The Best Age For Kids To Start Strength Training Is Way Younger Than You Think, New Research Shows

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WHEN Gabrielle Lyon, DO, was 5 years old, her father would take her on 10-mile bike rides. Physical activity wasn't a question, she says—it was part of her day-to-day life from a very young age. As a result, she developed a natural curiosity around strength and muscle throughout her adolescent years. Although it wasn't until she was 17 years old that she started resistance training herself, her exposure early on was impactful enough to inspire her career as a physician—and to get her own kids into the gym at a far younger age than she was.
'When you instill that kind of physicality into the cultural dynamics of the household, it changes the trajectory for children,' says Dr. Lyon, who is a board-certified fellowship-trained physician, author of The Forever Strong Playbook, and Women's Health advisor. Teaching them about exercise, and resistance training in particular, not only helps them developmentally, but also often sets them up to be lifelong exercisers.
It's kind of like kids who grow up bilingual: It's easier to learn a language when you're young, and you're more likely to continue speaking that language for the rest of your life. In this case, the language of fitness.
Some in the new generation of young people may grow up with that advantage of witnessing workouts. Parents today—many of whom are millennials—exercise in a structured way that their parents may not have, says Eva Seligman, MD, a pediatric emergency medicine and primary care sports medicine specialist at Johns Hopkins Children's Center. 'This generation of children is seeing their parents at the gym, and so it's more common for a family to do that together,' she says, adding that there has also been an influx of strength training programs designed for kids. 'I definitely see kids in my clinic who have a strength coach or go to a weightlifting class, and it's different from when I was growing up,' Dr. Seligman says.
Tiana S. Woolridge, MD, MPH, a pediatric primary sports medicine physician at Hospital for Special Surgery, agrees that more kids—both young athletes and those who are not involved in organized sports—are training more than ever before. This can be traced back to the early 2000s, when research published in The British Journal of Sports Medicine in 2009 showed more youth participating in resistance training programs. This accelerated in the 2010s, per separate research in the same journal; and today, resistance training is widely recognized as a safe and beneficial component of youth fitness, with endorsements from major health and sports bodies worldwide, according to a 2025 report in Sports Medicine.
Dr. Woolridge cites fitness influencers and social media as partially responsible. 'There have been some interesting trends that have happened in the fitness and wellness world that have trickled down to kids,' she says, including trends like the emphasis on building muscle or eating a protein-forward diet. 'Part of the benefit of that is it does push people, even if they're not athletes, to want to work out, which has obvious physical health benefits,' she says, although of course this can have the opposite effect when taken to the extreme.
Still, there's data to suggest that not all kids are primed for fitness success. The mental, physical, and development health of children in the U.S. has 'deteriorated,' according to a 2025 investigation published in JAMA. 'I strongly believe the world is going to go in two directions,' Dr. Lyon says. 'One direction is continuing tdown the path of sedentary behavior, physical dysfunction, and chronic disease. The alternative route will be one where physical habits and strength are not something unusual but simply the standard.'
And even though the National Strength and Conditioning Association (NSCA) has been issuing position statements on the importance of youth resistance training since 1985, getting kids involved still feels a bit 'avante-garde,' Dr. Lyon says. 'There are these outdated myths, for example, that training affects bone growth and there [are] lots of injuries,' she says. The other component at play is that culturally, young girls aren't encouraged to pick up, say, kettlebells from an early age, but instead to enroll in dance classes, for example. 'There is this very early mental programming that I think changes the landscape of musculature in kids,' Dr. Lyon says. 'We have to be very conscious of that if we want to change the metabolic landscape.'
All of this begs the question: When—and how—is it safe and smart for young people to implement a strength training routine?
The Effects Strength Training Has on Young Kids
You know that one friend who did gymnastics as a kid and they're totally jacked today even though they rarely hit the gym anymore? That's likely because they primed their musculature from a young age. 'Then they go into adulthood [and] are the ones that seem to be lean and fit no matter what they do,' Dr. Lyon says.
In short, resistance training increases your musclespan, which is how long you can live with healthy skeletal muscle, and the sooner you can start that process, the better, according to Dr. Lyon. 'We know that when kids train early, they lay a foundation for stronger tendons, are less at risk for metabolic disease, and seem to have a greater growth potential,' she says. Dr. Woolridge adds that this type of exercise can improve bone health in kids.
Meet the experts: Gabrielle Lyon, DO, is a board-certified fellowship-trained physician and Women's Health advisor. Eva Seligman, MD, is a pediatric emergency medicine and primary care sports medicine specialist at Johns Hopkins Children's Center. Tiana S. Woolridge, MD, MPH, is a pediatric primary sports medicine physician at Hospital for Special Surgery.
Indeed, resistance training has been shown to increase muscular strength, power, and endurance as well as improve bone mineral density, blood lipid profiles, and insulin sensitivity in youth who are overweight, increased resistance to injury, and mental health, according to 2020 research from the American Academy of Pediatrics.
This challenges the common myth that strength training stunts growth by damaging growth plates, soft areas of cartilage near the ends of bones that are more susceptible to stress. Dr. Lyon believes this myth likely originated from a few case reports in the 1970s involving children performing maximum lifts (which they shouldn't be doing) or using improper technique. But, today, 'we actually don't have medical literature to support that,' says Dr. Woolridge, who started strength training when she was 12 years old. (Her middle school had weightlifting classes.) 'I'm six-foot-two, so hopefully that helps answer the question for people about whether or not this stunts your growth.'
To further dispel this myth, Dr. Seligman says it can be helpful to understand what, exactly, this type of exercise does to the developing body. First, neuron connections get stronger, meaning there's more muscle and neuronal signals to help the muscles to fire and do the job they're being asked to do, she explains. This process promotes brain and fine motor skill development. When you start early, you develop neural pathways that, just like with learning a language, you're not going to be able to develop as well as an adult. 'There is a window to do it, and people don't want to miss that,' Dr. Lyon says. Before puberty changes, most of the strength that's happening is through those neuron connections, Dr. Seligman says. 'A little kid isn't going to get a little bodybuilder body.'
After puberty is when muscles have the potential to get larger, thanks to hormones like testosterone and human growth hormone, according to research in Advances in Experimental Medicine and Biology. 'So, in younger people, there's no more muscle bulk pulling on the growth centers, per se,' she says, noting that overuse injuries can occur if a child is not training or fueling appropriately.
With proper training, injuries are actually much less likely than they are with other sports: An older position statement from the NSCA found that the injury rate of school-aged kids for resistance training was 0.7 percent, compared to 19 percent for football and 15 percent for basketball.
In fact, strength training actually sets kids up to prevent injury in their sports or day-to-day life. 'Kids and teens who are learning movements that are based on resistance training or strength building tend to have greater effectiveness in their performance,' Dr. Seligman says. 'We see in young girls who do dynamic warm-ups and strengthening, that may reduce the risk of an ACL tear, for example.' Those improved neuromuscular connections come into play here because it develops body control. 'They're more coordinated and so they're able to move more effectively on the field or on the court,' Dr. Woolridge adds.
The mental health perks, too, should not be glossed over: 'The emotional benefits of feeling stronger and more confident in their bodies, those are beneficial,' Dr. Woolridge says. And instilling the values of fitness early on sets kids up to keep them, which is particularly important in today's sedentary and tech-obsessed culture, Dr. Lyon points out. Studies also show that kids who resistance train are more likely to engage in spontaneous play and other physical activity, Dr. Seligman says.
The Young Woman Debate
Another training myth worth busting: the idea that working out and lifting can somehow mess with girls' hormones and their menstrual cycles. For prepubertal girls without a menstrual cycle, this is inherently a non-issue, Dr. Lyon points out.
Since many myths are born from some degree of truth, it's important to understand that overtraining and/or underfueling during or after puberty can negatively impact girls' hormones and lead to amenorrhea, or the loss of their period, which happened to Dr. Lyon herself. 'Any hard-training female who's entering puberty and beyond and overtraining, that can definitely affect your period,' she says. But Dr. Lyon emphasizes that it's not the resistance training itself that's the issue: 'There is no evidence that properly implemented strength training adversely affects menstrual cycles or hormones in girls.' Both other doctors concur.
Additionally, a 2018 meta-analysis found that resistance training is not only safe, but effective, for enhancing strength in girls as young as 8 years old. (But, like with all women's health research, science around strength training for young women is lagging behind what's available for young men.)
When It's Safe (And Smart) To Introduce Strength Training
It's difficult to pinpoint an exact age at which a child is ready for resistance training because of 'developmental differences,' the American Academy of Pediatrics stated in a clinical report published in 2020. But, the authors note that beginning bodyweight exercises as young as 5 years old can be acceptable.
It really comes down to if a child is able to follow instructions and properly execute the movements, Dr. Seligman says. 'If you want someone to do squats to work on their quad strength, they have to understand how to do that motion,' she says—a degree of understanding and comprehension that typically happens around kindergarten to early elementary school. That said, Dr. Seligman suggests talking to your child's pediatrician for personalized guidance, especially if they have any conditions such as high blood pressure.
Dr. Lyon's children, ages 4 and 5, already pick up light weights when she works out in front of them, but she emphasizes that they're not on a strict resistance training program. Parents shouldn't be discouraging natural movement that sparks curiosity, she says, but an actual 'routine' is typically appropriate to implement around ages 7 or 8.
When that time comes, Dr. Seligman recommends looking for a trainer with a certification that demonstrates their ability to safely coach children. The certified strength and conditioning specialist (CSCS) certification from the NSCA and the National Academy of Sports Medicine (NASM)'s Youth Exercise Specialist certification are two solid certs. If you're a parent with an understanding of proper form and weight training, and you're confident you can provide adequate supervision, that's probably okay, too, Dr. Seligman says, comparing it to the debate many parents have over whether to hire a swim coach versus teaching their own children the skill. 'Certainly some kids need formal swim lessons [while] some kids can do it with family or friends,' she says. 'The same applies to resistance training.'
So, what does a training routine for an 8-year-old even look like? The focus should be on bodyweight exercises at a lower intensity, Dr. Woolridge says. Volume, too, should start as low as one set of six reps, making sure the child can complete the work without getting overly fatigued or losing their form. Like with grown-ups, kids should do a five- to 10-minute dynamic warm-up. A routine like this could be done two or three times a week, Dr. Lyon says.
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As far as what types of exercise should be included, it's the basics, Dr. Woolridge says—push-ups, lunges, and squats, for example. A program should be holistic, hitting all the major muscle groups. Like for adults, plyometrics can also benefit kids, Dr. Woolridge says. So with proper guidance and oversight, they could incorporate things like jump squats to 'emphasize the neuromuscular control and try to improve coordination.' For these more complex moves, have the child do multiple sets of one rep with direct supervision before scaling up the reps, a paper in Sports Medicine suggests.
From there, they can start incrementally adding weight (with light dumbbells or resistance bands), reps, and/or sets. It's also advised that kids don't strength train on back-to-back days, instead taking a full day of rest between sessions, Dr. Seligman says.
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In secondary school, things can get slightly more intense: 'My football athletes, even around the middle school age [11 to 14], they're starting to train pretty heavily and squatting and deadlifting with the barbell,' Dr. Woolridge says. Lifting heavy and even using barbells is 'not necessarily dangerous as long as there's adequate supervision and adequate rest after training as well as adequate fueling.' (Parents can check out the guidelines published by the American Academy of Pediatrics and/or the NSCA for more information.)
A gymnastics class can also be a good place to start. Gymnastics programs can improve children's overall physical fitness, including motor skills and healthy physical development, as well as cognitive performance, according to a 2025 study in Medicine & Science in Sports & Exercise that looked at 81 kids between the ages of 7 and 10.
Some red flags to watch for—at any age—include foregoing all other activities to only strength train, restricting eating, and weight loss, Dr. Seligman says. Pain is also a no-fly zone: 'A kid shouldn't have low back pain, a kid shouldn't have shoulder pain,' Dr. Lyon says. If you have young girls who have had their first period for more than a year or two, irregular or missed periods should be flagged to their doctor.
Anxiety or depression are also warning signs not to be ignored: 'Training should be fun at this age and it should be confidence building—it shouldn't be punishing,' Dr. Lyon says.
Talk to your children about their motivations to exercise, Dr. Seligman advises. 'Is it to be healthy and strong? Is it to improve performance? Is it for appearance? Is there some other motivating factor?' It's also critical to set their expectations—remember, before puberty, kids can't gain muscle like adults can. 'My kid is almost 6, but I can imagine when he's 11 or 12 and hasn't really started those hormonal changes, maybe he wants to get stronger and is frustrated because he's not seeing those physical changes, like the biceps getting larger,' Dr. Seligman says. Encouraging kids and explaining to them how they're getting stronger and making their muscles smarter, is helpful, she adds.
Talk to them, too, about role models like rugby star Ilona Maher who promote functionality over aesthetics, Dr. Woolridge says. 'What I always talk with my patients of all ages about, but especially with my teenage and young athletes, is a higher focus on body functionality as opposed to body image,' she says. 'Focusing more on what your body can do for you as opposed to what your body looks like is a proven strategy to help avoid feelings of dysmorphia or negative feelings about your body.'
Because at the end of the day, that's what strength training for people of all ages should be about—helping us to function better day in and day out, and to get the most out of this life we've been given, whether we consider ourselves athletes or not. 'It is undeniable the role that muscle and resistance training plays in nearly everything,' Dr. Lyon says, adding that kids' strength training is 'the way of the future.'
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