too much exercise can be harmful to the heart
You don't think it has anything to do with exercising the heart muscle?
Sounds pretty bogus to me. What I know is that there are several longitudinal studies going for years to determine who lives the longest and healthiest and least obese lives. It's those who follow the so-called Mediterranean Diet, though only one community studies is actually in the Mediterranean. Few of these people exercise formally. They don't live sedentary lives, they walk or ride bikes instead of drive, eat balanced diets with low intake of red meat, the basics. But they don't go to gyms, they don't go around jogging, for the most part. I think where aerobic exercise comes in is in societies where people are sedentary, such as in the US where so many sit and watch TV or their video devices and sit at desks most of the time. But aerobic exercise also leads to injuries, more and more of them as we age, which leads to surgeries and drugs, which leads to death. Lots of ways to get sick and to die out there. I'm guessing there's a Goldilocks amount of exercise out there, not "the more" you get. Just getting enough. Too much is harmful. Too little is harmful. But again, you look at those studies, and they aren't obsessing over exercise. Wonder who paid for this study. Cigarettes kill. Lack of exercise? Really?