Although children can begin weight training earlier, they don't usually build muscle until they hit puberty and hormones make it possible to increase muscle mass.
"Research suggests strength training has a lot to offer some teenagers in terms of health, fitness and fun," says Barbara Brehm-Curtis, Ed.D., a professor of exercise and sport studies at Smith College in Northampton, Mass.
Teens who work out with weights, as well as exercise aerobically, reduce by half their risk for sports injuries. Weight training also helps improve sports performance. It boosts bone density and strengthens tendons, Dr. Brehm-Curtis says.
If your teen is interested in a weight-training program, keep the following guidelines in mind.
Weight training vs. bodybuilding
Weight training is different from weight lifting, bodybuilding and power lifting. Weight training focuses on improving musculoskeletal strength and total fitness, Dr. Brehm-Curtis says. Weight lifting, bodybuilding and power lifting are competitive sports involving high-intensity training and are not recommended for adolescents.
Fitness, not superhero
Teens should train for the right reasons. Middle- and high-school students should train to increase their strength and improve their physical fitness, body composition and sports performance while reducing their injury risk. They should not aim to "bulk up" by trying to lift heavy weights.
A good teen weight-training program focuses on toning muscles with lighter weights and a high number of repetitions. Bulking up is only appropriate for young adults who have passed through puberty.
Parents should be alert if their teens are using weights to achieve a "superhero's body," says Dr. Brehm-Curtis. "This can indicate an obsession with how they look and may lead them to take steroids, which can do serious damage."
Before a teen embarks on a weight-training program, he or she should get a physical exam. Once the doctor has given the OK to begin, find a weight-training instructor who understands the special needs of adolescents. Because the skeleton isn't mature until the early 20s, too much weight can stress the joints and ligaments and may separate growth plates or damage joints in other ways.
Adult weight-training programs should not be used for teens, because these can be too strenuous and repetitious. Training typically should include using weights for 30-second intervals, followed by breaks. The teen should warm up with calisthenics and stretching before weight training and cool down with stretching afterward, Dr. Brehm-Curtis says.
Teens should be supervised at all times while strength training, and should always use safe equipment.
"Weight equipment can be heavy and dangerous, and injuries are common in home gyms," Dr. Brehm-Curtis says.
A teen should never feel pain in the joints when weight training, says Dr. Brehm-Curtis. If he or she does, it's a sign that too much weight is being lifted or too many repetitions are being done.
Training programs should begin slowly and increase gradually. Resistance shouldn't be increased too soon or by too much. A beginner should start with body weight exercises such as push-ups and sit-ups. A more advanced student can use free weights and weight machines.
The best programs emphasize proper technique, work different muscle groups on different days and restrict the youth to no more than two sets of 8 to 12 repetitions of each exercise. Two to three sessions a week on alternating days should be enough to strengthen and tone muscles.
The equipment used should be appropriate for the teen. "Smaller youths may not fit into weight machines built for adults, and injury could result because their bodies may not be properly supported," says Dr. Brehm-Curtis. "Programs for teens often rely on free weights, such as dumbbells and barbells; rubber tubing; and calisthenics, such as abdominal curls."
Focus on the individual
Training programs should be individually designed for each adolescent. Early lessons should focus primarily on safety and technique, using easily managed resistance.
Make it fun
Training should be noncompetitive and fun. Injuries are more likely to occur when youths compete to see who can lift the most and when they lift inappropriately heavy loads, which can strain developing bones and muscles.
"Weight training programs are safer when students track their own progress rather than compare themselves to others," Dr. Brehm-Curtis says.
Conditioning exercises should be part of an active lifestyle that includes plenty of other physical activity. Teens should feel comfortable with the weight-training program and look forward to it.
"Strength training isn't a substitute for games, school sports or outdoor recreation, such as riding a bike or swimming," says Dr. Brehm-Curtis. "Participating in a wide variety of physical activities helps teens stay balanced, trim and physically healthy."