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Walking is easy, inexpensive, amazingly good for you, and has few undesirable side effects. Yet it is all too often overlooked when people consider which form of exercise is best for them.

The results surprised even JoAnn Manson, MD, MPH, DrPH, and she is supposed to know all about the subject. "No, I didn't realize just how effective walking was," says Dr. Manson, the co-director of women's health at Boston's Brigham and Women's Hospital and an associate professor of medicine at Harvard Medical School. "We always knew that walking was effective, but after looking at the results, I am surprised that walking is not readily adopted by more people."

The results came from a study presented by Dr. Manson and her colleagues at a meeting of the American Heart Association (AHA). The study, part of an eight-year research project of 84,000 female nurses ages 40-65, reported that women who walked for at least three hours a week had a 30%-40% lower risk of heart attack and stroke than women who did not walk. The study also suggested that the brisker the walk, the greater the health benefit.

"The benefits of walking are just not well appreciated," says Dr. Manson. "There is still a misperception among the public that in order to achieve any health benefit, you have to exercise vigorously or be a marathon runner. And that is just not true."