Ask the doctor: Does exercise help damaged heart muscle?

Q. After my heart attack, my doctor told me that damaged heart muscle cannot be replaced. If this is true, why am I walking on a treadmill five days a week? Is this helping repair the heart muscle damage or strengthen what's left of my heart muscle?

A. Your skeletal muscles can repair themselves after an injury — pull your calf muscle and, after a few days or so, it heals. Until recently, it was believed that the human heart didn't have this capacity. But the heart does have some ability to make new muscle and possibly repair itself. The rate of regeneration is so slow, though, that it can't fix the kind of damage caused by a heart attack. That's why the rapid healing that follows a heart attack creates scar tissue in place of working muscle tissue.