* currently exercising more than 60 minutes per week at a moderate intensity or 30 minutes per week at a high intensity * current use of supplemental oxygen * active treatment for cancer * severe congestive heart failure, pulmonary disease, stroke, peripheral vascular disease, coronary artery disease and/or valvular heart disease * positive graded exercise test * major psychiatric disease * severe liver or hepatic disease * uncontrolled hypertension or diabetes * orthopedic impairment that prevents participation in an exercise program * blindness * bmi \> 40kg/m2 * living more than 35 miles from exercise facility * plans to move within the next 6 months

* currently exercising more than 60 minutes per week at a moderate intensity or 30 minutes per week at a high intensity * current use of supplemental oxygen * active treatment for cancer * severe congestive heart failure, pulmonary disease, stroke, peripheral vascular disease, coronary artery disease and/or valvular heart disease * positive graded exercise test * major psychiatric disease * severe liver or hepatic disease * uncontrolled hypertension or diabetes * orthopedic impairment that prevents participation in an exercise program * blindness * bmi \> 40kg/m2 * living more than 35 miles from exercise facility * plans to move within the next 6 months

- currently exercising more than 60 minutes per week at a moderate intensity or 30 minutes per week at a high intensity - current use of supplemental oxygen - active treatment for cancer - severe congestive heart failure, pulmonary disease, stroke, peripheral vascular disease, coronary artery disease and/or valvular heart disease - positive graded exercise test - major psychiatric disease - severe liver or hepatic disease - uncontrolled hypertension or diabetes - orthopedic impairment that prevents participation in an exercise program - blindness - bmi > 40kg/m2 - living more than 35 miles from exercise facility - plans to move within the next 6 months

- currently exercising more than 60 minutes per week at a moderate intensity or 30 minutes per week at a high intensity - current use of supplemental oxygen - active treatment for cancer - severe congestive heart failure, pulmonary disease, stroke, peripheral vascular disease, coronary artery disease and/or valvular heart disease - positive graded exercise test - major psychiatric disease - severe liver or hepatic disease - uncontrolled hypertension or diabetes - orthopedic impairment that prevents participation in an exercise program - blindness - bmi > 40kg/m2 - living more than 35 miles from exercise facility - plans to move within the next 6 months