Increases in body fat in the female at puberty may serve to discourage participation in physical activities. The biological drive for physical activity wanes during adolescence at the same time that increasing independence allows teenagers to manage their own lifestyles. They are thus less influenced by parents and more by their peers, and motivation for physical activity depends more on social rather than biological or family factors. All adolescents should be physically active daily, or nearly every day, as part of play, games, sports, work, transportation, recreation, physical education, or planned exercise, in the context of family, school, and community activities. Adolescents should engage in three or more sessions per week of activities that last 20 minutes or more at a time and that require moderate to vigorous levels of exertion.
Special groups deserve particular exercise prescriptions.
For example, obese adolescents may benefit from a program of increased regular energy expenditure through physical activity. Blood pressure may be reduced in adolescents with hypertension by vigorous activity, 3-4 times per week. These unique features of adolescence provide both risk and opportunities for exercise-health promotion. The following sections will examine these influences which affect the present and future physical activity of adolescents. Recognizing and understanding these factors may prove essential in developing strategies for exercise promotion at this critical period in life.