Your son is thirteen, plays volleyball, and for a month has been asking to sign up at the gym because "all the older ones in the team go". You would say yes, but there is that phrase you have heard repeated forever, in the bar, from a coach, from your own mother: "weights stop you growing". So you postpone. Meanwhile he keeps jumping at the net two hundred times a week without ever having done a single squat with someone watching him.
Here is the answer straight away, because on this subject time is precious.
There is no study showing that weight training stops growth. The official positions of the scientific societies say the opposite, and have been saying it for twenty years. The criterion for starting is not chronological age, but maturity and the ability to follow instructions. And injuries do exist, but almost all of them come from where you would not expect: not from load on the growth plates, but from a barbell dropped on a foot.
Where the myth comes from
The idea arises from a correct observation, that in growing bone there is a more fragile zone, the growth plate, and from a fear never verified: that compressing it under a barbell would ruin it for ever. To this were added a handful of reports of isolated cases and retrospective questionnaires: injuries in young lifters do occur, but the 2010 review in the British Journal of Sports Medicine specifies that the majority can be classified as accidental, and that the lack of qualified instruction (poor technique and inadequate loads) explains at least part of them.
The literature has taken the opposite course. The position paper of the Canadian Society for Exercise Physiology of 2008 opens by saying that numerous position stands and reviews have already refuted the myths associated with resistance training in children and adolescents, and that with appropriate methods this work is relatively safe and improves overall health. The updated position statement of the National Strength and Conditioning Association, from 2009, notes that the conditional acceptance of strength training for young people by medical, sporting and fitness organisations is becoming universal: conditional, that is, on appropriate prescription and supervision. In 2014 the British Journal of Sports Medicine published the international consensus, which grew out of the position statement of the UK Strength and Conditioning Association and was then endorsed by the main organisations of sports medicine, exercise science and paediatrics. And in 2020 the American Academy of Pediatrics updated its 2008 document, citing among the reasons the historical decline in muscular strength indices in today's children.
When four scientific societies from three different countries, within little more than ten years, write the same thing, the weight of the evidence shifts. Whoever claims that weights stop growth should bring the study. There is none.
The real criterion is not age
The Canadian position paper is explicit: there is no minimum age for resistance training in children. What must be suited to age is the training and the instruction: warm-up, cool-down, choice of exercises, equipment of the right size, gradual progression under qualified supervision.
Translated into something you can use this evening, a boy is ready when he:
- can hold his attention for the length of a session, without being called back every two minutes;
- understands a technical instruction and repeats it the same way, "push your hips back, keep your chest up", even on the tenth repetition and even the week after;
- accepts the safety rules without arguing: you do not load more because a team-mate does, you do not test your one-rep max as a bet, you do not use a piece of equipment you have not learned.
There are twelve-year-olds who tick all three boxes and sixteen-year-olds who tick none. This is the discriminant, not the birthday.
Growth plates: what the data really say
Overuse injuries to growth plates do exist, and they are a problem specific to the developing age. But where they come from is different from what most parents imagine.
A systematic review of 2017 in Sports Health gathered 24 studies on overuse physeal injuries in young athletes. The risk factors identified are periods of accelerated growth, age, body size, training volume and previous injuries. The conclusion is that these are multifactorial problems, that muscle imbalances after phases of rapid growth predispose to overload, and that the modifiable factors to monitor in order to prevent them are flexibility, strength and training volume.
Read the last line carefully. Strength appears among the things to address to prevent growth plate injuries, not among the causes. And training volume, the repetitions of the sporting gesture, the sessions, the matches, is also on the list of modifiable factors: it can be counted, and therefore it can be dosed. When the injury is already there, the most effective treatment according to that review is a prolonged period of active rest, with immobilisation of the joint when needed; the duration is not a figure the review fixes.
Honesty about the evidence: that review declares a level of evidence of 3 and admits that on risk factors and prevention the consensus is still weak. It is not a certainty, it is the best available.
The same overload mechanism, at the elbow of a young thrower or volleyball player, behaves like this: The elbow that hurts in the young athlete. At the knee it takes the name you know: Osgood-Schlatter.
Weight injuries: where they really come from
Here is the figure that is worth the whole article.
A 2009 study in the Journal of Strength and Conditioning Research queried the US emergency department surveillance system for the "weightlifting" code: 4,111 patients aged 8 to 30, divided into four age groups. The findings:
- accidental injuries decrease with age: more frequent in the 8-13 group than in 14-18, and more frequent in 14-18 than in 19-22 and 23-30;
- sprains and strains increase instead with each subsequent age group;
- two thirds of the injuries in the 8-13 group involved the hand and foot, and the descriptions most often included "dropped" and "crushed";
- in the 8-13 group the percentage of fractures was higher than in all the other groups.
The last point should be read for what it is, without softening it: the youngest break more bones. But they break hand and foot, from a dropped weight or a crushed finger, not growth plates under load. The authors' conclusion is clear: children have a lower risk than adults of sprains and strains linked to resistance training, and most injuries in young people are accidental and potentially preventable with more supervision and stricter safety rules.
The 2010 review in the British Journal of Sports Medicine points in the same direction: injuries in young lifters exist, but the majority can be classified as accidental, and the lack of qualified instruction (that is, poor technique and inadequate loads) explains at least part of them. This work can be safe and effective provided that qualified professionals supervise every session.
A third study, in the American Journal of Sports Medicine in 2010, analysed visits to US emergency departments for weight-related injuries from 1990 to 2007. Be careful: it is a series of all ages, with a mean age of 27.6 years, so largely adults: it is not a paediatric figure. It does, however, illuminate the mechanism: in 65.5% of cases the weight fell onto the person, and 90.4% involved free weights.
The message is consistent across three different studies: the danger with weights, and above all for the youngest, is a heavy object falling. It is prevented with supervision, the right equipment and rules. Not by waiting until eighteen.
What it really gains
On strength, the most solid evidence is the 2010 meta-analysis published in Pediatrics, conducted on healthy children and adolescents under 18. The overall effect size on strength was 1.12 (95% confidence interval 0.9 to 1.3), significantly greater than zero. Subgroup analyses show that maturity is a significant moderator: the ability to gain strength grows with age and maturation, but, a detail that surprises many, without an obvious jump during puberty. So there is no magic age to wait for.
In young athletes, the 2016 meta-analysis in the British Journal of Sports Medicine included 43 studies on boys and girls aged 6 to 18, all with an active control group: moderate effects on strength and vertical jump, small effects on sprint, agility and sport-specific performance.
Two honest qualifications. The gains in the youngest are largely neural: the Canadian position paper notes that the increase in strength is disproportionately greater than the increase in muscle size. The boy becomes stronger before he becomes bigger, and that is normal. And the 2016 meta-analysis concerns young athletes: transferring it to a sedentary twelve-year-old starting from scratch is a leap the data do not authorise.
The broadest perspective comes from the National Strength and Conditioning Association position statement on long-term athletic development, of 2016: today's boys' bodies are often unprepared to tolerate the loads of the sport they practise, and those who are less prepared are more exposed to overuse injuries precisely because of high competition volumes without a basic foundation. The Italian paradox is here: we worry about the 15-kilo barbell and not about the two hundred jumps at the net.
How to start and how to progress
The Canadian position paper gives a concrete outline: resistance exercise at low to moderate intensity, 2-3 times a week on non-consecutive days, with 1-2 sets at the start, progressing to 4 sets of 8-15 repetitions across 8-12 exercises, always with warm-up and cool-down.
How this translates into the first weeks:
- The first month is not for becoming strong, it is for learning the movements. Bodyweight, a stick, ridiculously light loads. It is time invested, not wasted.
- The right load is the one that allows all the repetitions with exactly the same technique, from the first to the last. If the last is different from the first, the load was too heavy.
- You go up in weight only when the technique holds, never because a week has gone by.
- The session counts within the total load, together with team training and matches. Adding two weight sessions to a boy who already trains five times a week is not adding strength, it is adding volume.
A note on intensity, because the 2016 meta-analysis is often cited wrongly: it calculated that to maximise strength in young athletes the best parameters were over 23 weeks, 5 sets per exercise, 6-8 repetitions, an intensity of 80-89% of the one-rep max and 3-4 minutes of rest. These are numbers for young athletes already trained and supervised, at the end of a path, not for anyone's first session.
The period of the growth spurt
There is a moment when caution should be raised, and it is around the peak height velocity.
A 2018 cohort study in Orthopaedic Journal of Sports Medicine followed 170 young footballers from a Dutch professional academy for one to three seasons. The average age at peak growth was 14.4 years (from 12.8 to 16.5), with 8.34 injuries per 1,000 hours of football. In the six months after the peak the incidence was 31% above the average, but with a confidence interval that touches 1.00 and a p of 0.049: a result at the edge of significance, not to be emphasised. More solid is the figure for days lost, 53% above the average. The under-15 category showed a risk 49% above the average.
The same authors add a counter-current sentence that should be reported: interventions based on the growth peak may have limited value from a screening point of view. Knowing when a boy is growing most helps to understand, it is not a test that selects who will get hurt.
The practical reading is simple. In the phase in which your child grows seven to eight centimetres in a year, movements become temporarily clumsier and tolerance to load changes from week to week. It is not the moment to increase everything together: it is the moment to keep volume under control and look after technique.
When to stop and get seen
These are the situations in which you do not wait and do not "try to see if it passes". Ask for a medical assessment if even one of these appears:
- localised pain on a precise point of bone near a joint (wrist, elbow, knee, ankle, shoulder) that lasts more than 2-3 weeks and does not go away by reducing activity;
- pain at night or at rest, that is, not dependent on what the boy is doing;
- visible swelling, deformity or inability to use the limb after a specific episode: a load that slipped, a "crack", a fall;
- back pain lasting more than 2-3 weeks in an adolescent who plays sport, especially if it worsens when arching backwards;
- tingling, loss of strength or numbness of an arm or a leg;
- dizziness, fainting, chest pain or disproportionate breathlessness during effort;
- fever, weight loss or night sweats together with bone pain.
Diffuse muscle soreness that appears two days after a new session and goes away on its own is a different matter: it is normal.
What to avoid
The one-rep max. Lifting the heaviest possible load for a single repetition is not the starting point for any boy: the recommendation of the Canadian position paper for those beginning speaks of low to moderate intensity and sets of 8-15 repetitions, not of maximal attempts.
Training with nobody watching. The 2010 review in the British Journal of Sports Medicine explains at least part of the reported injuries with the lack of qualified instruction, and it is the variable that is easiest to change: the same review considers this work safe and effective provided that qualified professionals supervise every session.
Programmes copied from social media. Designed for trained adults, they end up on bodies that are growing and already carry a load with their team. If a programme does not take into account how many times a week the boy already trains, it is not a programme.
If before even the weights you are wondering whether your son is ready for structured activity, the reasoning is the same: When a child is ready for a sport.
Getting followed
A guided path serves three things: understanding whether your son is really ready, not by age but by attention, technique and safety; setting a progression that takes into account all the load he already carries between team and matches; and recognising in time the signals that call for a pause instead of one more set.
With Ri-Hub Junior you start with a free twenty-minute introductory consultation by video call with a physiotherapist on the Italian professional register who works with children and teenagers. From 11 to 18 years the sessions are the standard ones and cost 29,90 €; up to 10 years they last 50 minutes and cost 59,90 €. It works well at a distance, because most of the work is technique, dosing and load management.
Two limits, stated before rather than after. If the signals in the list above are present, the right place is the doctor, not us. And complex neurological and neuromuscular conditions require in-person assessments and specialised centres: we do not follow them online.
In three lines
No study has ever shown that weights stop growth, and four scientific societies from three different countries have written the opposite. The criterion is not age, it is maturity: attention, the ability to follow an instruction, respect for the rules. And injuries, when they arrive, are almost always avoidable accidents: a weight falling on a foot, not a crushed growth plate. Supervision matters more than any birthday.
Sources
- Canadian Society for Exercise Physiology position paper: resistance training in children and adolescents: Applied Physiology, Nutrition, and Metabolism, 2008
- Position statement on youth resistance training: the 2014 International Consensus: British Journal of Sports Medicine, 2014
- Resistance Training for Children and Adolescents: Pediatrics, 2020
- Youth resistance training: updated position statement paper from the National Strength and Conditioning Association: Journal of Strength and Conditioning Research, 2009
- Youth versus adult "weightlifting" injuries presenting to United States emergency rooms: accidental versus nonaccidental injury mechanisms: Journal of Strength and Conditioning Research, 2009
- Resistance training among young athletes: safety, efficacy and injury prevention effects: British Journal of Sports Medicine, 2010
- Epidemiology of weight training-related injuries presenting to United States emergency departments, 1990 to 2007: The American Journal of Sports Medicine, 2010
- Effects of resistance training in children and adolescents: a meta-analysis: Pediatrics, 2010
- Effects and dose-response relationships of resistance training on physical performance in youth athletes: a systematic review and meta-analysis: British Journal of Sports Medicine, 2016
- Overuse Physeal Injuries in Youth Athletes: Sports Health, 2017
- Injury Risk and Injury Burden Are Related to Age Group and Peak Height Velocity Among Talented Male Youth Soccer Players: Orthopaedic Journal of Sports Medicine, 2018
- National Strength and Conditioning Association Position Statement on Long-Term Athletic Development: Journal of Strength and Conditioning Research, 2016
Last source check: September 2026.
