Can you use a gym at 13?

It depends on the gym. SATS accepts members from age 11, but until the year you turn 15 a responsible adult must be with you. At Friskis&Svettis it varies: in Norrtälje you may train alone from the year you turn 13, in Borås you need a guardian’s signature and a gym induction. 1177 says you need instruction before you train on your own.

Can strength training stop you growing?

No. According to the international consensus (Lloyd et al. 2014) there is no scientific evidence that strength training has an adverse effect on growth in height or makes you shorter as an adult. The NSCA (2009) writes that no prospective study has reported injury to the growth cartilage. The risk lies in poor technique, maximal lifts and training without supervision.

Do I need protein powder?

Rarely. The Swedish Food Agency says there is seldom any need for supplements in the form of protein powder. Anti-Doping Sweden advises against using dietary supplements other than on purely medical grounds, because supplements can contain substances classed as doping.

For players

Strength training does not stunt your growth. Sloppy technique is what causes injuries.

By Gustav, founder of Breakout · 6 min read

Strength training does not stunt your growth, and the fear that it damages the growth plates in your bones has no support. Both an international consensus statement (Lloyd et al. 2014) and the US National Strength and Conditioning Association (NSCA, 2009) say so. There is no minimum age. The injuries that do happen mostly come from loads that are too heavy, poor technique and training without supervision. Start with body weight, learn the technique before you add load, and do Knee Control (Knäkontroll) with your team twice a week.

The growth plate myth has no support

The fear is that weights will damage the growth plates, the cartilage in your bones where growth in height happens. Lloyd et al. 2014 write that “fears that resistance training would injure the growth plates of youths are not supported by scientific reports or clinical observations”. Nor is there any evidence that strength training slows growth in height or makes you shorter as an adult.

The NSCA (2009) notes that injury to the growth cartilage “has not been reported in any prospective youth resistance training research study”. Most of the injuries in the old case reports were due to improper lifting technique, maximal lifts or a lack of qualified adult supervision. The American Academy of Pediatrics (AAP) wrote in 2020 that “children of all ages with proper supervision can benefit from resistance training”.

According to Lloyd et al., injuries generally occur when young people train unsupervised, with unqualified instructors or with inappropriate loads. About 77 per cent of acute strength training injuries, in young people and adults alike, are accidents. Most are potentially avoidable with appropriate supervision, a progression that follows technique and a safe training environment.

There is no minimum age, but there is a maturity threshold

The NSCA (2009) sets no minimum age. If a child is ready for sport, which generally means from age 7 or 8, they are also ready for some form of strength training. Lloyd et al. 2014 draw the line at maturity rather than age: you should be mature enough to accept and follow instructions, and have good enough balance and body control.

The Public Health Agency of Sweden’s 2021 guidelines recommend that everyone aged 6 to 17 does activities that strengthen muscles and bones at least 3 times a week. How the growth spurt affects what you get out of training is covered in the guide on training by age.

Build up in order: body weight, technique, then load

Lloyd et al. 2014 describe a clear order. You start with body weight and learn the basic movements. Once the technique is in place, free weights such as barbells and dumbbells come in. Untrained young people typically get 30 to 40 per cent stronger from an introductory programme of 8 to 20 weeks.

Our advice: let the technique decide the load. If the movement gets worse towards the end of a set, the weight is too heavy, whatever the programme says. The steps according to Lloyd et al. look like this:

Body weight first: squats, lunges, pressing and pulling movements.
New to a multi-joint exercise such as the squat: 1–3 repetitions, with feedback after each one.
Once the technique is solid: 2–4 sets of 6–12 repetitions at no more than 80 per cent of what you can lift once (1RM).
Later on: periods of 6 repetitions or fewer at over 85 per cent – as long as the technique holds.
2–3 sessions a week, not on consecutive days.

Knee Control is the strength training your team already has

Knee Control is a warm-up programme of strength, balance and jumping exercises. Waldén et al. 2012 tested it on 4,564 girls aged 12 to 17 in 230 Swedish clubs over one season: 15 minutes twice a week, six exercises – one-legged knee squat, pelvic lift, two-legged knee squat, “the bench”, lunge, and jump and landing. The Swedish FA and the insurer Folksam funded the study.

There were 7 anterior cruciate ligament injuries (0.28 per cent) with the programme against 14 (0.67 per cent) in the control group. The injury rate was 64 per cent lower across the whole programme group, and 83 per cent lower among those who averaged at least one session a week. The figures apply to ACL injuries in girls, not to all knee injuries.

Today’s version, Knee Control+ from Linköping University (LiU), starts with about 5 minutes of running warm-up followed by six basic exercises over 10 to 15 minutes, 30 to 60 seconds and 2 sets per exercise. LiU recommends 15 minutes two to three times a week. The Swedish FA recommends starting Knee Control at age 10 to 12 and gives FIFA 11+ Kids for ages 7 to 14. In Rössler et al. 2018 at least one 11+ Kids session a week was needed for an effect, and two are recommended.

FIFA 11+ is a similar programme of about 20 minutes before every training session. In Soligard et al. 2008, with 1,892 Norwegian girls aged 13 to 17, the primary outcome – lower-limb injuries – did not fall significantly. But the overall injury risk was 32 per cent lower, 53 per cent lower for overuse injuries and 45 per cent lower for severe injuries.

Our advice: do the exercises as if they count. According to LiU’s training booklet you should get tired but manage every repetition with good technique, and the strength exercises can also be done at home or at the gym, 2–3 times a week. If your team runs no programme, ask the coach whether you can start one.

Nordic hamstring and Copenhagen: good exercises, adult evidence

The Nordic hamstring exercise trains the back of the thigh and the Copenhagen exercise the groin. The evidence for them comes from adult men. Petersen et al. 2011 found 3.8 against 13.1 acute hamstring injuries per 100 player seasons among Danish male players. Harøy et al. 2019 found a 41 per cent lower risk of groin problems among semi-professional Norwegian male players.

For young players the picture is less clear. Hasebe et al. 2020 followed 259 Japanese high school boys: the number of hamstring injuries did not fall, but the injuries were less severe. Impellizzeri et al. 2021 judged the effect of the Nordic hamstring exercise to be “inconclusive”.

Both are in Knee Control+, marked as advanced: at most twice a week in pre-season and once a week during the season. Our advice: learn the basic programme first, and do not count on the same effect as in the studies of adult men.

At the gym, the gym sets the age limit

There is no general rule that you have to be 16 to use a gym. Each chain and club sets its own limits. SATS accepts you from age 11. Between 11 and 14 you train with a responsible adult, until the year you turn 15, and if you are under 18 an adult signs the contract.

At Friskis&Svettis it varies by club. In Norrtälje you may train alone from the year you turn 13. In Borås, 13- to 15-year-olds need a guardian’s signature and a gym induction, and you have to be 16 to train alone at unstaffed hours.

Our advice: ask your gym what applies and book an introduction before you train on your own. The Swedish health service 1177 puts it plainly: a child needs to be given instruction before training alone at a gym.

If you want to keep track of how much you do, you can log gym sessions and team training in Breakout: type of session, minutes and effort from 1 to 10. You then see your weekly load. Your coach sees only the weekly total, not which sessions you did.

Common follow-up questions

Can you use a gym at 13?: It depends on the gym. SATS accepts members from age 11, but until the year you turn 15 a responsible adult must be with you. At Friskis&Svettis it varies: in Norrtälje you may train alone from the year you turn 13, in Borås you need a guardian’s signature and a gym induction. 1177 says you need instruction before you train on your own.
Can strength training stop you growing?: No. According to the international consensus (Lloyd et al. 2014) there is no scientific evidence that strength training has an adverse effect on growth in height or makes you shorter as an adult. The NSCA (2009) writes that no prospective study has reported injury to the growth cartilage. The risk lies in poor technique, maximal lifts and training without supervision.
Do I need protein powder?: Rarely. The Swedish Food Agency says there is seldom any need for supplements in the form of protein powder. Anti-Doping Sweden advises against using dietary supplements other than on purely medical grounds, because supplements can contain substances classed as doping.