Can Ultras and Endurance Sports Harm Your Health?

David Nieman, a professor of exercise physiology and immunology at Appalachian State University in Boone, North Carolina, used to be an ultrarunner. But he quit. The research—his research—was too compelling.


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In 2001, at the behest of race organizers, Nieman studied the immune responses of runners at the Western States Endurance Run, a hellishly hard 100-mile race through California’s Sierra Nevada Mountains. He recruited 45 people willing to give blood and saliva samples prerace, at mile 56, and five to 10 minutes after the race ended. He was looking for signs of inflammation, oxidative stress, and immune function—which would give him an idea of just how much duress their bodies were under. He was shocked by what he found.

“The trauma is pretty severe,” Nieman says. He found increases in markers of inflammation of up to 250 percent, plus immune system suppression. “Your immune system goes into a red-flag mode as it responds to what the body has gone through,” he says.

Then came research from Norway, published in Cancer Causes and Control. Researchers found that longtime endurance athletes had a twofold risk of developing pancreatic cancer.

Still, few ultraendurance athletes are talking about this. We spoke with several pro ultrarunners, and none were familiar with the research, including a 2018 study published in Intensive Care Medicine, which found that mountain ultramarathon finishers exhibited immune system changes similar to those of severe trauma patients. Yes, the athletes bounced back faster than ICU patients, but the idea is that athletes may be putting their bodies through significant trauma, sometimes multiple times a year.

THE TRAUMA IS PRETTY SEVERE. YOUR IMMUNE SYSTEM GOES INTO RED-FLAG MODE AS IT RESPONDS TO WHAT THE BODY HAS GONE THROUGH.

“The runners are temporarily presenting features of very severe immunosuppression,” says study author Guillaume Monneret, an expert in clinical immunology at Lyon University Hospital in France. Six days later, their levels had returned to normal. But that was after just one ultra. “For runners who are doing a lot of these kinds of races, you can imagine that they have a kind of cumulative effect,” he says.

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