To avoid soreness and injury, individuals contemplating an increase in physical activity should start out slowly and gradually build up to the desired amount to give the body time to adjust. People with chronic health problems, such as heart disease, diabetes, or obesity, or who are at high risk for these problems should first consult a physician before beginning a new program of physical activity. Also, men over age 40 and women over age 50 who plan to begin a new vigorous physical activity program should consult a physician first to be sure they do not have heart disease or other health problems. Adults More than 60 percent of adults do not achieve the recommended amount of regular physical activity. Nearly half of young people aged 12-21 are not vigorously active on a regular basis.
Physical activity declines dramatically with age during adolescence.
Female adolescents are much less physically active than male adolescents. In high school, enrollment in daily physical education classes dropped from 42 percent in 1991 to 25 percent in 1995. Only 19 percent of all high school students are physically active for 20 minutes or more in physical education classes every day during the school week. This report identifies promising ways to help people include more physical activity in their daily lives. Well-designed programs in schools to increase physical activity in physical education classes have been shown to be effective.