Ultra races health research
As more people tackle ultras, researchers-and some athletes-worry about long-term health problems stemming from chronic inflammation.ANTOINE DORÉ

Can Ultramarathons and Endurance Sports Harm Your Health?

MIKE WARDIAN IS the picture of health. At 45, he’s been a professional ultrarunner for 16 years. He races 50-plus times annually, covering around 200 miles a week. He’s six feet tall, weighs 145 pounds, and has a body-fat percentage of 8.5. His resting heart rate is 38 beats per minute. He has 20/20 vision. And he’s never had a cavity.

Yet every four months, Wardian goes to a cardiologist for diagnostic testing. It’s not for some congenital heart disorder, either. It’s because of his sport.

In the 2008 Olympic Marathon trials held in New York City, fellow runner Ryan Shay collapsed and died; the cause was later attributed to an irregular heartbeat and an oversize heart. The incident spooked Wardian enough to closely monitor the health of his own heart. “It is one of those things where you think, yeah, this may not be that good for you,” he says.

Exercise is healthy, of course. But there can be too much of a good thing. A handful of researchers are now suggesting that participating in ultraendurance sports may be harmful to your long-term health. Cardiologists at the University of Toronto published a study that found highly trained endurance athletes are three to five times likelier to experience an atrial fibrillation, like Shay suffered. And with the entries rising for marathons, triathlons, and ever-gnarlier adventure races, more people may be unknowingly putting themselves at risk.

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Exact numbers are hard to come by, but Ultrarunning Magazine reports that in 2016, there were 1,473 ultras. In 2006, there were 369. Running a marathon was once seen as hardcore. Now it is commonplace. So people who want to prove their mettle are taking things up a notch. Ironman triathlons—a 2.4-mile swim, 112-mile bike ride, and a marathon— often sell out in minutes. And “doubling” is a thing now. Marathoners, triathletes, and even Ironman athletes compete in multiple races in one season, sometimes weeks apart. There are even people who do a “Double Boston.” They meet in the wee hours on Boston Marathon morning on Boylston Street at the finish line and run the reverse course to Hopkinton. A few hours later, they line up with the rest of the marathoners and run the course again. By day’s end, they’ll have logged 52.4 miles. And as the distance covered on race day grows, so is the time spent training.

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 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.

Monneret and Nieman can’t help but speculate that the excessive amounts of inflammation built up during weeks of training, followed by the race, may have long-term consequences. “Cancer can be a reflection of immunosuppression, and when someone is in that chronic state, certain cancers may be able to flourish,” Monneret says.

So should you be racing hundred-milers every few months or competing in back-to-back Ironmen? Nieman says no: “I think their zeal outweighs their common sense.”

But other researchers say this is alarmist. “Inflammation is a good thing—it’s what our bodies adapt to,” says Matthew Laye, a professor of health and human performance at the College of Idaho. With repeated exercise, the body starts regulating down its inflammatory response—basically, it gets used to the mileage. “All the data I know about from epidemiological studies shows that exercise is protective against cancers—especially colon and breast cancers,” Laye adds.

In fact, doctors are using exercise to help cancer patients. Researchers in Alberta, Canada, found high-intensity interval training can help recent testicular-cancer patients cope with post-chemo fatigue and can boost heart health. And a study from the Dana-Farber Cancer Institute in Boston shows that recently treated colon-cancer patients who exercised more had better prognostic biomarkers than those who moved less. Basically, their lab tests suggest cancer in the high-exercise group is less likely to come back. But they were moving 300 minutes a week. For ultra-athletes, that’s one long run.

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Ultimately, whether it’s worth the risk is a personal choice. “I love ultras and the challenge is a great experience,” Nieman says. “But I believe in our data that concludes they are more harmful than healthy.”

Laye disagrees. “I don’t think that saying it can lead to illness later in life is reasonable,” he says. Laye points to research that finds Tour de France participants are healthier, longterm, than the rest of us.

And as for Wardian, he sees it a bit like booze, where science says something different every other week. He stays apprised of research, but hasn’t come across anything that’s compelled him to back off running. “It would have to be: Doing this causes severe harm and will shorten your life span,” Wardian says. “You have to weigh the consequences. I love the sport, and I love being out there.”


If inflammation is the root of all ills, it would make sense that popping a nonsteroidal antiinflammatory drug (NSAID) like ibuprofen or naproxen would stave off damage. Athletes often take them believing they’re safe and that the drugs will help them train through the pain. But it actually seems to make things worse.

A study conducted by David Nieman found athletes who took NSAIDs at the Western States 100 endurance run had 40 percent higher inflammation levels postrace. Worse, the pills didn’t make the run easier.

Runners who had taken NSAIDs reported levels of soreness and exertion equal to those who did not. But most distressing was that runners who had tried to thwart imminent pain had small amounts of bacteria from their colon leached into their blood, most likely because the NSAIDs had increased the permeability of their intestinal lining.

That’s another knock on NSAIDs: They can injure your gastrointestinal tract. And it appears taking them before exercising (as opposed to afterward) exacerbates that, according to a small study of endurance cyclists, in the Medicine & Science in Sports & Exercise.

One other thing worries doctors. Unlike prescriptions, for which dosages are overseen by a professional—people can pop NSAIDs to excess. In a study of 764,228 U.S. Army soldiers (who exercise a lot and don’t have desk jobs), more than seven doses of NSAIDs a month was associated with an increase in chronic kidney disease diagnoses.

Conclusion? Pop them once in a while postworkout for sore muscles. Any more than that, consult a doctor.

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