“Don’t you know it’s unsafe for kids to lift weights? It will stunt their growth. If they don’t use protective equipment they’ll hurt themselves. It’s just not smart!” - Uninformed Parent
Sound familiar? Chances are, if you’re reading this, you think that’s bullshit. And our mission here is to Battle the Bullshit. But, to win any battle, you need some ammo. Our What the Science Says series will arm you with the necessary knowledge to combat those archaic minds who are doing a disservice to the youth.
We’ll look at the benefits of strength and conditioning, as well as the effective guidelines, as it pertains to children. But, first, before we get through any of that, we are going to discuss the key points of growth and development. These principles are what will guide you, coach, in designing a program specific to the youth athletes you train.
Childhood Weakness: A Global Pandemic
Before we get into the meat of growth and development, let’s first start with stating the obvious. Despite the World Health Organization (WHO) including resistance training as an integral part of youth physical activity guidelines (1), strength in school-aged athletes is decreasing (2) and this decline can be seen through two lenses. From a positive light, if you have the opportunity to empower a child athlete by employing a high-quality resistance training program, you’ll set them apart from their weaker peers and put them on the path to success at an early age. Varsity letters, state championships, and scholarships...all benefits of developing athleticism early on.
The flip side of the coin, however, is not as exciting. A weaker youth now means a weaker adult in the future. When you grow up weak, you grow up depending on others to help you, whether that is on the field, around the house, or in battle. And now we’ve got a problem. Thinking long term, we need our children to grow up to be physically independent...athletic dominance is just a bonus.
Boys vs. Girls
Growth is often nonlinear, but you knew that. All of us have a similar story...you went to bed one night and woke up the next day 4 inches taller. Like growth, in-game or physical performance is non-linear as well(3). Although developing muscular strength and increasing sport performance is determined by a combination of muscular, neural, and biomechanical factors (4), both boys and girls typically display linear increases in strength through childhood (5).
The similarity in strength between boys and girls during childhood is mostly due to a maturing nervous system which, in turn, improves motor unit recruitment (6). This is why you regularly see little girls schooling little boys. Up to this point, “chronological age” (how old a kid is) can be used to dictate growth and development.
The gains seen during this stage of development are primarily neural. This point of time is when the nervous system is most rapidly maturing (7). Components of strength such as motor unit recruitment, firing frequency, synchronization, and neural myelination can all be trained at this point (8,9). By simply introducing movement to children, you will get them stronger. As they strengthen, you can stress to progress. But, this is not a green light to be chasing numbers on the bar.
More so than any other stage, you must put the highest priority on movement quality at this stage. Ingraining proper movement patterns when children are young will have a profound impact on their athletic ability down the line. A great opportunity to establish this with your athletes is through warm-ups like those found in the Dynamic Movement Prep series.
Conversely, a lack of attention to movement (i.e. scoring a workout by the number of reps completed or how long it took) will open the door for shitty movement. Practicing shitty movement creates shitty movers. Shitty movers get hurt. Don’t create a shitty mover, coach. This falls completely on your shoulders because kids will want to compete with each other. Reframe the competition. Don’t celebrate the numbers, celebrate the quality of movement. Don’t aim for an arbitrary movement standard, take them to their boiling point without hitting their breaking point. I could beat this horse a few more times, but I think you get the picture.
Boyz II Men: A Tale of Biological Aging
Once kids reach puberty, we see a rapid, non-linear increase in muscular strength (7). In addition to increased strength gains, this is where we will first see young men packing on slabs of meat (10). This change is termed muscular hypertrophy, in which the muscle fiber increases in size allowing for greater force production (11). Though hypertrophy occurs in young women as well, the heightened testosterone levels in young men allow for greater changes, primarily due to sex-specific hormonal changes.
Because the changes differ due to biological factors, at this point in development we start measuring an athlete’s development by their “biological age”. Biological age refers to where the child’s body is in development. Prior to puberty, it doesn’t matter. On a biological level, boys and girls are pretty similar. But after puberty, kids start to develop at different rates. Some boys (@Luke) become men, giants wrecking havoc on the field of play on their way to the 1999 Illinois State Championship. Some...well, some are more like Marty.
Strength gains here can still be driven by the neural factors mentioned above, so movement quality is still the top priority. However, the change in hormone levels will allow for further gains through hypertrophy. You will see a growing disparity between the sexes during this stage of development and the young men will generally outperform the young women in feats of absolute strength. However, you would be doing your athlete’s a grave disservice if you start to “train them like girls”. Though the gap between absolute strength numbers may widen, young women will continue to develop in a linear fashion(3) so stay the course in stressing to progress.
Training Age: The X-Factor
A third age, “training age”, must be taken into account as well. Training age refers to the time an athlete has spent specifically training and is equally as important as biological age (12). This is where black and white can start to become gray. How do we define training? Does it have to be organized training? In a word, “no”. We’ve talked about the benefit of being working man strong before, and the same goes for kids.
How hard to you think it will be to teach a 16-year old kid how to power clean if they’ve spent the last four summers helping their family bale hay? What about a 16 year old kid who has spent the last four summers couch locked playing video games? Training age, in conjunction with biological age, will dictate how you individualize a resistance training program for young men and women. “We fail at the margins of our experience.” If a kid hasn’t been exposed to a movement pattern, regardless of their physical attributes, they will not be able to perform as well as a kid who has seen the movement before. Does that mean we start the poorer mover with empty bar squats until it looks perfect? Again, the answer is, “no”. Heavy loads will expose shitty movement. A proper warm up will allow us to consciously attack and correct these limiting factors prior to loading.
It’s the Principle of the Matter
Alright coach, it’s on you. Before you even begin to think about training children, you must know and understand these principles of growth and development. You have to know that kids won’t be putting on mass before their bodies allow it. You have to stress proper movement regardless of how strong a kid looks. You have to individualize programming based on their abilities. Does it sound difficult? Sure. But the potential negative outcomes if you disregard these principles will be (not could be, WILL be) catastrophic! But we’ll save that for next time.
- World Health Organization. (2012). Global recommendations on physical activity for health.
- Cohen, D. D., Voss, C., Taylor, M. J. D., Delextrat, A., Ogunleye, A. A., & Sandercock, G. R. H. (2011). Ten‐year secular changes in muscular fitness in English children. Acta Paediatrica, 100(10), e175.
- Beunen, G., & Malina, R. M. (2008). Growth and biologic maturation: relevance to athletic performance. The young athlete, 3-17.
- Armstrong, N., & Van Mechelen, W. (Eds.). (2008). Paediatric exercise science and medicine. Oxford University Press.
- Branta, C., Haubenstricker, J., & Seefeldt, V. (1984). Age changes in motor skills during childhood and adolescence. Exercise and sport sciences reviews, 12(1), 467-520.
- Parker, D. F., Round, J. M., Sacco, P., & Jones, D. A. (1990). A cross-sectional survey of upper and lower limb strength in boys and girls during childhood and adolescence. Annals of human biology, 17(3), 199-211.
- Granacher, U., Goesele, A., Roggo, K., Wischer, T., Fischer, S., Zuerny, C., ... & Kriemler, S. (2011). Effects and mechanisms of strength training in children. International journal of sports medicine, 32(05), 357-364.
- Kraemer, W. J., Fry, A. C., Frykman, P. N., Conroy, B., & Hoffman, J. (1989). Resistance training and youth. Pediatric Exercise Science, 1(4), 336-350.
- Ramsay, J. A., Blimkie, C. J., Smith, K. A. R. E. N., Garner, S. C. O. T. T., Macdougall, J. D., & Sale, D. G. (1990). Strength training effects in prepubescent boys. Medicine and science in sports and exercise, 22(5), 605-614.
- Malina, R. M. (2012). Growth. In Encyclopedia of Exercise Medicine in Health and Disease (pp. 376-378). Springer Berlin Heidelberg.
- Neu, C. M., Rauch, F., Rittweger, J., Manz, F., & Schoenau, E. (2002). Influence of puberty on muscle development at the forearm. American Journal of Physiology-Endocrinology and Metabolism, 283(1), E103-E107.
- Faigenbaum, A., & Westcott, W. (2009). Youth strength training. Champaign, IL: Human Kinetics, 139-65.
Currently, Ben is finishing his PhD while serving a clinical faculty member at the University of Louisville, molding the minds that will be the future of strength and conditioning coaches. He also helps support the Olympic Sports side of the Strength and Conditioning Department there as a sports scientist.