Encourage your son to eat a variety of healthy foods for growth, physical development, and his level of physical activity. Growth and physical development in teenagers who are training and competing in vigorous physical activities, especially activities that emphasize low body weight (for example, distance running, gymnastics, and ballet), may be compromised if their caloric expenditure exceeds their food intake.

Yes. In fact, there are benefits associated with being physically active during the menstrual period (for example, less cramping and lighter menstrual flow). Girls and female adolescents who experience symptoms such as severe cramping, nausea, vomiting, headache, lightheadedness, and heavy menstrual flow tend to avoid physical activity during their period. If your daughter has any of these symptoms, which usually can be managed, take her to a health professional for evaluation.

During the growth spurt, injuries such as muscle strains, sprains, and overuse are possible. The fact that they occasionally occur does not mean that your son should avoid physical activity.

With proper training and supervision, most teenagers can safely lift weights. Teenagers should not try to lift maximal amounts of weight until they are physically mature (on average, age 16 for males and 2 years after menarche for females). (The mean age of menarche is 12 1/2 years.) In addition, teenagers should not try to lift weights beyond their capabilities, and excessive repetitions and power lifting are not recommended.

After-school sports programs are a good idea if your daughter is interested in them. She may need encouragement but should not be compelled to participate.

Encourage your teenager's school to provide after-school and weekend physical activity programs. Also, community organizations, recreation centers, and churches and other places of worship provide opportunities for teenagers to participate in physical activity. Work with community leaders to ensure that your teenager has safe places for participating in physical activity (for example, walking and biking paths, playgrounds, parks, and recreation centers). Also, your teenager can do many activities at home with soft equipment that can be used in tight spaces. Examples include modified versions of bowling, basketball, darts, and golf. Additional activities your teenager can do at home include stretching, calisthenics, aerobics, dancing, and weight or strength training.