March 1, 2019&mdash;Is extreme exercise dangerous for the heart? No, a new study suggests, despite past concerns to the contrary. It found that frequent, high-intensity exercise was safe, even for older male athletes with signs of early heart disease. 

The study looked at data from 1998 to 2013 on nearly 22,000 generally healthy men, age 40 to 80. Most were runners, but some were cyclists, swimmers, rowers and triathletes.

The calcium connection 

All the athletes reported their activity levels. They also had imaging tests to check for a buildup of calcium in the arteries that feed the heart. That buildup is a sign of atherosclerosis&mdash;a disease in which plaque clogs arteries. 

Past research raised red flags about too much exercise, because some very active athletes have higher levels of coronary calcium. 

But this new one found that a majority of the most highly active athletes still had low calcium levels. And even those with higher levels did not face a raised risk of dying from heart disease. 

Despite these reassuring findings, it's still important to slowly increase the amount and intensity of your exercise, the researchers warned. Always get an OK from your doctor before starting any vigorous exercise. 

To learn more, read the full study. It appeared in <a target="_blank" href=" https://jamanetwork.com/journals/jamacardiology/fullarticle/2722746?guestAccessKey=3c09c9c9-2972-4158-a259-62acd9f7c23c">JAMA Cardiology</a>.

Extreme exercise not likely to put your heart at risk

Worried your HIIT workout will give you a heart attack? Don't be.