So many older people, they just sit around all day long and they don't get any exercise. Their muscles atrophy, and they lose their strength, their energy and vitality by inactivity.
Jack LaLanneMuscle cells strengthen in response to intense exercise - whether you're 18 or 88. But the intensity is what's lacking in most people's workouts. And there are doctors who'll give you the advice, "Well, don't push it."
Jack LaLanne