No one is immune. For people from champion athletes to desk-bound white-collar professionals, many simple acts of life--a relaxing evening stroll through the neighborhood, an exhilarating run along a sandy beach, just bending down to tie a loose shoelace-are often acts of torture. The walking wounded suffer from torn rotator cuffs, tennis elbow, jogger's knees, bad backs, stiff necks, sore feet, and swollen ankles. It could, without exaggeration,...