INTRODUCTION
Physical activity has beneficial consequences on nearly every organ system. In addition to the positive effects of exercise on cardiovascular1 and musculoskeletal health,2 regular physical activity is associated with a reduced risk of colon, endometrial, and breast cancers.3–4 Women who exercise, at a moderate intensity for 3–4 h per week, have a 30%–40% reduced risk of breast cancer, compared to sedentary women.5 In addition, physical activity is associated with decreased cancer mortality6 and reduced tumor size in mice that ran long distances.