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.

Is all that running actually good for you?

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.…