Can one exercise too much? What is the right amount? Could stretching be counterproductive? Or even harmful? Do cortisone shots inhibit healing? Could something as simple as standing more often actually improve our health dramatically? New York Times health and fitness columnist, Gretchen Reynolds, discusses the latest research in exercise science as found in her book, The First Twenty Minutes, science that overturns many long-standing beliefs about exercise, health, athletic performance and longevity.