A marathon pushes the human body close to its limits. Legs tire, lungs burn and the heart works hard for hours on end. For years, that strain has raised an uncomfortable question: does running 26 miles actually damage the heart?

The strongest reassurance comes from a new ten-year study of 152 recreational marathon runners, published in the journal Jama Cardiology. Researchers checked the runners’ hearts before and after races, then tracked their heart health over the next decade.

They found that although the heart’s right ventricle – the chamber that pumps blood to the lungs – showed a short-term drop in pumping ability straight after races, it recovered within days. Crucially, over the ten-year follow-up period, there was no sign of lasting damage to heart function in these runners.

This finding is important because earlier studies had raised worries that long-distance exercise might damage the heart. Much of that concern came from blood tests taken after endurance events.

After a marathon, many runners show higher levels of a substance called troponin in their blood. Troponin is released when heart muscle cells are put under strain.

Doctors normally use troponin levels to help diagnose a heart attack. So seeing these levels rise after a race can look worrying and sometimes make it harder to tell whether someone is having a genuine medical........

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