This snippet from a NYT article titled "What's the single best exercise?" dated 15/04/2011
“I personally think that brisk walking is far and away the single best exercise,” said Michael Joyner, M.D., a professor of anesthesiology at the Mayo Clinic in Rochester, Minn., and a leading researcher in the field of endurance exercise.
As proof, he points to the work of Hiroshi Nose, M.D., Ph.D., a professor of sports medical sciences at Shinshu University Graduate School of Medicine in Japan, who has enrolled thousands of older Japanese citizens in an innovative, five-month-long program of brisk, interval-style walking (three minutes of fast walking, followed by three minutes of slower walking, repeated 10 times). The results have been striking. “Physical fitness — maximal aerobic power and thigh muscle strength — increased by about 20 percent,” Dr. Nose wrote in an e-mail, “which is sure to make you feel about 10 years younger than before training.” The walkers’ “symptoms of lifestyle-related diseases (hypertension, hyperglycemia and obesity) decreased by about 20 percent,” he added, while their depression scores dropped by half.
Walking has also been shown by other researchers to aid materially in weight control. A 15-year study found that middle-aged women who walked for at least an hour a day maintained their weight over the decades. Those who didn’t gained weight. In addition, a recent seminal study found that when older people started a regular program of brisk walking, the volume of their hippocampus, a portion of the brain involved in memory, increased significantly.