LAS VEGAS – In the opinion of Dr. Sally S. Harris, there are at least three myths associated with strength training by children and adolescents. One is that the practice is dangerous to the immature skeleton.
In fact, strength training is no riskier for injuries than are contact sports, such as soccer, football, and basketball, Dr. Harris said at a pediatric update sponsored by the American Academy of Pediatrics California District 9.
“There’s a theoretical concern than heavy weights are going to injure open growth plates,” she said. “That’s why one of the main restrictions is that kids do sets of multiple repetitions of weights 10-12 times as opposed to maximal lifts – something that you can lift only once. Proper equipment, supervision, and design are important to prevent injury.”
Dr. Sally Harris
A second myth is that strength training “will somehow bulk you up and you’ll lose flexibility, which is primarily a concern of coaches,” said Dr. Harris, who practices in the departments of sports medicine and pediatrics at Palo Alto (Calif.) Medical Foundation. “This is not true; flexibility is actually improved if you incorporate stretching with a strength-training program.”
A third myth is that no improvement in strength can occur until adolescence. This is false, Dr. Harris said, referring to published studies demonstrating that strength gains of 30%-50% can occur in preadolescence. “Prepubescent children make the same relative strength gains as teenagers and adults do, it’s just that the absolute strength gains are less, because they’re starting with less muscle,” she explained.
General guidelines for weight training prior to skeletal maturity include no one-repetition maximal lifts because of the theoretical risk of overloading growth plates, and no ballistic maneuvers or Olympic-style lifts. “These are the jerky, bouncy things like dead lifts – competitive weight-training maneuvers,” she said. “It’s not recommended that children do competitive strength training although there are young body builders, and there don’t seem to be any medical issues with that.”
Dr. Harris, who founded the AAP section on sports medicine, listed several potential benefits of strength training, including improved self-esteem, cardiovascular fitness, increased bone density, improved lipid profiles, increased lean body mass, possible improved sports performance, and possible injury prevention. However, whether strength training directly translates to improved sports performance is a matter of debate.
“There’s no compelling evidence that’s shown that general sports performance is enhanced, but we do know that if you strengthen the quadriceps, for example, you’ll improve your vertical jump,” Dr. Harris said. “You would think that might correlate to sports that involve jumping, but it’s hard to demonstrate that it enhances sports performance itself.”
According the guidelines from the AAP (Pediatrics 2008;121:835-40), proper strength training involves six to eight exercises, including core musculature and all major muscle groups, done in sets of multiple repetitions, increasing resistance in increments of 5%-10%. The recommended frequency is two to three times per week for 20- to 30-minute sessions over a course of 8 weeks, with 10-minute warm-up and cool-down periods.
Common sense guidelines include the use of proper techniques such as a straight back and slightly flexed extremities, and a spotter for heavy lifts or free weights. “Most of the serious weight-training injuries have occurred in the home setting with kids dropping barbells on their chest using their parents’ equipment,” Dr. Harris. “That’s preventable.” She went on to note that strength-training exercises should be performed in slow, controlled motions in shoes with good traction. Participants should avoid hyperventilation, Valsalva maneuvers, and the use of anabolic steroids or hormone precursors.
Dr. Harris said that parents often ask her if it’s safe for their adolescent to use creatine, a source of protein energy containing glycine, arginine, and methionine. Theoretically, the more creatine available for immediate use in muscles, the more peak power produced, “so there’s potential benefit for short bursts of exercise lasting 30 seconds or less,” she said. “You spare yourself a lactate-generating mechanism, and you have an increase in lean tissue, which allows you to train longer and more intensely.”
Humans produce creatine naturally via the liver and kidneys, but the idea is that if you supply your body with extra creatine, “you’re going to reap benefits that creatine has on generating adenosine triphosphate (ATP),” she said. The creatine “donates its phosphors to adenosine diphosphate (ADP) to make ATP, which is what muscles use for energy. The ATP in a muscle is used for the first 30 seconds of energy, so it’s beneficial for things that last less than 30 seconds like a sprint, a power lift, or a tackle. It’s not helpful for endurance activities.”