If you want to really rile up some parents, just ask them when they think a kid is old enough to safely start strength training.
Talk to someone vehemently against putting “dumbbells” and “children” in the same sentence, and their argument against youth training likely centers around one of two things: the idea that lifting weights can damage kids’ growth plates, thereby stunting their growth, and/or that weight training can increase their kids’ risk of a bone fracture.
Sounds scary, right? But here’s the thing: Both arguments are completely unfounded. There’s no truth to either of them.
“I have no idea where these myths started, but the evidence is clear: It is absolutely safe for kids to start lifting weights early in life, provided they do so under a well-designed, supervised program,” says Gregory Myer, Ph.D., director of research and The Human Performance Laboratory for the Division of Sports Medicine at Cincinnati Children's Hospital Medical Center.
Myer and Avery Faigenbaum, Ed.D., C.S.C.S., professor of health and exercise science at the College of New Jersey, are two of the foremost researchers in the field of adolescent fitness and strength training. Both say there is almost zero downside to strength training for children, as long as they’re doing a sound program and under proper instruction. What’s more, both argue teaching our kids to squat and press early in life is one of the best things we can do for them.
Here’s our deep dive on the science of weight training for kids and adolescents.
For starters, let’s define “lifting weights”
For the record: We’re not exactly talking about a 7-year-old pressing a 200-lb barbell above her head. In essence, we’re talking about training kids like adult athletes, with the goal of simply getting stronger, preventing injuries, and facilitating performance both on and off the field.
“Strength training broadly defines the method of conditioning that makes muscles stronger,” Faigenbaum explains. “One extreme is a bodybuilder mentality, where the goal is focused on aesthetics—that’s an adult goal. We’re talking about the other end of the spectrum, which is building completely functional strength.”
So no, little Sally won’t look like a bodybuilder—but she will be stronger than the other girls on her soccer team.
Resistance training can improve a young athlete's potential by preparing him to learn complex movements, master sports tactics, and step up to the demands of training and competition, according to a 2016 study analysis published in the British Journal of Sports Medicine. Furthermore, strength training actually reduces the chances of a kid getting injured playing a sport, according to a meta-analysis in Current Sports Medicine Reports. In fact, mere sports training isn't enough for kids to make the neuromuscular gains they need to prevent injury and promote lifelong health, that same analysis found. Kids actually need additional activity.
Also: Stop imagining Billy pumping iron a la vintage Schwarzenegger. “Just as with an adult, kids work at bodyweight until they can perfect their form,” Faigenbaum says. “Once a child can perform the basic movement of a bench, squat, or lift correctly, he earns the right to progress to adding weights to it. We certainly have teens in our programs who can squat double their bodyweight, but they’ve built up to that weight over time.”
And for helicopter parents concerned about their kids handling added weight, consider this: When kids run and jump and play, they land and hit the ground with an impulse load of 2–10 times their bodyweight going through their bones and joints, Myer says. That means a healthy 10-year-old boy can be looking at some 1,000lbs on his joints—which is way more than anyone’s suggesting he squat. Without learning the proper way to jump and land—and without building a strong foundation to absorb that impact—that 10-year-old boy is at a much higher risk of injury absorbing that impact without any training under his belt. In fact, resistance training can protect against injury and help nonathletic kids develop "physical literacy" to offset their sedentary lifestyles, according to a 2017 study published in Sports Health.
So how young is too young?
Most kids are ready to start intentionally building strength by 7 or 8 years old, both experts agree. The only real concern? Whether a child is emotionally ready for training. “Kids have to be able to follow instructions to stay safe, so when they have the maturity to listen and follow instructions, they’re ready for some sort of strength program,” Faigenbaum says.
Obviously some kids aren’t quite ready at age 8, but Faigenbaum’s team does strength programs with kids as young as kindergarten. At that age, strength training looks like frog squats, bunny hops, hermit crab touches, and bear crawls across the yard or gymnasium—moves that are fun and solely intended to get kids moving in all different directions, starting to build up muscle naturally.
Another gauge: If your tyke is ready for sports, he’s certainly ready for strength training, Faigenbaum adds. If your kid is already past 8, get him or her in now. Here’s why.
Why earlier is better
“Strength training trains the muscles and the underlying neuromuscular system to enhance a child’s ability to run, jump, hop, and skip,” says Faigenbaum. “Strength matters in every sport—not just football or wrestling. Jumping, throwing, kicking—strength is a prerequisite for every movement.”
Beyond setting young athletes up for success, though, strength training has a long-term effect on a kid’s development—inactive kids become inactive teens, and then inactive adults, research also shows. And since kids today are weaker than their peers were a few decades ago, the earlier they become active, the better.
“Starting strength building in high school is 10 years too late,” Faigenbaum says. “Our interventions need to start during primary school years. It seems there is a window of opportunity early in life to develop habits and train your systems in a way that propels you into more physical success for the future.”
The musculoskeletal benefits of weight training for kids
Another concept to learn: training age. Training age is a measure of how long someone has been strength training, and it’s especially important for kids as they develop and grow.
“If you start at 10, by the time you’re 16 you can handle a much higher load than another 16-year-old who has a training age of 0 rather than 6,” Myer explains.
As with adults, the earlier you start working out, the sooner you’ll see changes. But maximizing training age is more impactful in kids because they have more adaptive processes to capitalize on, Myer says. “At 14, 15, 16 years old, you have hormonal and neuromuscular factors converging, and if you have a higher training age at this point, it’s much more advantageous for yielding higher adaptations.”
If kids can build strength pre-puberty, then they’ll have that solid foundation to explode off of when their legs and arms lengthen, center of gravity changes, and hormones settle in. “The goal is to give kids a bigger engine to power their newly bigger cars,” Myer says. Girls in particular are ripe with potential because their injury risk explodes at maturation (thanks to hormones), he adds.
Plus, while you can increase bone strength as an adult, the gains you get during childhood are much greater, Faigenbaum adds. “The data says under the age of 12 seems to be the ideal time to expose the bones of boys and girls to weight-bearing physical activity, like running, jumping, hopping, skipping, playing soccer, playing tag, for optimal health later in life.”
Neurological benefits of weight training for kids
“Our brains continue to learn and evolve and become more connected until the age of 20, but this lead-up period is where our motor control becomes hardwired,” Myer explains.
For example: As an adult, agility work seriously taxes your nervous system—but over time, you adapt, and your reflexes become faster. When you’re a kid, that happens at a much faster rate: “We can adapt and alter after 20, but those growing years of peak neuroplasticity are really when we’re primed to take in motor loads and respond and adapt at a very high rate.”
The earlier you start, the more fine-tuned your neuromuscular system will be by 20.
Psychological benefits of weight training for children
“When kids are young, they all run around together. But around 6, 7, 8 years old, some start to physically change and suddenly they’re moving differently from their peers,” Myer says. Adults know not all bodies are built for speed and agility, but when kids can’t keep up with their peers, they start turning away from the things they’re not good at. That leads them down the trajectory of exercise deficit disorder, which will eventually lead to obesity, he explains.
However, if you can get those outlier kids into strength training around this time, they not only start developing their training age but also have the crucial thrill of becoming good at something. “They may be the worst at running and playing, but in strength training they can succeed, and the psychological effects of finding success compared to their peers can go a long way,” Myer adds. In fact, a 2017 study in Translational Pediatrics found in addition to reduced injury risk and increased bone strength, resistance training helped improve self-esteem in children and adolescents.
Back to those risks
When it comes to all the factors swirling around a growing body—growth plates, muscle plasticity, fluctuating hormones—strength training doesn’t affect any growth or development, both experts agree.
Of course, there are risks associated with all types of physical activity. But research shows well-devised and supervised strength training programs actually cause fewer injuries than general sports, Faigenbaum says. What’s more, the most common injuries happen to kids’ hands and feet, says a study in the Journal of Strength and Conditioning Research—the products of, say, dropping weights or catching fingers on dumbbells. “In a well-designed program, training two to three days per week, focusing on form and progression, injuries are minimal,” Fagenbam reassures.
The one peripheral factor worth mentioning: Endless studies show anabolic steroids are particularly harmful for adolescents because they freeze the growth plates in bones, stunting height. It’s reasonable to think that starting a kid down the path of weight lifting early might drive him toward anabolic steroid use early on.
But, as Myer points out, anabolic steroid use is not about the activity (weight lifting) but instead about the environment. “If a kid is going to a bodybuilding gym, maybe they’ll be exposed to steroids as acceptable, but that’s clearly not a good environment for them to be in,” he adds.
By exposing kids to strength training via gym class, YMCA programs, or organized sports, parents can steer them away from the dark side of muscle building.
Ready to get your kid lifting?
If your child is ready to start strength training, look for an after-school, technique-based YMCA program, or ask a local PE teacher—they know about the sport and know your community, Faigenbaum suggests.
It’s especially important to get them started before sports, he adds. “You can’t go from the couch to high school cross-country team, training five days a week. I think all boys and girls should perform six weeks of conditioning before they start playing a sport.”