Strength training for kids and adolecents

Is weight training safe, or is it harmful for children & adolescents? What is the right age to start weight training? What is the best type of program for children & adolescents?

Key points:

  • Many young athletes miss out on reaching their athletic potential because they don’t lift weights.
  • Lifting weights, and in particular squatting, improves bone mineral density and growth rather than stunting it.
  • Researchers suggest athletes may begin training as early as age 6.
  • Strength increases of up to 30%-50% may be elicited in the first 8-12 weeks of untrained participants.
  • Initial percentage based strength increases in children are equivalent to adolescents and adult untrained populations.


  • Children: 6-12 years old
  • Adolescents/Teens: 13-18 years old
  • Synonyms: Strength-training, weight-training, resistance-training.

When it comes to training youth, I have trained my fair share. To this day, 40%-50% of my clients are youth aged.  Over the years, I’ve had many parents express their concerns when their son/daughter begins weight training. Usually the parent is coming to me because members of their son’s/daughter’s sports team have started training and are showing increased performance results– these parents are intrigued and interested in what I’m doing for other kids, but are still on the fence about their own children participating.  These hesitant parents have 1 or more of the following 5 things to express to me:

  1. I don’t want my son or daughter lifting heavy weights yet.
  2. I don’t want him/her to stunt his/her growth.
  3. I don’t want him/her to become slow from lifting heavy weights.
  4. I want him/her focussing on running and bodyweight movements for now so he/she can become quicker.
  5. I don’t want him/her to get hurt.

It’s only natural to have the best interest of your son or daughter at heart. The last thing that you or he/she needs is an injury, especially when the whole purpose of working out is to improve performance and reduce risk of injury in a given activity, not to hinder performance or get injured outside of the sport that they are training for.

So let me address a few of these concerns and myths:

Myth: Weight training stunts growth.

If you are wondering where this myth originated from, or if there is research supporting it, I’ve found that most sources have linked the origins of this notion to an old study that took place in 1964, by Kato & Ishiko (1).

The study examined adolescents and preadolescents in remote areas of Japan who performed heavy labor in mountainous villages for several hours a day while being exposed to a very poor diet that lacked adequate nutrition.  From this study it was deduced that weight training could elicit the same effects as the children in Japan being exposed to heavy labour for prolonged periods with poor nutrition, and therefore disrupt growth plates resulting in decreased stature. This notion (weight training stunts growth) was spawned from anecdotal findings and has zero scientific evidence backing it.

If you want your son or daughter to excel in athletics with today’s level of competition, the right time to begin weight-training is a lot sooner than you think.

So what is the truth about lifting weights? There is a plethora of studies that support the countless  positive effects that weight training has on children (refer to table 1), perhaps the most noteworthy effect that scientific evidence supports is contrary to what the common myth (stunted growth) suggests and that is –  weight training actually increases bone health, density and growth in children and adolescents (2).

Benefits derived from resistance training:

  • Increase muscle strength
  • Increase muscular power
  • Increase local muscular endurance
  • Increase bone mineral density
  • Increase cardiorespiratory fitness
  • Improve blood lipid profile
  • Improve body composition
  • Improve motor performance skills
  • Enhance sports performance
  • Increase resistance to injury
  • Enhance mental health and well-being
  • Stimulate a more positive attitude towards lifetime of athletics

When can my son/daughter begin weight training? Researches suggest that youth may begin training and learning movements as early as age 6 in order to accumulate “training years” and motor skill leading to efficient movement patterns (3). This will eventually allow youth to train heavier sooner and best case scenario have more than 10 years experience behind them by the time they are 18-19. The take away point is that the earlier youth start strength training the more of a head start they can get on their peers.


Children – Although Some muscle gain may be possible to children it is not the main cause of strength gain. Children have such low levels of androgens (testosterone) before they reach puberty, the strength gains are contributed to increased neuromuscular coordination -the ability to activate and recruit motor units which control muscle fibre (4) (5).

Adolescents– Strength gains for adolescent trainees are attributed to increased coordination (intra muscular coordination) and  increased muscle mass (hypertrophy)-the body is now able to produce higher levels of androgens than when a child.

So how much stronger can my son or daughter become before puberty? Is it even worth it? It has been observed that children may increase strength by 30%-50% in 8-12 week period.Percentage based strength gains are equivalent to those of adolescent and adults (6)!  So yes it is very worthwhile to begin training early.

Injury prevention for sports: According to the American College of Sports Medicine, an estimated 50% of all injuries sustained by youth while playing sports could be prevented if more emphasis was placed on developing fundamental fitness abilities prior to sports participation (6). Risk factors such as poor physical condition and muscle imbalances can be identified and treated prior to participation in sports (preseason) vastly decreasing injury rate.

Myth: Your child/teen is likely to get injured weight training.

A growth  plate fracture has not been reported in any prospective study that was competently supervised and appropriately designed. If resistance training programs are conducted by qualified instructors and are planned with age-specific needs in mind, the risk of joint injury is negligible. However, if established training guidelines are not followed, accidents and injuries are possible (Risser, 1991). Coaches, teachers, and trainers must be aware of the inherent risk associated with resistance training and should attempt to decrease this risk by following established guidelines (6)(7).

Myth: Weight training will make you slow. Running speed is influenced by how much force an athlete can apply to the ground. The fastest way to improve this is to increase lower body strength. Moderate to heavy loads in the squat, depending on the athlete, will strengthen the quads, glutes hamstrings and calves to produce  more ground reaction force .A recent study study performed on elite rugby players showed that increases to maximal squat strength made the player’s sprint times significantly faster (8)


  1. If your son/daughter is old enough to participate in organized sports, they are old enough to begin “learning how to train” by practicing body-weight calisthenics and incorporating resistance band work.
  2. Adherence to more formal training programs with traditional weight requires emotional maturity and the ability to follow directions. Researchers suggest 7-8 years old.
  3. Weights should remain “light” to “moderate” with high reps for the first 2-3 years of training to practice technique, build confidence and establish good movement patterns.
  4. Save heavy weights for individuals with a “training age” of 2-3 years. That means 2-3 of gym experience.
  5. Organized and well monitored strength training increases athletic performance in sports and vastly reduces risk of injury.


  1. *Kato, S. & Ishiko, T. (1964). Obstructed growth of children’s bones due to excessive labor in remote corners. In s. Kato (ED.), Proceedings of the international congress of sports sciences (PP. 476). Tokyo: Japanese Union of Sports Sciences.
  2. Morris et al., 1997
  3. Washington, 2001
  4. Ozmun, Mikesky, & Surburg, 1994; Ramsay et al., 1990
  5. Faigenbaum, Avery D. President’s Council on Physical Fitness and Sports Research Digest: Youth resistance training. Series 4, No.3. September 2003.
  6. Smith, Andrish, & Micheli,1993
  7. “Are changes in maximal squat strength during preseason training reflected in changes in sprint performance in rugby league players?” Journal of strength and conditioning research. March 26, 2012.

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