AW is a 55-year-old male pharmacist. Although he is generally in good health, his long work hours prevent him from participating in any routine exercise. His brother, BW, is a 56-year-old college professor. A former high school athlete, he runs or cycles each day. The third brother, CW, is a 54-year-old businessman and the recipient of a heart transplant. Since the surgery 3 years ago, CW has strictly adhered to his cardiac rehabilitation program and exercises daily. One Saturday morning,