Cardiovascular exercise like running or walking has a number of health benefits. But too much exercise may be unhealthy, especially after a heart attack.

Healthy living is marked by things like not smoking or drinking too much, eating right and exercising. If you haven't done those things by young adulthood, has the damage already been done?

One part of keeping your heart healthy is keeping your arteries healthy. One thing that may help keep your arteries healthy is staying physically fit, even when you're still a teenager.