Weight training for kids – best workout or a way to stunt growth?

weight training for kids

We have previously seen how unsubstantiated fears kept most women away from weights for many decades because someone, somewhere took a liberty of defining women as overly fragile, helpless beings that were unable (and unwilling) to ever lift more than the weight of their purses.  (Of course, producers of 0.5lb barbells missed the fact that just to be prepared for the challenges of everyday life, women would need to lift, push, squat and carry much higher weights – like their own babies).

In any case, hopefully, you realize by now that when we compare males and females – there are more similarities than differences in metabolic pathways, muscular function and useful methods to achieve athletic and health goals.  So this limiting belief does females a great disservice.

But a similar ill advice and unsubstantiated fears are now defining our attitudes towards weight training for kids.  Most parents still have many reservations when it comes to weight training for kids – because they have heard, at some point, that lifting weights stunts growth (and that lifting free weights causes injuries, generally speaking).

How much of it is true?  Does weight lifting stunt grown in children, as many people believe?  Are there benefits of weight training as a part of structured exercise early in life? And, if you are a parent – what should you know about your child’s training protocols?

Let’s try to take a closer look.

Stereotypes and the dangers of conventional stupidity

“Conventional wisdom” states that weight training for kids does not work well.  Rumor has it that children should not lift weights until a certain age (typically around 18 or so), otherwise it might cause irreversibly stunted growth by leading to a fusion of epiphyseal (“growth”) plates.  In the eyes of those who recommend staying away from dumbbells and barbells, kids should only perform very limited and very specific types of physical exercise.

That’s why you would be hard pressed to find a decent workout program for kids involving free weights.

But when it comes to getting results – fear is a very bad advisor.  Especially, when it is completely unsubstantiated.

After all – although some overprotective parents think that this will totally break them and try to restrict it as much as possible – kids too have to haul their heavy backpacks to school every day, lift them up from the ground and, often, above their heads when storing them.  It is not possible to get through life without performing some sort of lifting.  When they play – whether they are climbing on monkey bars or running around with a ball or engaging in any other activity that routinely requires them pulling or pushing at least half of their bodyweight (and if you factor in ground reaction forces – we can easily be talking multiples of body weight)– stronger muscles not only make these activities possible and much more enjoyable and successful, but also often prevent injuries – injuries that often lead to epiphyseal fractures in the first place.

So here are a few reasons why kids should lift weights.

First, “official” prescribed physical education in most schools is failing dismally.  There just isn’t enough of it – unless your kids are on some school sports team, exercise (at least in North America) is limited to about once a week, on average, with limited duration.  Most people see this as leading to obesity epidemic – and, to a certain degree, it does, given that there is a complete mismatch between the amount of energy kids get through food and the amount of energy they expend.  But it is a fallacy to think that you can exercise your way out of a bad diet (the failure of the US “Let’s Move!” initiative proves that).  So, as a measure of controlling child obesity – just moving doesn’t really work as well, if it is not accompanied (and often – preceded) by controlling what kids eat.  But we digress…

Second, we are not just concerned with maintaining some ideal body composition with children.  We are also concerned – often more than anything else – with establishing appropriate foundation for their future physical and mental development.  Being overly protective and restricting exercise that we often mistakenly perceive as “dangerous” doesn’t do them any good.  With kids – just as with women and the elderly, where this fallacy was allowed to propagate beyond belief – the truth about what would happen if they start lifting weights is very far from the perception that most people have.

Of course, compared to sedentary lifestyles that the majority of kids are exposed to in most developed countries – any movement is probably better than no movement.  But if you want real, measurable results and the best bang for your buck – you really can’t beat strength training.

So should you expect, say, an eight-year-old to exercise with barbells and kettlebells?

To answer this question, let’s quickly revisit the science behind resistance exercise and the original cause of fears surrounding kids and free weights.

Fears around weight training for kids

Where does the belief that weight training stunts growth come from?

In 1990, the American Association of Pediatrics (AAP) issued a cautious statement that “children and adolescents should avoid the practice of weight lifting, power lifting and body building”.  The reason was vaguely defined as weight lifting’s potential to lead to injury, although it was admitted that no proper data was available to make a firm conclusion.  Included in the list of potential musculoskeletal injuries were epiphyseal fractures.  To understand the potential adverse effect of such fractures, you need to know a few facts about epiphyseal (growth) plates.

Growth plates are cartilage plates present at both ends of long bones (arms, legs, fingers, collarbones, etc.).  Under normal conditions, through childhood and adolescence, bones grow through cellular division at those growth plates – new cells get pushed towards the centre of the bone (lengthwise) and ossify (harden) leading to its elongation. In adults who have stopped growing, growth plates “fuse” after cell division at these sites stops.

Growth plates are weaker than joints and bones around them, so – when a bone is subjected to sudden excessive and abnormal mechanical force – they often become primary sites for fractures.  This poses a high risk of their abnormal remodeling and development to the point of cessation of cellular division and, thus, stunted growth.

The fear behind kids and weightlifting was stemming from a belief that when growth plates are subjected to too much stress, they may get compressed, crushed or otherwise damaged, triggering abnormal ossification and, therefore, slowing down or preventing normal growth.

Although AAP subsequently revised its original position and is now stating that “Appropriate strength-training programs have no apparent adverse effect on linear growth, growth plates, or the cardiovascular system” (as backed by many observations, evidence and studies), most people continue to be excessively overprotective when it comes to allowing children to exercise with free weights.

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The fact of the matter, however, is that one-third of all growth plate fractures occur during participation in competitive sports such as football, basketball, or gymnastics and about 20% of all growth plate fractures occur during participation in recreational activities such as biking, sledding, skiing, or skateboarding.  The cause of epiphyseal fracture is typically a sudden impact to the joint (a fall or a blow).  Proper lifting does not subject bones and joints to such forces.

In fact, in one retrospective evaluation of strength training injuries incurred by 13 to 16 year olds, it was revealed that strength training (and competitive weightlifting) were remarkably safer than other sports, such as soccer, basketball, and football.

Interestingly, competitive sports mentioned above were never singled out as causes for epiphyseal fractures.  Which is counterintuitive, when you consider ground reaction forces – after all, such “routine” activities as running and jumping (common in competitive sports) subject the bones and joints to a tremendous amount of stress.  Running, for instance, may subject the bones to repetitive stress equal to 3-6 times bodyweight at its peak, while jumping may increase that stress to up to 10 times bodyweight.  A child weighing only a 100 pounds, therefore, may, at times, subject the bones in his legs to up to 1000-pounds of force (often – for a single leg)!  When this is applied to normal childhood play and sports, the impact becomes even greater. Throwing, tackling, jumping out of trees and falling of jungle gyms exceed any stress on a young athlete’s bones that strength training.

This cannot even be remotely compared to forces that children’s bodies would experience during controlled lifting – plus, whatever impact they do experience is of much shorter duration.  Weight training for kids helps build muscle, tendon, and ligament strength to help protect the athlete from these ground forces. If an athlete is not engaged in a proper strength and conditioning program, the chance of injury actually increases.

Do you still think lifting weights is more dangerous compared to football or basketball?

Reality check: benefits of weight training for kids

The benefits of weight training for children are pretty much the same as those for adults:

  • Increase in muscular strength better prepares them for challenges of the everyday life. This doesn’t necessarily mean that they can now join a circus to demonstrate spectacular feats – stronger and more resilient muscles mean less injury in everyday play situations;
  • Resistance training provides an outlet of sorts to utilize the extra energy most kids get these days from food. This is a much broader topic for discussion (and, as mentioned, you still can’t let them eat anything they want just because they exercise, as the repercussions of eating the wrong kind of food span much farther than just extra “calories” that you need to burn) – but, everything else being equal, it is still a better option;
  • As we covered in the past, exercise does not just positively impact muscles – it also positively impacts bones, resulting in the increase in bone density. This makes bones less brittle, once again, preventing potential injuries from everyday play.  What’s even more important, National Institute of Arthritis and Musculoskeletal and Skin Diseases defines osteoporosis as “a pediatric disease with geriatric consequences,” because the bone mass attained in childhood and adolescence is an important determinant of lifelong skeletal health. The health habits your kids are forming now can make, or literally break, their bones as they age. Accumulation (“banking”) of bone tissue during childhood and adolescence will provide a bigger buffer against bone loss when they get older.
  • The expectation here is that the child will continue resistance training and structured exercise well into the adult years to continue reaping the health benefits. Early introduction to strength training and lifting weights will make transition to more adult-appropriate exercise much easier.  As the child approaches adolescence and the endocrine system catches up, allowing muscle size development and improved recovery – this solid foundation of efficient muscles and strong bones obtained during childhood will allow significantly better adaptation to that transition.  When kids become adults and start moving on to really heavy weights (still, relative to their personal level, of course) – efficient motor units and perfected exercise technique positions them much better for further development and personal records.  Young adults will then be able to lift more and better.  As you know by now, development and growth of muscles is stimulated by unusually high loads that they do not typically experience every day – such stressor triggers adaptation mechanisms that overcompensate to prepare for similar potential future stress and lead to muscle growth.  We have previously addressed the importance of sufficient lean muscle mass as anti-aging strategy, body composition control and purely from aesthetic perspective (this is really a win-win scenario from multiple angles) – adults need to do this anyway, so why not prepare earlier and make it easier?
  • The benefits of weight training for children go beyond the physical. At the time when many kids struggle with this, weight training and the resulting strength development can boost self-confidence, decrease chances of depression and improve social skills.

 

Weightlifting and children: rules and guidelines

Exercise for kids has to be approached with caution.  Remember, the focus is on creating a solid foundation, rather than beating world records.  Precisely because of different recovery pathways, you can’t really overload a child’s system with things like extreme endurance or any sort of high intensity training protocols.  Endurance is a product of having a higher number and more efficient mitochondria to support extreme demands for energy delivered through oxidation of fat.  While, in theory (and in practice), exercise that places unusual demands on the child’s aerobic energy system does, in fact, improve mitochondrial function, kids really aren’t built to train for ultramarathons.

Can kids get stronger lifting weights?  Absolutely – but that strength is typically developed slightly differently, compared to adults.  With adults – increase in muscular strength comes from a combination of neuro-muscular adaptation (and, as a result – more efficient recruitment of muscle fibers) and, very importantly, an increase in the actual size (and number) of those muscle fibers.  In other words – strength training in adults is typically accompanied at least by some degree of muscular hypertrophy.  Such hypertrophy is largely supported by androgenic hormones – something that pre-pubescent children typically lack.

By contrast, with children, under the age of puberty, because the levels of growth-promoting hormones are significantly smaller, strength gains happen differently – primarily through neuromuscular adaptation and improved recruitment of motor units.  This doesn’t mean, by the way, that strength gains cannot happen for someone lacking androgenic hormones – as is often demonstrated by women  and the elderly (with both groups typically lacking  androgenic hormones at the levels exhibited by young males).  It can, but through a different kind of adaptation.

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Not only are the benefits of weight training for kids the same as for adults, but free weights often remain the only feasible way to train kids, since exercise machines are typically built for adult bodies.  In most cases, it is difficult for a child to maintain proper form and technique while using exercise machines that do not accommodate shorter limbs.

How should you approach weight training for kids?  Here are a few simple rules:

  • Weight training for kids should focus on short focused sessions that place sufficient demands on musculoskeletal system, thus developing muscle and bone strength and efficiency. Kids cannot typically follow the same frequency and manner of progressive resistance exercise sessions that adults use to boost through their plateaus (like laddering, drop sets, etc.) using strenuous heavy weight exercise;
  • The length of an exercise session would depend on age. Aim for 5-10 minute sessions for younger kids and add some more time, if necessary, as they grow older and progress.
  • To make it even clearer – children should not exercise at their maximal capacity. The goal here is not to go after personal records every several weeks (as it might be with adults, who have a much better biology to recover from those in a relatively quick time) – the goal is to provide enough extra muscular stimulation to drive progress, but not to a point when the child remains sore for two weeks after and is either unable to exercise at all or, even worse, exercises before fully recovered and gets injured. Children should work with a resistance that will allow them to perform no fewer than about eight repetitions (in other words, with children, emphasize slightly lighter weights and slightly higher reps);
  • Proper sleep and recovery in general becomes PARAMOUNT – as it is for adults, of course, but even more so, for children, since increased levels of physical exercise will demand more recovery time. There should be at least one full day of rest between exercise sessions.
  • Warm up is as important for kids as it is for adults. The purpose of a warm-up is to get the blood flowing and prevent injuries.  Resist the temptation to omit warmup because the weights involved are low – relative to a child’s strength, they are not.  Warmup with very light weights (or no weight at all) will also pre-activate the nervous systems and muscles and will result in more efficient recruitment of muscle fibers.   Young children’s training should always start unweighted or with PVC pipe.  This lets them understand and fine-tune the technique without  the dangers  associated  with  weight-loading;
  • Body-weight exercises, (eg, push-ups, sit-ups, etc.) are great for beginners. Developing initial abdominal and shoulder muscle strength through such bodyweight exercises can help reduce the likelihood of back and shoulder overuse injuries when the real strength training program begins;
  • With young kids under the age of 13, adherence to specific structured protocols and extreme control over technique might be difficult – this is why the presence of a qualified coach with experience in working with children is very important.

This last point is a good segway into  the next question:

At what age should children start weight training?

Although you can start simple bodyweight exercise with children at any age (as soon as they are able to follow basic instructions), introducing structured free weight exercises (regardless of the actual weight) may be challenging, because until a certain age children may lack physical and emotional maturity to take advanced instructions and the discipline to stick to them.  Shorter attention span means it is harder to keep children engaged.  So, realistically, an appropriate age for building the foundation for resistance weight training would be around 7 or 8.  In the end, children should be sufficiently mature that they can respond to coaching advice, and will behave appropriately (follow instructions and respect their fellow trainers).

Even so, kids’ exercise sessions should be short (15-20 minutes) – but with greater emphasis on having them do the right type of exercise.   Children have to be supervised all the time during their weight training sessions and any mistakes with form should be corrected promptly. Once again, since children are more susceptible to injury with their muscular systems still underdeveloped, cheating or sacrificing technique for higher weight/rep targets is unacceptable here.

That said, if a child is able to perform more than 12-15 repetitions of a given lift with proper form, the weight should be increased (but not beyond the point that will make a minimum of eight repetitions unobtainable).  Increments in resistance are as important as with adults.  With children, such increments will probably be represented by smaller percentage increases and the overall progress may be slightly slower, too – but the effect will be there.  In fact, strength increases in pre-adolescent children of up to 50% in as little of 12 weeks of structured training have been previously documented.

Of course, the closer children get to puberty, the more they can train like adults, as their bodies become better equipped to deal with increased level of exercise-related stress.  At any age, this weight training does not preclude in any way unstructured physical activity throughout the day – playing with friends, running around and just being kids.

Conclusion

Just like with adults, weight training for kids does not just abruptly stop when they get a little stronger.  Exercise – structured and unstructured – should remain a life-long endeavour.  Of course, even if they temporarily stop, kids may have a better ability and more time to pick up where they left off.  But studies also demonstrated rapid and significant decreases in upper- and lower-body strength (19.3% and 28.1%, respectively) in preadolescents who previously trained for 8 weeks – as quickly as only 8 weeks after training ceased.  Interestingly, participation in sports such as football, basketball, and soccer did not maintain the training-induced strength gains that were developed during the resistance-training program.

The effect of “detraining” is very real – in kids, too.  This, of course, doesn’t mean you should push them beyond their abilities to progress all the time and score points just for bragging rights.  It’s not about that.  What it is about is building a proper foundation – and continuing building upon that foundation as the time goes by and the child develops into an adult.

So go ahead – get your kids a set of light weights (and a good trainer, if you can’t rely on yourself) – and start them on this wonderful journey of being stronger, leaner, smarter and all-around healthier.