Youth is not in an elixir, but in lightness of step.
There will come a day, I suggest, when science will determine those who display no stiffness in their walk, are more likely to live longer. To begin with, those able to walk, period, surely live longer than those relegated to beds and wheelchairs.
The ambulatory person lives longer than the bed-ridden.
But, it goes beyond just being able to walk. How you walk is also an indicator of long life. Or, so I theorize. The person with a light step, not hindered by stiffness, is more inclined to live longer. We say that stress kills, and perhaps we can see stress causes a damaging tightness on the mind. Perhaps, as it is with the mind, so it is with the body. A person whose body is loose, not tight, will have a tendency to a longer life.
How do we achieve a relaxed body, and lightness of step? There are probably many factors, but one is just stretching. Stretch out often, and you won't be stretched out on your death bed so soon.
(Blog rewritten a little 9/17/16)