Children and adolescents should participate in a daily minimum of 60 minutes of physical activity. Physical activity helps build and maintain healthy bones and muscles. It helps reduce the risk of developing chronic diseases, reduces feelings of depression and anxiety, and promotes psychological well being. The relationship between physical activity, health, and academic performance is well documented; physical activity can help students improve academic performance through factors such as increased concentration and attentiveness in the classroom. Excessive screen-time behaviors, such as using a computer and watching TV, for more than 2 hours daily have been linked to elevated blood pressure, elevated serum cholesterol, and being overweight or obese. Comprehensive school-based physical activity programs can help youth meet most of their physical activity needs. The CDC recommends schools provide daily physical education for students in kindergarten through grade 12, and at least 20 minutes of recess in addition to physical education.