In the old days, folks pretty much expected that their bodies would wear out when they turned 65. That was one reason why they retired. It was only fairly recently that medical research advanced to the point where it became clear that people around that age don’t just wear out. They fall apart when they don’t get enough physical activity. Ooops!
So the old idea that retirement meant getting more rest was, in effect, a sort of death sentence. Folks in my parent’s generation understood this and began to exercise more. By and large, they started to live longer and better.
These days, we are more aware of how the body ages and what types of physical effects of aging are countered by exercise. Here are a few, courtesy of the Mayo Clinic.