The statement that exercise is good for you is, in the 21st century, noncontroversial. The volume and quality of data that demonstrate the positive health outcomes associated with either an active lifestyle or with systematic exercise training in either healthy individuals or those with cardiovascular disease is substantial. This concept is supported by an organizational theme used by the American College of Sports Medicine, “Exercise Is Medicine,” which suggests that the health impact of regular exercise is of the same order of magnitude as the benefits of pharmacological therapy for hypercholesterolemia, hypertension, and smoking cessation. Guidelines, whether for habitual activity or structured exercise training, have been widely accepted, and there are extensive public health recommendations regarding exercise training.

However, regardless of the benefits of exercise, ...