Inactivity during childhood and adolescence increases the likelihood of being inactive as an adult. Adults who are less active are at greater risk of dying of heart disease and developing diabetes, colon cancer, and high blood pressure. Half of American youths aged 12-21 are not vigorously active on a regular basis, and about 14 percent of young people report no recent physical activity. Participation in all types of physical activity declines drastically with both age and grade in school. Being physically active helps build and maintain healthy bones, muscles, and joints. It helps control and maintain weight, build lean muscle, and reduce fat. In addition, exercise helps to prevent or delay the development of high blood pressure. Moderate amounts of physical activity are recommended for people of all ages.  The U.S. Department of Health and Human Services establishes physical activity guidelines for all Americans.  Currently, it is recommended that children and adolescents do 60 minutes or more of physical activity every day and perform muscle-strengthening physical activities on at least 3 days a week.