"Thirty to fifty percent of aging and illness is due to inactivity. The two major benefits of walking are that it prevents bone loss, which can lead to osteoporosis, and it strengthens muscles and joints, which helps prevent arthritis. Other conditions like diabetes and hypertension can also be avoided by walking."
Dr. Richard M. Lampman of the Department of Physical Medicine and Rehabilitation at the University of Michigan

"...regular walking is associated with a lower overall mortality rate. Encouraging elderly people to walk may benefit their health."
New England Journal of Medicine 1998; 338:1622-1623, May 28, 1998

"...both walking and vigorous exercise are associated with substantial reductions in the incidence of cardiovascular events...Prolonged sitting predicts increased cardiovascular risk."
New England Journal of Medicine 2002; 347: 716-725, September 5, 2002