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In a lightly wooded area next to a running path. In a stranger’s bathroom. One hundred meters from the finish line. These are just a few of the places the runners we approached admitted to, well, crapping out during a run. And we don’t mean figuratively. Yep, it’s time for that conversation: pooping on race day.

We took a look at the link between running and pooping to help you avoid any difficult butt situations right before that all-important mid-marathon IG snap.

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Image by Dana Davenport

Yeah, it’s an awkward topic. (Go ahead and get out your giggles.) But anyone who runs or exercises regularly knows that unpredictable bowel movements are just part of the deal. They can come on quickly without warning, slowly and painfully, or sometimes not at all.

So what’s really going on?

Being more mobile makes your GI tract more active

Put simply, working out increases movement in your GI tract, says gastroenterologist Jeff Crespin, MD: “When you exercise, there’s more stimulation, which increases upper gastric motility. This carries over to the lower gastrointestinal tract.”

Translation: The more you move, the more you poop.

Robynne Chutkan, MD, a gastroenterologist and the author of Gutbliss, says our GI tracts are muscular structures not unlike the large muscles of our arms and legs.

“Exercise stimulates peristalsis — the series of concentric contractions that moves the products of digestion through our intestines,” Chutkan says. “For some people, it can result in an urge to have a bowel movement as the intestinal contents reach the rectum — or the end of the road, so to speak.”

Decreased blood flow to the organs makes a difference

Running long distances can also affect your circulation, which may prompt a desperate mid-marathon toilet search.

Essentially, during exercise, your visceral blood flow decreases, Crespin explains. This means your body directs less blood toward the GI tract to funnel more of that good red stuff to other parts of your body — namely, the peripheral muscles you use for running.

“This decreased visceral blood flow strains the GI tract and can lead to diarrhea,” Crespin says.

H2O = need to go

Your level of hydration can play a role too.

“If you drink a lot of water, your stool is more likely to be soft and moist, finding its way to the rectum faster and making it easier to expel. Or maybe you’re dehydrated and have hard, dry stool that’s difficult to push out,” Chutkan adds.

The timing of those drinks can make a difference, too. If you drink too close to the start of the race, it might soften those stools so that it’s not just you who gets off to a flying start.

Being nervous about mid-race diarrhea can give you mid-race diarrhea


On top of GI changes, race day jitters can contribute to your pooping woes in either direction, says Nancy Clark, RD, a sports dietetics specialist: “If you’re already nervous about getting diarrhea during a race, that can make the problem worse.”

On the other hand, it can also halt the process, Clark suggests, since nerves can cause an increase or decrease in peristalsis depending on the individual.

Constipation during and after a run is also a thing

While the panicky “I need to go right now” feeling is not uncommon mid-run, there’s also the equally scary alternative: not being able to poop at all. The reason for this varies. Crespin suggests that, sometimes, a decreased blood supply can cause your body to “internally clamp down.”

Some people just have more robust motility and peristalsis than others, meaning their intestinal muscles work more effectively, says Chutkan.

Your poop situation will quickly return to normal after your run finishes

The good news: Crespin reassures us that “most of the time, once a person stops running, their blood supply will return to normal within that same day. The human body is pretty resilient and rebounds pretty fast.”


There’s no surefire strategy to avoid pooping on your next run. But there are ways to lower your risk of any accidents. The main tips revolve around:

  • keeping your digestive processes regular
  • taking in less/no fiber just before race day
  • not switching up what you’re putting in your bod on the day
  • doing what you can to poop ahead of the race

Here are the deets.

Drink more water ahead of the run

Chutkan recommends drinking an extra eight cups of water a day (on top of your normal intake) to promote regularity in the ol’ bowels. This might make it easier to poop in the morning before your run.

Drink a warm liquid on the morning of the race

Looking for a pre-race/run evacuation? You can promote gastric motility by drinking a warm liquid, Clark says. Consuming coffee, tea, warm water, or even warm oatmeal (and giving yourself some time to digest it) can prompt a natural urge to go for a No. 2.

So wake up early on the day and see if you can’t convince your GI tract to empty itself. The less poop there is inside you, the less poop can make an unwarranted, unpleasant cameo at the 10-mile marker.

Try taking a fiber supplement — and then stop a few days before running

Taking a daily fiber supplement *up until a few days before a long run* might help regulate your bowel movements.

A 2017 study found that ground psyllium husk (Metamucil) and beta-glucan can be effective for diarrhea and constipation. Taking these alongside a high fiber diet 2 weeks before a race or long run may also help keep your pooping activities regular. A high fiber diet can promote regular bowel movements.

But wait — aren’t you looking to reduce your bowels’ enthusiasm? Well, yes, but keeping your bowels regular while your bod isn’t running might reduce the risk of unwarranted poop action on the track or trail.

Just limit your fiber intake, or cut out fiber entirely, a few days before a long run or race. This will help slow the flow.

Don’t surprise your bod with supplements or energy gels you haven’t tried

Perhaps the biggest recipe for disaster is changing up your routine on the day of a race, Clark says. If you want to try a new energy gel or supplement, experiment first during a training run to see how your body responds.

This can help you eliminate as many nasty surprises as possible before your run. For example, too much caffeine *might* make you more likely to poop – but can also be a good source of energy during an intense run. So work out in your trial courses just how it interacts with your own body, and avoid what makes you poopy on race day.

Eat foods you know your body can handle

On race day, eat foods you know your body responds to positively.

It’s best to steer clear of any foods made with white flour (like bagels, rice, and pasta), which can leave you clogged up, as well as fatty, greasy meals that are hard to digest (like, ya know, Krispy Kremes?).

OK, so we’ve heard from the folks who run sh*t on the medical side. But what about actual runners?

It may not exactly be scientific, but running blogger Eric Rayvid wakes up 2 hours before a long run or race, quickly eats breakfast, and drinks a total of 60 ounces of strong tea. This helps him get quality time in the bathroom before heading out the door.

“Because I’m up so early, there’s the added benefit of getting to races super early and not stressing about getting into my corral or dropping something at bag drop on time,” Rayvid says.

Anne Mauney, RD, a healthy living blogger and avid runner, swears by her morning cup of coffee before an endurance event. “Just make sure you drink it early enough that you have time to visit the facilities and take care of business before the race starts,” she says.

And Anthony Burdi, a well-seasoned marathoner and co-leader of The Rise NYC, recommends getting on a “morning pooping schedule.” Yes, really. “Do it first thing when you wake up, every day,” Burdi says. “On race day, you’ll be ready to let loose on the toilet well before you toe the starting line.”

But still, be prepared

Because accidents do happen, running blogger Alison Feller (who has a self-proclaimed “finicky stomach”) carefully plans running routes lined with gyms, gas stations, and coffee shops that will usually let a desperate runner in to use the facilities.

And if no bathrooms are available? “I throw a wad of toilet paper in my shorts pocket in case there’s an emergency,” Feller admits.

Running and pooping go hand in hand. Heavy exercise causes all kinds of changes in your circulation and GI tract that make your poop move faster through your body. Even just being nervous about pooping might increase your risk.

There’s no proven way to prevent pavement-pounding poopies. Keeping your diet regular but cutting out fiber a few days beforehand can help, as can drinking more water or warm drinks on the morning of your run to help you poop beforehand.

But being prepared with toilet paper is a good idea in case you *really* can’t hold back the tide and a nearby bush has it coming.

Oh, and one more piece of advice: As Jonathan Levitt, a marathoner and member of the fitness community November Project, so eloquently puts it, “Never trust a fart.” Never was there a truer word spoken.