Athletes who train the most, especially with high intensity, are more likely to have heavy calcium buildup in their heart arteries, which is a sign of advanced artery disease.

Men who train a lot for years—especially long hours at high intensity—tend to have more plaque in their heart arteries, even if they’re otherwise healthy.

Watches and fitness trackers that measure training intensity and duration are better at linking exercise to heart plaque than asking athletes to remember how much they trained.

Even after accounting for things like cholesterol and blood pressure, the more hours someone spends training over the year, the more likely they are to have plaque in their heart arteries.

Just doing short, intense workouts isn’t linked to more heart plaque—what matters more is how many total hours you spend training over time.

Men who train extremely hard for endurance sports like marathons or triathlons for many years tend to have more calcium buildup in their heart arteries than men who exercise moderately, even though they’re otherwise healthy.