Even though endurance athletes have less dangerous plaque overall, about 1 in 6 still have a major blockage in their heart arteries — meaning exercise doesn’t completely prevent heart disease.

People who train hard and regularly for endurance sports are less likely to have dangerous, unstable plaque in their heart arteries that could suddenly cause a heart attack.

The presence of increased coronary artery plaque in high-volume endurance athletes is not associated with a higher incidence of clinical cardiovascular events such as myocardial infarction or cardiac death.

Endurance athletes have more heart arteries blocked by plaque than healthy non-athletes—even when both groups are fit and have normal cholesterol—meaning their arteries are affected in more places.

Men who have trained for decades in marathons and endurance sports are more likely to have calcium deposits in their heart arteries than men who don't exercise much—even if they're otherwise healthy and have no heart disease risk factors.

Men who have trained for decades as elite endurance athletes, like cyclists or marathoners, tend to have more fatty deposits in their heart arteries than healthy men who exercise moderately—even when both groups are fit and have normal cholesterol and blood pressure.