For lifelong heart health, start exercising early in life and keep exercising often — ideally, at least four times a week, according to a remarkable series of recent studies involving hundreds of people and their hearts.

But even if you have neglected to exercise in recent years and are now middle-aged, it is not too late. The same research shows that you still can substantially remodel your heart and make it more youthful by starting to work out in midlife, provided you exercise often enough.

By the time many of us are in our mid to late 50s, portions of our heart muscle have begun to atrophy and weaken, and our major cardiac arteries — the blood vessels that move blood from our hearts and to the rest of the body — have stiffened.

These changes increase blood pressure and make our hearts work harder and less well, raising the risk for subsequent health problems, including heart failure.