All participants will receive a progressive physical activity program. Physical activity will progress from 45 min/wk in month 1 to 300 min/wk in month 4 and remain at 300 min/wk for the duration of the 18 month study for Group 1 & 2. Physical activity will progress from 45 min/wk in month 1 to 150 min/wk in month 4 and remain at 150 min/wk for the duration of the 18 month study for Group 3.