingham says.

3. Your Digestion Is on Slow-Mo

Exercise alters the passage of blood flow through your body. "Your blood flow diverts to wherever oxygen is most needed," Buckingham says. "So if you're running, more blood goes to your legs, while the amount that heads to your GI system is limited."

As a result, the rate at which you digest slows down compared to when you're at rest. You might assume that slower digestion would make you less likely to defecate, but in fact it ups your chances of diarrhea because your GI system can't function as efficiently.

"In addition, the hormones churned out during exercise cause more water to be released into your digestive system," Buckingham says. "This causes the bolus [of chewed up food] to be more liquid, leading to loose stool."

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6 Ways to Avoid Pooping on a Run

First up, there's nothing wrong with a mid-run poo. "Other than it being inconvenient and perhaps uncomfortable, it is not detrimental to your health in any way," Buckingham says. Still, if it's getting your panties in a twist, you can try a few of these tips.

1. Keep a Food Diary

"Certain foods — including dairy, artificial sweeteners, gluten and soy — can contribute to GI distress," Buckingham says.

Jot down what you're nibbling on the day of a run can help you understand "why does running make me poop" and how your diet might be influencing your bowel movemnts. And in general, don't eat for two to three hours before exercising.

2. Avoid Java Before a Jog

Caffeine — and coffee in particular — might explain why does running make you poop. "Chemicals in coffee trigger gastric emptying," Buckingham says. Finish your cup of joe at least one hour before your run so it can make its way through your stomach.

3. Make Time for a Warm-Up

Prior to sprinting down the road, spend between two to five minutes getting your heart rate up at home.

"Do dynamic stretching drills that involve light movement, like butt kickers or jumping jacks," Buckingham says. "Bouncing up and down and shaking things up can induce a bowel movement before your run so you don't have to stop during."

4. Plan Your Route Strategically

Ironically, worrying about having to take a dump can make you more likely to need a potty break, because stress increases adrenaline output. To quell your nerves, plot out your run.

"Make a point to pass by a gas station or loop back home partway through," Buckingham says.

5. Steer Clear of NSAIDs

Pain relievers like ibuprofen and aspirin can lead to an upset stomach — and running poop. Wait until after your workout to take an NSAID.

6. Play It Safe on Race Day

If you're running competitively, from a 5K to a marathon, follow these guidelines to keep pooping in check.

"Fat and fiber are difficult to break down, so decrease your intake two to three days prior to a race," Buckingham says. "Instead, carb-load with foods like white pasta or white bread and jam."

And prepare as much as you can in advance, deciding ahead of time everything from what you'll wear to how you'll get there. "To minimize adrenaline release, don't try anything new on race day," Buckingham says.

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