When it comes to appreciating the athletic capacity of the human body, few activities can equal the marathon. Runners pound pavement for 26.2 miles, taking graceful and gazelle-like strides in an attempt to conquer the physical and mental challenges of endurance.

Their movements can appear almost balletic. Until they poop in their shorts.

Some athletes call it runner’s trots. Others refer to it as the Gingerbread Man. It’s the sudden and explosive need to empty one’s bowels in the heat of a race.

Sh*t Happens

The history of marathoning is littered with these fecal footnotes. During the 1982 World Ironman Championship in Hawaii, Julie Moss soiled herself in front of 20 million viewers tuned into ABC’s Wide World of Sports. In the midst of the 2005 London Marathon, participant (and eventual winner) Paula Radcliffe was forced to repeatedly pause and let the contents of her intestines empty out in full view of the crowd and television cameras. Countless runners in practice or in regional competition have undoubtedly experienced the wrath of the Gingerbread Man.

The problem is pervasive enough that in 2017, two bystanders at the New York City Marathon brandished handmade signs. “Don’t Poop Your Pants!” read one. “Nobody Poop” read the other, held aloft by a child.

While athletes in other sports have reportedly dealt with in-game mud butt, most attribute it to food poisoning or illness. In marathoning, the continuous physical exertion is typically to blame.

“It’s related to the fact that during periods of physical stress, the body shunts blood away from organs that are not necessarily critical at that moment,” Michael Dobson, D.O., a colon and rectal surgeon with Novant Health in Charlotte, North Carolina, told Mental Floss in 2021. “For endurance athletes, you’re shunting blood away from the intestines and toward the muscles. The lack of blood flow to the intestinal system can cause a lot of disruptions to normal function. The bottom line is it causes irritation to the intestinal system. That can result in evacuation of bowel movements.”

When a runner’s leg muscles are working overtime, less blood is going to their intestines. That causes an inflammatory response in the lining of the gut, which can lead to ischemic colitis, or transient inflammation. That’s when trouble starts brewing.

“Even without a big meal, the body still secretes liters of fluid a day in the intestinal system,” Dobson said. “When there are stressors in play, it’s causing that stuff to rush through the pipes.”

The Last Line of Defense

People can suffer from intestinal issues without necessarily soiling themselves. What gives runners a poop they can’t ignore is losing control of both their interior and exterior sphincter muscles at the end of the anal canal. Given enough volume of waste, the involuntary muscle that typically keeps poop out of one’s pants relaxes. The exterior voluntary muscle is the last line of defense, but the runner can’t squeeze it.

“Someone in the middle of a strenuous physical activity, it’s really hard to voluntarily keep the muscle closed while engaging in other activities with other muscles in the legs and pelvis,” Dobson said. “You can’t control the muscle when using muscle.”

That’s when you begin to doubt what you ate last. But according to Dobson, aside from limiting your solid food intake before a race or avoiding Taco Bell, there’s not much you can do.

Given that up to 60 percent of marathoners are faced with gastrointestinal issues at some point, wouldn’t it make sense to wear some protection—like, say, an adult diaper?

“I don’t know about the benefit of that,” Dobson said. “The accident is still going to happen. Now you have something heavy and wet. A wet diaper. There’s nothing on the market that’s going to make that better as opposed to just evacuating it. It might be more disruptive, running with a heavy, wet garment. It would be restrictive.”

It would also cost them one of the rites of passage of the sport. “I remember that an ultra-marathoner once told me that it was a badge of courage,” Dobson says. “You’re not in the club until you’ve sh*t yourself in an ultra-marathon.”

A version of this story originally ran in 2021; it has been updated for 2023.

This article was originally published on www.mentalfloss.com as Why Do Marathon Runners Poop Their Pants?.