Strength training for children

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There are many benefits of strength training for children while the risks are limited. That is, if it happens under the right guidance. In this first part, I will address the alleged risks and how to minimize them. In the second part of the series, I will discuss the guidelines given for strength training for children. Finally, in the third part, I will delve into the specific benefits of strength training for children and how to maximize them.

Strength Training for Children

Recently, I posted a video on Facebook of two Russian children doing some Calisthenics and posing. My wife’s reaction was:

“That can’t be good, it will inhibit the growth of those boys!”

The idea that strength training at a young age would limit growth is something you hear often. However, if you ask why, you often don’t get a good answer.

It’s such a dogma that gets repeated over and over again and thus becomes “truth” without any substantiation.

Another commonly heard but rarely substantiated statement is that children may engage in strength training “as long as they use body weight as resistance.”

In this article, I will specifically address these two commonly heard statements, but also discuss research on the real risks of strength training for children in general.

“Children should only train with body weight”

I have always considered this to be a silly statement for a simple reason:

“Body weight” says as little about resistance as any random dumbbell if you don’t specify which exercise it is, the way it is performed, and who is performing the exercise.

As is so often the case, wrong guidelines arise because someone applies certain rules to the wrong situation, I suspect the same mistake is being made here. If we look at well-known exercises like pushups, pullups, and situps or crunches, I understand such a statement because for many young children, these are exercises with relatively little resistance.

However, this does not apply to all children. During the pull-up, for many children, the body weight is already too much resistance. They cannot pull themselves up or can only do so a few times, indicating that the resistance is too great.

Moreover, it is often seen that the increase in age is not accompanied by a similar growth in strength when children reach puberty and have never done any form of strength training before that time. When I teach Kobudo (armed martial arts) at secondary schools, I am always amazed at how much trouble most of them have doing just 10 pushups.

They have to do this “as punishment” when they drop their weapon, but especially as a control measure so that those bouncing teenagers don’t do crazy things with the training weapons. If they start by asking what a pushup is, you can imagine that they have some difficulty with it. When these are the boys with the biggest mouths in the group, I always find it amusing to stir them up a bit by joining in, but with one arm, possibly with a chest slap. However, I find it even more fun when a girl sees her chance to assert herself and very demonstratively shows the boy in question that those 10 pushups are nothing.

After all, one body is not the same as another. One person is simply stronger in absolute terms than another, or in relative terms (strong but very much body weight). Also, at a later age, of course, it is much more difficult to lift a body with a fat percentage of 20% than a body with 5% body fat. Also, whether or not to train legs, for example, makes a considerable difference in exercises with body weight as resistance. Why do you think you see so many boys and girls who do Calisthenics, so exercises with body weight, never train legs? They see that only as extra, dead weight that they have to lug around when they want to impress on the playground with their tricks.

Then there is the way of execution. I have often mentioned the term “ego-lifting” to refer to all those forms of conscious, poor technique to move more weight. This usually manifests itself in half movements that are performed too quickly. Just see how many pushups you can do when you are allowed to do the upward and downward movement in 1 second and how many you can do when you have to do this for 10 seconds.

The degree of resistance in strength training is usually expressed as a percentage of the weight with which you (during a certain exercise) can do one repetition, the so-called 1RM (“One Repetition Maximum”). If I do a pull-up on one arm, that one repetition is also the only thing that works, if it works. During the pull-up with one arm, my body weight provides 100% 1RM as resistance, possibly more if it doesn’t work. The pushups on one arm only account for 2% of my 1RM since I can do 50 of them. So, my body weight as resistance can provide 50 times more resistance during one exercise than that same body weight during another exercise. The boys in the first video shown do push-up variants like the “planche pushup” which are much more difficult than normal pushups and therefore cannot be compared with them.

“Body weight as resistance” can never be a guideline because “body weight as resistance” is not a fixed given, but a variable given depending on the person, type of exercise, and method of execution.

“Strength training for children limits growth”

Children should not engage in strength training because it could limit growth. If this were the case, many sports clubs would have a problem. Sports such as gymnastics, soccer, and basketball, where bones and joints are repeatedly subjected to great pressure, offer a much greater risk of damaging growth plates (1).

The growth of our bones takes place in a specific part of the long bones (such as the thigh and shin, upper and lower arm) called the epiphyseal plate, or growth plate. These long bones consist of the middle part called the diaphysis. Where this begins to widen is called the metaphysis, while the ends are called the epiphyses.

When you are still “growing,” the metaphysis and epiphysis are separated by the growth plate. This consists of cartilage that has not yet calcified. This is the place where new bone tissue forms, allowing you to grow as a child. The growth spurt you experience during puberty is mainly caused by the increase in sex hormones such as testosterone and estrogen and increased release of growth hormone. Growth ultimately stops due to calcification of the growth plate.

Damage to the growth plate can limit further bone growth from that point forward (2-5). In fact, the repair of the damage through a so-called “bone bridge” is what can inhibit growth. However, a significant trauma is required for this (such as a fracture), and even then, the number of cases in which growth is inhibited is limited to a small percentage (5).

Various studies have shown that strength training for children, both adolescents and younger, does not excessively stress growth plates (1,6,7). At least, when done through a well-developed training program, focused on the young athlete and their body.

“A well-designed strength training program following the recommended loads, sets, and repetitions appropriate for the young athlete’s age and body habitus should not excessively stress growth plates.”

K. Dahab”, Johns Hopkins Hospital, Baltimore

In those rare cases where damage to growth plates is related to strength training, it is attributed to incorrect technique, incorrect weights, improper use of equipment, and lack of qualified supervision (8,9,10).

Furthermore, I described in an article last week that the correct pressure (and execution) in strength training makes women’s bones stronger, thus preventing problems later in life (11). This also applies to children (12). Overprotecting children from stress can actually cause problems.

So, the same applies to children as it does to adults: Choosing the right resistance prevents a lot of problems.

General Risks of Strength Training for Children

Even if we look beyond growth problems, the risk of strength training for children seems to be very manageable.

“A training program under good supervision does not pose a greater risk than any other sport or activity for children” (13). When “the guidelines” for strength training for children are followed, it is both safe and effective (1,13,14,15,16). The guidelines referred to here are those of: The American Academy of Pediatrics (14), the American College of Sports Medicine (15), the American Orthopaedic Society for Sports Medicine, and the National Strength and Conditioning Association.

Damage to growth plates is therefore very limited compared to other sports. Other injuries such as (lower) back problems are often caused by poor technique and can be prevented by proper guidance (1,13)

Summary, Proper Guidance is Important!

The statement that children can do strength training as long as the resistance is formed by their body weight is incorrect. Body weight as resistance is a variable factor depending on the person, type of exercise, and method of execution.

The statement that strength training can stunt growth in children is incorrect or at least exaggerated. Strength training poses less risk to growth than other regular sports.

The most important thing in strength training for children is that it is done under the right, qualified guidance. With the trend that the “basic concept” is being adopted by more and more gyms and thus there is no longer any guidance for members, extra attention needs to be paid to this. Parents who give their children a gym membership would therefore be wise to invest a little more in guidance. Good chance that this extra expense can be saved on physiotherapy later on.

Guidelines for Strength Training for Children

Strength training for children can be done safely and effectively when done according to the right guidelines. Below we discuss these guidelines as established by various American institutions.

In the section above, I already discussed misconceptions regarding this topic such as limited growth and body weight as resistance. Most of the risks feared can be mitigated with the right guidelines. When you look at all the recommendations for strength training for children, you will hardly see any difference from the recommendations for adults.

Doctor’s Advice & Medical Declaration

The American institutions* advise to first request a sports examination or medical advice from the general practitioner before starting strength training (1).

In the Netherlands, you can request a sports medical examination (or “sports inspection”). For participation in certain sports, a sports inspection is mandatory (such as boxing and diving), but this is also useful for children who start with strength training. It provides insight into whether there are any medical objections to this. A sports inspection is done by a sports physician. The costs for this are covered by the health insurance for children up to the age of 18 (17).

* These institutions include the American Academy of Pediatrics (AAP), American College of Sports Medicine (ACSM), American Orthopaedic Society for Sports Medicine (AOSSM), and the National Strength and Conditioning Association (NSCA).

Literature References

1. American Academy of Pediatrics, Strength Training by Children and Adolescents, Pediatrics, 2008; 121; 835-840.
2. AAOS, American Academy of Orthopedic Surgeons. The Injury Prevention Program, 1994.
3. Caine, D., et al., Does weight training increase the risk of injury to the growth plate? In: Strength and Power in Sports, P.V. Komi (Ed.), Blackwell Scientific, London, 1992, p. 369-376.
4. Micheli, L.J., Strength Training by Children and Adolescents, in Pediatrics, 2008; 121; 835-840.
5. Parikh SN, et al., Injuries in Youth Football: National Emergency Department Visits During 2001–2013. Orthopaedic Journal of Sports Medicine, 2016; 4(9).
6. Myer, G.D., et al., The Back Squat: A Proposed Assessment of Functional Deficits and Technical Factors that Limit Performance, Strength and Conditioning Journal, 2014; 36(6): 4-27.
7. Rians, C.B., et al., Resistance Training for Children and Adolescents, in Sports Health, 2010; 2(6): 470-483.
8. Rowland, T.W., Strength Training by Children and Adolescents, Clinical Journal of Sports Medicine, 2001; 11(2): 133-140.
9. Rowland, T.W., The Case for Strength Training by Children and Adolescents, Pediatric Exercise Science, 1990; 2(4): 294-303.
10. Yesalis, C.E., et al., Exercise Physiology, in Pediatrics, 1998; 101: 785-787.
11. Heijer, den. The Correct Pressure (and Execution) in Strength Training Makes Women’s Bones Stronger, Preventing Problems Later in Life, 2024.
12. Algra, B. Good, Hard, and Healthy, 2024.
13. Fountain, T., A. Riebeling, and R. Blomme, Strength Training for Children and Adolescents, American Family Physician, 2006; 74(5): 849-856.
14. Bird, S.P., et al., Strength Training for Prepubescents: Is It Safe? Strength and Conditioning Journal, 2009; 31(6): 20-22.
15. Greene, D., Is Resistance Training Safe for Prepubescents? ACSM’S Health & Fitness Journal, 2013; 17(4): 29-34.
16. Rowland, T.W., Exercise Physiology in Pediatrics, in Nelson Textbook of Pediatrics, 1996; 13th Edition.
17. Rowland, T.W., Short-term Effects of Strength Training on Growth and Maturation in Prepubescent Boys, Medicine and Science in Sports and Exercise, 1990; 22(5): 605-609.
18. Zwolski, C., et al., Adolescent Female Athletes’ Views on Sports Nutrition and Related Health Care, Journal of Nutrition Education and Behavior, 2015; 47(4): 376-383.e1.

I am personally in favor of open, honest information provision and will not unjustly demonize anabolic steroid use. My experience is that you are not listened to when it is clear that you are insufficiently informed and give unfounded advice to someone considering using anabolic steroids. They are more likely to listen to the “experienced experts” they see around them using than to parents or a coach who clearly have no knowledge of the subject. However, I differ in opinion on this point with, for example, the doping authority, which called an article of mine on anabolic steroid use “pro-steroids” because I stated that it can be used safely in theory if a number of conditions are met that are hardly met in practice.

Personally, I would point out to my child that genetics, nutrition, and training are the most important factors in achieving certain physical performances. “Give yourself a few years to see where these take you.” In some cases, you will find that your natural predisposition and efforts were sufficient to achieve your goals, and you will see that you did not need anabolic steroids. In other cases, you will find that you did not even come close to your goals, and anabolic steroids will not make up for this difference. Anything in between must make this consideration themselves, always questioning to what extent the goals are too high or the predisposition and effort too low.

I would also make it clear to my child that anabolic steroid use can be discussed no matter how strongly I am against it. I would want to know what my child is using or considering using and demand that my child be able to tell me everything about it in detail. He/she should be able to give a presentation about the type of steroid and all possible effects. It surprises me every time as a natural bodybuilder that I know more about specific anabolic steroids than some of the people using them. In many if not most cases where anabolic steroid use goes wrong, it is due to a lack of knowledge.

Summary

• A sports examination is recommended for medical complications before starting strength training (by youths).
• The minimum age to start strength training varies and depends on the child’s development.
• A training program should be individualized based on goals, time, and background.
• Always have a warm-up and cool-down.
• Avoid training at maximum strength (1RM) due to the high load and risks.
• Let children use free weights unless machines are adjusted to their height.
• Regarding exercise order: Large muscle groups before small ones, Complex exercises before simple ones, exercises involving multiple muscle groups before exercises for isolated muscle groups.
• Maintain the correct training volume and schedule in terms of number of days, exercises, sets, reps, and rest.
• Discuss the use of anabolic steroids.

Children can increase their strength by 30 to 50% in just eight to twelve weeks of strength training. In addition to other positive effects on athletic performance such as jump height and sprint speed, overall health is also improved.

However, strength training must be well thought out and conducted under qualified supervision.

Benefits of Strength Training for Children

The benefits of strength training for children are significant and diverse. In addition to an increase in strength, bone strength can increase, balance can improve, cholesterol can improve, body fat can decrease, and lean body mass can increase. It can also increase self-esteem. There are even studies showing that strength training improves daily functioning and self-esteem in children with cerebral palsy.

The greatest value that I attribute to sports at a young age in general and strength training in particular is that it teaches the habit of a healthy lifestyle. It is not surprising that many people who sit overweight on the couch and feel powerless to do something about it are often the same people who used to come to gym class weekly with a note from their parents. These differences are already very strong at that age between children who exercise and children who do not. Simply the experience of pushing yourself further than the point of fatigue, pushing your limits by running longer or faster, or moving more weight. These are things that people who have never exercised in their youth often look at with a look as if the athlete is the one who is crazy.

There are exceptions of people who only see the sporting light later in life, become addicted after seeing the first results, and cannot imagine living any other way than sporty. Although these are often the most inspiring stories, they are the exception to the rule. Due to the disadvantage incurred in youth, they will have a much more difficult start, but often have to do more for the same result even afterwards.

I will elaborate on some of the mentioned benefits of strength training for children.

Increase in Strength

It is obvious to first look at the actual effect of strength training on children’s strength.

Children can increase their strength by 30 to 50 percent in just eight to twelve weeks of strength training. To maintain this strength, they must do strength training at least twice a week. This increase in strength disappears when not trained for more than six weeks. In pre-pubescent children, it has been shown that muscle activation from nerves, speed, and pattern of activation increase strength, not an increase in muscle mass.

It used to be thought that strength training for children who have not yet reached puberty is not effective (in terms of increasing muscle strength) because they have insufficient androgens (“masculinizing hormones”) such as testosterone for hypertrophy. Hypertrophy is an important, if not the most important form of muscle growth, by providing muscle cells with new nuclei with which they can hold more plasma and thus become larger. I have mentioned before that the first gains in strength through training are almost always caused by an improvement in muscle activation by the brain and nerves and not by the muscles themselves becoming larger. Muscle strength therefore always increases earlier than muscle mass.

Increase in Muscle Mass

Once children have reached puberty, the increase in muscle mass is enhanced by strength training. This is not surprising since the amount of male (and female) hormones then increases. Even after puberty, children have more androgens and exercise (not necessarily strength training) leads to hypertrophy and thus more muscle mass. In pre-pubescent children, however, there would be no increase in muscle mass.

Research results seem unanimous on this last point. However, if you look at the images of the children in part I of this article, you cannot ignore that these children have more muscle mass than the average child of their age. This can lead to several conclusions.

The parents and trainers of these children have them follow a different training protocol than is mentioned in the studies, possibly combined with better nutrition. Nutrition is not mentioned in most studies. After all, gaining muscle mass is about the holy trinity: Training-nutrition-rest. So it may be that the parents and trainers of these muscular children simply follow the same protocol as for adult strength athletes regarding nutrition.

Another option is, of course, that these children, however unlikely at that age, are already being administered anabolic steroids. With this, they can be on the same amount of androgenic steroids as adults, or even higher, which would confirm the researchers’ conclusion that this amount of androgens is needed. Of course, it cannot be ruled out, but one would hope that no parent allows an barely 8-year-old child to use anabolic steroids, let alone actively facilitate this.

A final option, finally, is that some children simply have enormous predisposition and show muscle mass that is not achievable for normal children. These children are not famous for nothing. Precisely because they are an exception, they receive a lot of attention. It is known that some people have very high natural testosterone levels, or for example have an inactive myostatin gene, which means they do not have this natural limiter of muscle mass. The Belgian “Belgian Blue” cows, for example, are known for being extremely muscular because this gene has been deactivated by genetic manipulation. The amount of creatine phosphate, an important supplier of energy, also varies from person to person. Many use creatine as a supplement, while for some it is pointless because they are already at a maximum naturally.

Strength Training Also Reduces Body Fat in Children

When researchers in 1997 had both boys and girls aged 11 to 12 do strength training for twelve weeks, this also reduced their body fat. Although the circumference of various body parts increased (in contrast to the control group), the thickness of the skin folds decreased (again in contrast to the control group). This can only mean that lean mass has increased. The researchers found this effect remarkable because it had to come mainly from strength training. Only 5 minutes of cardio was done for warming up and cooling down. Personally, I do not find this so remarkable, I am in favor of strength training to reduce body fat in the long term. However, it can be considered remarkable that this effect occurs in such a short term.

In a study ten years earlier, the fat-burning properties of strength training by children were also demonstrated.

Increase in Jump Height

Strength training for children is often recommended by coaches to continue working on improving athletic abilities outside of the sports season. Many athletes incorporate strength training to improve attributes such as jump height, beneficial for sports like basketball or soccer.

In a study involving 6- to 8-year-old karate athletes, researchers had them engage in strength training twice a week for 40 minutes over 12 weeks. Tests conducted before and after the training showed no significant difference in running speed or flexibility. However, there was a notable increase in horizontal jump height compared to the control group.

Another study compared the results of strength training in 52 pre-pubescent children (both boys and girls) with a control group of 39 children. The training group underwent sessions three times a week for 12 weeks, resulting in significant increases in jump distance for both genders.

The impact on vertical jump height remains inconclusive, with varying results from different studies. However, there is evidence indicating an increase in vertical jump height in children due to strength training.

Increase in Sprint Speed?

Short-distance sprint speed (up to 30 meters) also improves with strength training, although the increase is smaller compared to strength gains.

A study involving young football players divided them into two groups: one receiving football training combined with strength training and the other only football training. After 12 weeks, the group with strength training showed improvements in sprint speed over both 10 and 30 meters. However, the increase was relatively small compared to the significant strength gains observed.

“It seems that a combination of strength and speed training may be more beneficial for speed development. It should be noted, however, that based on the data of our study, the transfer of strength gain to speed was rather small (58.8% increase in leg strength vs. 2.5% in 30-m speed)”

M. Christou, Democritus University of Thrace

In a study focusing on jump height, researchers also examined sprint speed, this time over a distance of 30 yards (approximately 27.5 meters). The increase in speed was observed only in girls.

Strength Training for Children: Conclusion

This series has demonstrated that strength training for children carries no more risks than for adults, provided it is done under proper supervision and follows established guidelines.

In conclusion, the various benefits of strength training for children include:

• Increased muscle strength
• Development of muscle mass during puberty
• Reduction in body fat
• Improved jump height
• Enhanced sprint speed
• Increased bone strength
• Improved cholesterol levels
• Enhanced self-esteem
• Better balance

With all these benefits in mind, parents may now consider enrolling their children in a suitable strength training program.

References

1. Conroy BP, Kraemer WJ, Maresh CM, et al. Bone mineral density in elite junior Olympic weightlifters. Med Sci Sports Exerc. 1993;25:1103-1109.