Is marathon heart damage a myth?

December 14, 2025

For years, the long-distance running world has had this nagging question hovering over it: are we slowly wearing out our hearts? The worry didn’t come from thin air. After big endurance efforts, some runners show temporary changes on echocardiograms, and some have a spike in a blood marker called troponin—a protein released into the bloodstream when heart muscle cells are stressed or injured, and one doctors use when they’re assessing possible heart attacks.

A new long-term follow-up study, published in JAMA Cardiology, finally tested the part whether those finish-line blips turn into lasting damage years down the road.

Researchers followed 152 male recreational marathon runners (mean age 43) and measured heart function and biomarkers before the race, immediately after, at one day and three days, and again at 10 years.

Right after the marathon, right-ventricular ejection fraction dropped—the same kind of finding that has fueled concern. The median value went from 52.4 per cent pre-race to 47.6 per cent immediately after finishing. By the next day, it had improved to 50.7 per cent, and by day three it was essentially back (51.3 per cent). Ten years later, it was still stable at 51.9 per cent. The dip showed up, it resolved within days, and it didn’t drift downward across a decade. Running Magazine