There’s a long history of athletes pooing themselves mid-race – why, and how can you avoid it?

Soiling yourself in public sounds like a bad dream. But the Australian athlete Joanna Wietrzyk has now apologised for doing just that at the Hyrox games in Beijing on Saturday.

Wietrzyk won the fitness race but not before using communal equipment with faecal matter visibly running down her legs – and muddying Hyrox’s reputation.

Apologies aside, Wietrzyk’s unfortunate case of runner’s trots, or runner’s diarrhoea, is far more common than many people realise, throwing a new light on the ominous rows of portable toilets stationed along the course of a fun run and the knowing nods between runners as they pass them (or not).

About 60% of endurance athletes report some type of gastrointestinal symptoms during training or competition, according to Kayla Henningsen, a PhD candidate researching exercise gastroenterology and extremes physiology at Monash University. The American Medical Society for Sports Medicine estimates that the prevalence could be as high as 90%.

Severity varies considerably. “Symptoms can range from mild bloating and cramping through to nausea, diarrhoea and, in rare cases, loss of bowel control,” Henningsen says. “High-intensity events such as marathons, ultramarathons and Hyrox can create the perfect conditions for gastrointestinal distress, urgency or diarrhoea.”

Safety in numbers

Wietrzyk isn’t alone: other public mishaps published over the past three decades include the 1998 London Marathon winner, Catherina McKeirnan, who dodged cameras along the way while suffering several bouts of diarrhoea. Paula Radcliffe, the winner of the 2005 London Marathon, wasn’t so lucky; she was publicly caught relieving herself of debilitating stomach pains by the road near the finish line, blaming it on too much gluten-free pasta and grilled salmon the night before. In 2024 the US athlete Taylor Knibb won the Dubai T100 despite having to relieve herself during the race, uttering the immortal line to a camera operator: “I just shit myself … so can you not get my ass? Thank you.”

Although runner’s trots are more common in women, men aren’t immune. The TikTok celebrity Davis Clarke decided a toilet stop would impact his time so he crapped his pants during the 2024 Boston Marathon. In a 50km race walk at the 2016 Olympics, the French world record-holder Yohann Diniz suffered stomach pain and had blood and possibly diarrhoea dribbling down his leg before collapsing – then still managed to finish in eighth place.

Perhaps most cringeworthy episode afflicted a Swedish runner, Mikael Ekvall, who ran a half-marathon in 2008 withdiarrhoea running down his leg, earning him the viral nickname “bajsmannen” (poop man). He finished in 21st place despite 10km of severe stomach cramps.

An ancient ailment

The scientific literature has recorded gut problems related to exercise stress, known less colloquially as “exercise-induced gastrointestinal syndrome”, for the past century, according to Prof Ricardo Da Costa from Monash University and colleagues. They write that it’s likely to have plagued competitive athletes since the ancient Olympics.

Despite this, and the large volume of cases seen by sports professionals, they note that an understanding of why and how endurance exercise stresses the digestive tract only started to develop in the 1980s and 90s, and is still relatively unclear – possibly because it can’t be pinned to one straightforward cause.

Exercise diverts blood to skeletal muscles, affecting the motility and absorptive ability of the digestive tract. Reduced absorptive capacity can especially affect the lower intestines when athletes load up with drinks, gels and bars during exercise, according to Prof John Hawley from Australian Catholic University.

“Events in the heat make the problem worse,” he adds, “as blood that would normally go to the gut is diverted to the skin for cooling and to preserve core temperature.”

He says that prolonged weight-bearing exercise for 90 minutes or more, such as running, can produce more severe symptoms than other endurance-based exercise. “This is because of the vertical up-and-down impact, and why cyclists can tolerate a lot more food and drink.”

Henningsen refers to this as “mechanical jostling of the intestines” and adds dehydration and intolerance of certain foods or nutrition protocols to these potential causes.

Da Costa’s team refers to the gut-brain axis possibly directing performance stress to the gut – potentially through the hormonal stress response and/or the microbiome – among other factors including altered pH.

Can it be prevented?

From a sports physiology perspective, Henningsen says runner’s trots and other gut problems highlight the stress that extreme exercises places on the body: “These events are not necessarily a sign of poor preparation or poor fitness.”

While risk can be reduced, it may not be completely eliminated, she notes, suggesting prevention strategies such as avoiding unfamiliar foods before a competitive event, staying well hydrated, managing heat exposure and gradually adapting the gut to tolerate carbohydrates and fluids while exercising. But because triggers can differ between individuals, she says, a personalised approach is usually most effective.

Hawley explains that “the gut is an ‘athletic organ’ and can be trained to tolerate nutrient loading – that is, eating and drinking during exercise – so practise in training what you will be doing in a competition”.

Henningsen agrees, saying the most important advice is “to treat your gut like any other part of your performance system and train it accordingly”. She recommends keeping a record of foods, fluids, symptoms and environmental conditions to look for any patterns.

In addition to these recommendations, Da Costa and colleagues cite evidence that ingesting carbohydrates during prolonged exercise may help. They also review positive findings that proteins, especially glutamine, may support gut integrity and note possible benefits from low-fibre and gluten-free diets. But the evidence for these remains unclear.

Fortunately, according to Hawley, “most GI symptoms are mild, transient, and of no risk to long-term health”.

But Henningsen offers a caution: “If symptoms are frequent, severe or worsening, see a healthcare professional. Persistent gastrointestinal issues should not simply be accepted as ‘part of the sport’.”