Every so often, after a marathon, headlines will pop up about a marathon runner collapsing and dying during or shortly after the race. It’s rare, but it happens: A 2025 study found records of 176 cardiac arrests during long-distance running events in the U.S. out of about 29 million people who finished the races.
Deaths like these raise the question of whether such an intense physical feat as a marathon can possibly be dangerous, or at least unhealthy, for the heart. We asked scientists who study marathoners about long-distance races and heart health, plus what runners can do to keep themselves safe.
Experts are pretty unequivocal: Yes. “Exercise is good for the heart,” says David Oxborough, professor of echocardiography and cardiovascular physiology at Liverpool John Moores University in the U.K. “We know that regular moderate-intensity exercise improves your cardiovascular risk, it reduces mortality, and it has real positive benefits.”
Of course, training for a marathon—which can take months or years of steady increases in endurance—is different from the act of running the race itself, says Daniel Muniz, senior lecturer in exercise physiology at the University of Hertfordshire in the U.K. “Running a marathon is a big physiological stress. You're going to hurt after…and if you look at markers in your physiology, everything is going to be all over the place.” Markers of muscle damage and heart damage are elevated, at least for a little while. (Oxborough, who has studied some of these elevated markers, says that they come back down swiftly and don’t seem to be linked to long-term damage.)
But the consistent training that running a marathon requires carries positive effects for physical and mental health, Muniz continues. “The benefits far outweigh the negatives. I think that's very fair to say.”
Dying during a marathon is extremely uncommon, says Oxborough. What’s more, it doesn’t seem random. People who die during endurance running events tend to fall into two categories, often identified after the fact: either younger people who have undiagnosed genetic heart problems, or middle-aged men who have heart disease without any symptoms.
“If you've got underlying disease, then there is a risk of sudden cardiac death. If you're under the age of 35, that is usually caused by an inherited cardiac disease, such as cardiomyopathy. As you go over 35, the main cause is more acquired disease, like coronary artery disease,” he says.
“You should, absolutely,” says Oxborough. “We do pre-participation cardiac screening for young people in competitive sport. We have charities in the U.K. It's now becoming much more accepted in the U.S., and it wasn't before. This is a simple 12-lead ECG and a questionnaire to young people.”
That’s enough to start the process of figuring out whether people might have an inherited disease, the experts say. If they do, it doesn’t mean they have to stop training. It just might shape how they decide to train and manage their risk.
The problem with coronary artery disease is that many people have no symptoms in the early stages.
If you’re thinking of running a marathon and you’re over 35 or 40, here’s what Oxborough recommends: “Go speak to your GP. Have a 12-lead ECG done. Have your blood done. Make sure your cholesterol levels are normal. Have your blood pressure taken, and if any of them show any sign that they may be a higher risk, then we recommend an exercise stress test. And if you're very lucky, if you're able to access it, a CT coronary angiogram,” he says. These are tests that will help establish your baseline and what is likely to be happening in your arteries before you really ramp up training.
Not all of these are required, but “a baseline test of risk is really important, and that you can do at your GP,” he says.
In principle, yes. “I am of the opinion that most people with training should be able to run a marathon. The important bit there is: with appropriate training for a number of months or or perhaps a year,” says Muniz.
This is not a physical challenge where you can go out and achieve it tomorrow without practice. “But if you start training and you start running for 20 minutes, or run and walk, and then transition to run for 20 minutes, 30 minutes, 40 minutes, and then you do that for a number of months, I think most people should be able to eventually run a marathon,” he says.
