Q: My 13-year-old son wants to start running and lifting weights. Can you give me some exercise guidelines? I'm worried about injury during this time when he is growing so rapidly.
A: First of all, congratulations on having a son who is interested in fitness and health. I will summarize exercise guidelines for your son, but first let's review the problem of youth fitness in the United States. We could benefit from more teenagers like your son.
There is a fitness crisis among U.S. children and youth. National studies indicate the following about youth fitness:
* Increasingly overweight: The proportion of adolescents who are overweight has tripled from 5% in 1980 to 15% in 2000 (1). This is disturbing because a high proportion of overweight youth end up obese as adults. Approximately half of obese school-aged children become obese adults, and more than 80% of obese adolescents remain obese into adulthood.
* Only 28% of teenagers attend physical education daily: Children and youth need daily physical education (PE) to keep fit and healthy and to help them gain the knowledge, attitudes, and skills they need to engage in lifelong physical activity (2). Schools are failing to meet this need (Figure). According to a recent report from the U.S. Centers for Disease Control and Prevention (CDC), only 56% of high school students are enrolled in a PE class, 28% attend PE classes daily, and 39% are physically active more than 20 minutes during PE classes (3). These proportions have declined since 1991 and are lower among female students and students in higher grades. Children and teenagers spend an average of approximately 4 hours a day doing sedentary activities such as watching television, playing video games, or using a computer.
* Poor upper body strength: Upper body strength is poor in many children and youth. For example, for girls aged 9 to 17, approximately half cannot perform more than one pull-up. For boys aged 6 to 12, 40% cannot do more than one pull-up, whereas 25% cannot do any. Most teenaged boys and girls do not engage regularly in strengthening exercise such as weight lifting or calisthenics.
* Poor aerobic fitness: Heart and lung fitness is lower than recommended for many young people. One third of U.S. adolescents do not engage in the minimum recommended level of moderate or vigorous physical activity (3). Approximately half of girls aged 6 to 17 and 60% of boys aged 6 to 12 cannot run a mile in less than 10 minutes.
* Many have disease risk factors: Approximately 13% of children and youth aged 12 to 17 smoke, with the proportion rising to 35% among high school seniors. Close to one in three children and adolescents have serum cholesterol levels that exceed 170 mg/dl, the level deemed "acceptable" by the National Cholesterol Education Program. A national survey by the CDC revealed that 63% of adolescents have two or more of five major risk factors for chronic disease (4). Risk factors tend to cluster and show tracking from childhood and adolescence to adulthood, meaning that every attempt should be made to bring risk factors under control while people are young.
Fitness experts from the CDC, and the Department of Health and Human Services urge that schools, communities, families, and the media work together to promote physical activity and sports for children and teenagers (5). Here are some of the central recommendations:
* Provide all children, from pre-kindergarten to grade 12, daily physical education from certified physical education specialists.
* Support more after-school programs that provide sports and active, physical play.
* Promote access to community sports and recreation programs for all young people.
* Enable communities to develop safe, well-maintained bicycle paths, park trails, sidewalks and crosswalks, and recreation facilities.
* Implement an ongoing media campaign to promote physical education and physical activity as an important part of a quality education and long-term health.
How much exercise do teenagers need? Should teenagers follow the same activity guidelines recommended for adults? Here are physical activity guidelines given by a panel of international fitness experts (6):
* All adolescents should be physically active nearly every day for an hour or longer. The activity can be a part of play, games, sports, work, transportation, recreation, physical education classes, or planned exercise with the family or community. Adolescents should engage in a variety of physical activities, and these should be enjoyable and involve most of the major muscle groups. The experts agreed that this would help reduce the risk of obesity and promote healthy bones. Unfortunately, during adolescence, time spent by both girls and boys in physical activity declines, continuing into adulthood.
* Teenagers should pursue vigorous exercise for a minimum of 20 minutes at a time, at least three times per week. Examples of recommended activities include jogging, stair climbing, basketball, racquet sports, soccer, dance, swimming laps, skating, cross-country skiing, and cycling. The consensus is that vigorous exercise enhances mental health, increases HDL-cholesterol, and increases heart and lung aerobic power.
* Weight training is recommended as a part of a comprehensive fitness program for teenagers. For many years, weight training was not recommended for children and adolescents because it was thought to interfere with bone growth and promote bone and joint injury. We now know that weight training is both safe and effective for children and youth. Still, the American Academy of Pediatrics has cautioned that children and adolescents should avoid intensive weight lifting, power lifting, and body building until they are approximately 15 years old. Moderate weight lifting by children should be under adult supervision to decrease the risk of injury. Weight training is recommended two or three times per week for 20 to 30 minutes per session and should be part of an overall comprehensive program designed to increase total fitness.
I believe that youth fitness (i.e., the lack of) is currently a national crisis. Schools, communities, families, and the media must work together now to promote physical activity and sports for children and teenagers. If we don't, much of the recent gains in life expectancy and disease prevention will be reversed as our overweight, unfit youth mature into diseased adults.
1. Ogedn, C.L., K.M. Flegal, M.D. Carroll, and C.L. Johnson. Prevalence and trends in overweight among US children and adoles cents, 1999-2000. Journal of the American Medical Association
2. Trudeau, F., and R.J. Shephard. Contribution of school programs to physical activity levels and attitudes in children and adults. Sports Medicine
3. Centers for Disease Control and Prevention (CDC). Participation in high school physical education-United States, 1991-2003. Morbidity and Mortality Weekly Report
4. Centers for Disease Control and Prevention (CDC). Youth Risk Behavior Surveillance-United States, 2003. In: Surveillance Summaries, May 21, 2004. Morbidity and Mortality Weekly Report
53 (No. SS-2), 2004.
5. Centers for Disease Control and Prevention (CDC). Guidelines for school and community programs to promote lifelong physical activity among young people. Morbidity and Mortality Weekly Report
46 (No. RR-6), 1997.
6. Sallis, J.F., and K. Patrick. Physical activity guidelines for adolescents: Consensus statement. Pediatric Exercise Science