- PHASE II: Current physical activity level exceeding Centers for Disease Control and Prevention (CDC) guidelines for activity (60 min of moderate-vigorous exercise/day for 5+ days/week (wk) including 3+ days of vigorous intensity activities and muscle-strengthening exercises on 3+ days/wk and bone strengthening exercises on 3+ days/wk for children < 18 and 150 min of moderate vigorous exercise or 75 min of vigorous exercise/wk and 2+ days of muscle strengthening activities for adults >= 18); the CDC guidelines are used to determine exercise prescription in our intervention; individuals already exceeding the guidelines would be unlikely to benefit from participating