For children ages 6 and older and adolescents, the U.S. Department of Health and Human Services (HHS) recommends at least one hour of physical activity every day, including vigorous exercise at least three times per week. Kids should get a mix of aerobic (hiking, for example), muscle-building (rope-climbing) and bone-strengthening (running) activity. Hagan puts it simply: "Ideally I want you to be sweaty for an hour every day." That means limiting TV time to less than two hours per day and encouraging children to be active — how is up to them. Bike-riding, jumping rope, soccer, playing outside after school? "That's all really good exercise," Hagan says.