Can Children and Teenagers Do Strength Training?

Strength and resistance training for young people still meets resistance of its own. Coaches, parents and even facility managers repeat that lifting stunts growth, wears out joints or is simply premature. For an operator equipping a club gym, a school hall, an academy or a rehabilitation centre, the question is very concrete: should a youth section have access to strength equipment at all, and under what conditions? This article reviews what bone development, motor development and the injury data actually say, and what it means when you specify equipment.

Ossification: how bone really grows

The skeleton is the passive part of the locomotor system, and it is the part most often invoked against youth training. Ossification happens through two mechanisms: intramembranous ossification and endochondral ossification. The growth rate of a given bone depends on where it sits in the body and on the developmental stage the body is in, and the individual growth plates of the limb bones contribute unequally to final length.

The dynamics of bone growth can nevertheless be split into recognisable phases:

1. From birth to roughly 5 to 6 years, in both sexes: rapid growth.
2. Up to around 10 years in girls and around 12 years in boys: growth slows.
3. Around 11 to 13 years in girls and 13 to 15 years in boys: the pubertal growth spurt.
4. Up to around 14 to 15 years in girls and 16 to 18 years in boys: rapid growth persists.
5. By 21 years in women and 25 years in men: growth slows and stops.

During the first ten years the long bones grow faster than the vertebrae. After that period, height gain comes more from spinal growth, which continues roughly two years longer than long bone growth.

Follow the argument through. If a developing skeleton ruled out resistance training, nobody should touch an external load before 21 or 25 years of age, since only then is bone growth complete. Very few of the people who say an athlete is too young for weights can name the age at which they think weights become acceptable, and most have no background in programming strength work, nor in ontogenesis or osteogenesis. The objection usually reflects unfamiliarity rather than evidence.

The evidence points the other way. A 1990 absorptiometric study of bone mass in weightlifters aged 15 to 20 found increased bone density, which matters a great deal during a growth period, because weak bone raises the risk of fractures, including pathological ones. A 2006 analysis of 22 studies on pre-pubertal and early pubertal strength training confirmed that strength training does not delay growth in children or adolescents aged 9 to 14.

What about the claim that weightlifters are short because they lifted young? Then children who play basketball or volleyball should grow tall by playing. Causation runs the other way: a shorter body gives optimal biomechanical conditions for weightlifting, just as height is an advantage in volleyball and basketball. Every discipline still contains athletes above and below its average.

Ontogenesis and the windows for motor learning

Human development, or ontogenesis, covers the changes that occur from fertilisation to death: cell division first, then somatic, motor and mental change. Its pace is individual, shaped by genetic and epigenetic predisposition, by the external environment and by lifestyle. The postnatal period is the one that concerns training, and it is usually broken down as follows: the neonatal period of 1 to 28 days, infancy from 2 to 12 months, the post-infancy period from 1 to 3 years, childhood, early adolescence, adolescence, adulthood, the menopausal transition in women, and later life.

Motor ability changes across these stages, and each stage has its own signature.

Newborn and infant

• Pre-motor phase: unconditioned reflexes and vital functions establish themselves.
• Early motor phase: erratic movement, uncoordinated, involuntary, without intent.
• Manipulative movement: fine motor control of fingers and hands.
• The stage ends when walking begins.

Post-infancy (1 to 3 years) and preschool (4 to 7 years)

• Balance and proprioception improve.
• Praxis appears: the ability to perform precise, purposeful movement.
• Gradual shift from concrete image based thinking to abstract thinking, and the intellectualisation of motor activity.
• Hyperactivity and spontaneity, with limited ability to concentrate, alongside real harmony, fluency and rhythmic sense. Around 5 to 6 years comes the first motor peak.

Early school age and further dynamic development (9 to 10 years)

• Concentration improves markedly. The second motor peak arrives at 10 to 11 years in girls and 12 to 13 years in boys, with an extraordinary facility for learning and adapting movement.

Puberty and the juvenile period

• Turbulent change throughout the body, 10 to 12 years in girls and 12 to 14 years in boys.
• The pubertal spurt and increasing sexual dimorphism.
• A temporary dip in physical performance in girls.
• A temporary imbalance between excitation and inhibition.
• The stage closes around 20 to 24 years, when fitness stabilises and movement becomes economical and well matched to the task.

Adulthood and ageing

• Full mental and physical development falls between 20 and 40 years.
• Reduced mobility and narrowing motor interests, with cardiovascular vulnerability appearing in the following decades.
• Beyond 60, skeletal fragility such as osteoporosis and reduced bone density, muscle weakness and atrophy, and dissociation of movement.

Reading those stages the right way round, the motor peaks are exactly when resistance or strength techniques should be introduced, because the purpose at that age is to learn movement patterns. The pay off is neuromuscular coordination, balance, stability, mobility and proprioception. As with adults, technique comes first, then volume and intensity are programmed. A young person learning technique, without a high level of strength, physically cannot execute a movement with a heavy load, so relatively heavy loads are not on the table anyway.

One caution matters for any club running age group sessions: children develop at their own pace, and the younger the child the wider the gap between biological and chronological age. Two children of the same calendar age can be far apart biologically. Selecting methods and loads individually is the coach responsibility, not a scheduling detail.

Strength as a motor ability

In sport theory, strength is one of the fundamental motor abilities, most often defined as the capacity to overcome or counteract external resistance through muscular effort. Physical effort means the work of skeletal muscle together with the functional changes that accompany it. Muscle is notably plastic: it adapts to different degrees of effort. Adaptation means long term, relatively durable change, which reverts towards the initial state once training stops. It includes a greater supply of energy substrates and oxygen to the cells and an increase in muscle cross section, that is hypertrophy, which lets the muscle generate more contractile force. Contractile and biochemical properties of muscle tissue shift so that the work being asked of the muscle is performed optimally and economically.

Muscles form the active locomotor system, and their action is transmitted by the passive one, the bones and the joints that connect them. Their basic function is to develop force, which is how a person interacts with the environment. Every displacement in space, every interaction with an object, requires muscular force. Strength is therefore not an optional extra for an adult or a child. It is a condition of ordinary daily function.

Resistance training is not bodybuilding

Most objections collapse the whole field into bodybuilding. Bodybuilding has a defined sporting objective: shaping body proportions to the criteria of a category or federation through skeletal muscle hypertrophy, with the greatest possible simultaneous reduction of subcutaneous fat so the musculature reads clearly. Its training is dominated by isolated movements performed largely on machines. Performed through incomplete ranges of motion, that kind of work encourages muscular shortening, which can lead to structural imbalance, tissue overload and eventually injury.

Machine based movement is also not functional for an athlete who needs strength work to support another discipline. A machine typically stabilises the body in a fixed position, removing or relieving the stabilising muscles, in a posture that has little to do with whole body work in competition. That form of training is optimal for bodybuilders who prioritise the aesthetics of the physique over physical capacity, in the same way that a marathon runner training is optimal only for a marathon runner. A bodybuilder reducing body fat does not adopt marathon training to do it, even though long, low intensity effort would theoretically serve, because the specific form is wrong. By the same logic, people who want strength in the broad sense do not get it from bodybuilding work, and neither do developing children and adolescents, who should be building whole body physical capacity.

Nor should strength training be confused with the heavy athletics disciplines, olympic weightlifting, powerlifting and strongman, which each have their own specificity. Youth strength training should be built on correctly executed movement, with free weights, through a full range of motion. The first stages teach correct movement patterns matched to individual capacity. Load progresses only once technique is owned. Programming and supervision of the whole process are what make it work.

Who should run youth strength sessions

Strength training for children and adolescents belongs to a personal trainer, a clinical or medical exercise professional, a motor preparation specialist or a strength and conditioning coach. Ideally that person understands ontogenesis and the processes at work in a young body, and knows the teaching methodology for each movement.

What should be avoided is handing strength work to the coach of the sport itself. A football coach or a boxing coach should not be the one taking young players through strength sessions.

Why not

Coaching is a set of narrow specialisms, as many as there are sports. Building experience in one discipline makes you a specialist in that discipline. A boxing coach should know how to teach movement, punching and evasion; a football coach should know how to teach ball handling, receiving, passing and dribbling. Each knows what characterises their sport. Most of the time they have no idea how to programme and lead strength training and cannot teach its techniques. That is not a criticism, it is the definition of a specialism.

What the injury research shows

Descriptive and observational studies reporting the frequency or incidence of injury in adolescents during resistance training, weightlifting or powerlifting converge on the same conclusion: strength training in children and adolescents is significantly safer than many other sports and activities.

Pierce followed 70 weightlifters aged 7 to 16 over one year, covering 1224 competition lifts, and reported no injuries at all. That group trained professionally and performed submaximal and maximal lifts for competition results, which makes the finding stronger rather than weaker.

The 2006 analysis of 22 studies on pre-pubertal and early pubertal strength training included 10 studies that tracked injury. Three injury cases were recorded across the whole set. Myer 2017 reports an average of 0.053 injuries per 100 hours of resistance training. Interestingly, most of those injuries stem from incorrect exercise technique.

So it is not strength training that causes injury, it is how strength training is done. For young people, supervision by the person responsible for the session is decisive, and some of the research attributes injuries specifically to a lack of supervision. This holds for every form of training and every sport: execution raises or lowers injury risk at any age. A 2007 analysis covering children and adolescents in ice hockey, football, basketball, American football, cycling, rugby, baseball, softball, handball, judo and karate found higher injury rates than the weightlifting studies above.

The NSCA position

The National Strength and Conditioning Association recognises and supports the view that many of the benefits of adult resistance training programmes are also available to children and adolescents. The NSCA published its first position statement on youth resistance training in 1985 and revised it in 1996, considering four areas:

• Potential risks and concerns associated with youth resistance training.
• Potential health and fitness benefits of youth resistance training.
• The types and amount of resistance training healthy children and adolescents need.
• Programme design considerations for optimising long term training adaptations.

The position rests on a comprehensive review of the scientific evidence on anatomical, physiological and psychosocial change. It applies to boys and girls who have not yet developed secondary sexual characteristics on the Tanner scale, which stages sexual maturity from morphological characteristics: roughly 11 years in girls and 13 years in boys, Tanner stages 1 and 2. The analysis also includes girls aged 12 to 18 and boys aged 14 to 18, Tanner stages 3 and 4.

On that basis, the current NSCA position states that correctly programmed and correctly supervised resistance training is safe for children and adolescents, and can help to:

• Improve the function of the circulatory and vascular system.
• Improve motor efficiency, which can carry over to results in other disciplines.
• Reduce the risk of sport related injury.
• Improve psychosocial wellbeing.
• Build durable exercise habits during childhood and adolescence.

What this means when you equip a facility

If a club, an academy, a school or a municipal sports hall opens strength work to a youth section, the equipment specification changes in a few predictable ways. Free weight stations and benches carry more of the programme than isolation machines, because the early years are about learning patterns through full ranges of motion. Load increments need to be small enough to progress a 12 year old, not only a senior athlete. Supervision has to be designed into the layout, with clear sightlines rather than equipment tucked into corners.

Whatever the mix, indoor equipment in a facility open to a public should meet EN ISO 20957-1 class S, the professional studio class. Class S is the specification that survives shared, supervised, high frequency use. Our professional strength training machines and weight benches are specified on that basis. For younger age groups and for outdoor circuits designed around children, our outdoor fitness equipment for children sits under the playground standards rather than the adult ones, since equipment intended for children is covered by EN 1176-1, with impact attenuating surfacing under EN 1177.

Frequently asked questions

Does strength training stunt growth in children?

No. A 2006 analysis of 22 studies on pre-pubertal and early pubertal training found no effect on growth in children and adolescents aged 9 to 14, and a 1990 absorptiometric study of weightlifters aged 15 to 20 found increased bone density.

At what age can a young person start?

There is no single date. Biological age diverges from calendar age, especially in younger children. What matters is that the session is programmed and supervised by a competent professional and that technique precedes load.

Is strength training more dangerous than team sport?

The data say the opposite. Reported injury rates for resistance training and weightlifting are far below those recorded for rugby and for the team sports reviewed in 2007, and most reported injuries follow incorrect technique or absent supervision.

Should the sport coach lead the strength sessions?

Preferably not. Coaching specialisms are narrow. Strength work belongs to a personal trainer, a motor preparation specialist or a strength and conditioning coach who knows the teaching methodology and understands youth development.

Are machines suitable for adolescents?

They are a complement, not a foundation. Early training should use free weights through full ranges of motion so that stabilising musculature works. Machines earn their place later, and for specific purposes.

Equipping a youth section

The evidence is settled enough to act on: correctly programmed, correctly supervised resistance training is safe for children and adolescents and improves motor development, bone density and injury resilience. What decides the outcome is the quality of coaching and the quality of the equipment underneath it. Tell us the age groups, the supervision available and the floor area, and we will build a specification and a costed quotation around them. Request a quote and we will come back with a layout and a price.