I found that you cannot judge the biological working of the body by age. People who exercise have much, much better all round function than those who sit around. So you can imagine that a 70 year old exercisers could have the same biology as a 40 or 50 year old who just sits around. A whole thirty years lost by the non exercisers.We evolved over two million years into humans. That evolution is closely linked to exercising. Humans, roamed, hunted and kept active. All our physiology is designed for high activity. As we, in modern times have become very lazy we, as a nation ,have become fat and unfit. We are not being true to our human evolutionary development. It is sad to think we are wasting two million years of evolution by considering exercise a bore instead of a central factor in our well being. We forget or neglect our evolutionary heritage at our peril.