This article discusses the benefits and risks associated with strength training for children. It also outlines how to compile a safe and effective resistance programme for children and adolescents.
The UK's Strength and Conditioning Association recently published a position statement on resistance training for young people that dispels many of the surrounding the negative impact it may have on the immature skeleton. Part 1 of this article discusses the benefits and risks as well as what effects it can have on performance. Part 2 (below) explains the principles of compiling a safe and effective resistance programme for children and adolescents.
Strength Training For Children Part 1: Benefits, Risks and Performance
You can find a summary of the key facts at the end of part 1.
The media in the UK has been full of alarming reports regarding rising obesity and decreasing levels of fitness in our children over the past few years. Lloyd et al. adds to this by pointing out that recent evidence also shows a decrease in muscular strength levels of school-age children.
Resistance training has been shown to have a positive effect on musculoskeletal health, body composition and cardiovascular risk factors.
Fears that resistance training would harm the growing skeleton of children and adolescents have thus far not been supported by clinical observations. In fact, research has indicated that childhood may be the opportune time to build bone mass by participating in weight-bearing physical activity.
Resistance training may further be of specific benefit to overweight children. Endurance exercise is normally prescribed to help with weight loss but the researchers argue that excess body weight may be an obstacle to performing activities such as jogging. It has also been found that overweight children seem to have decreased motor control and an increased injury risk compared to their peers, which may make strength training a safer option initially.
Their view is that the inclusion of a structured strength training programme into a weight loss programme, can help children improve their motor skills and muscle strength while gaining confidence in their physical abilities. It will also help increase muscle mass which adds to a healthier body composition.
Injury prevention benefits
There is a growing body of evidence that appears to show that participation in regular resistance training by young athletes lead to a reduction in acute and overuse injuries over the competitive season as well as a shortened rehabilitation period if injured.
Qualified supervision and appropriate training loads are however essential to prevent young athletes from sustaining injuries through resistance training. Researchers investigating acute injuries related to resistance training found that 77.2 % were accidental and that most could have been avoided with appropriate supervision and a focus on technical competency.
Multifaceted programs that increase muscle strength, enhance movement mechanics and improve functional abilities may be the most effective strategy for reducing sports related injuries in young athletes. These programs further seem to be more effective if implemented in younger age groups – before the onset of neuromuscular deficits and biomechanical alignment issues.
The researchers recommend that children should build a good basic strength, motor control and fitness base before they start taking part in competitive training. Incorporating basic jumping activities into free play can for instance strengthen their muscles and tendons and prepare them for sport in later life. The problem is that all the evidence these days suggest that kids are less active and do not spend enough time playing outside, which may mean that the musculoskeletal system of aspiring young athletes are ill prepared for their sport.
The focus with strength training in children and adolescents should thus be to first produce an individual with balanced muscle strength and good muscular control, before they specialise in a specific sport.
A well supervised programme may also help children overcome the loss of coordination and muscular control that they typically experience when they go through a sudden growth spurt.
In general injury records show that female athletes of all ages may be predisposed to certain injuries (e.g. anterior cruciate ligament rupture (ACL)) compared to their male counterparts. This is thought to be in part due to differences in biomechanics displayed between female and male athletes.
Researchers have found that young female athletes who participated in strength training as they matured demonstrated fewer of the injury risk factors e.g. increased knee angles with landing.
A recent meta-analysis of all the available literature revealed that an age related association between resistance training and a reduction of ACL injuries may exist in that strength training only reduced ACL injury incidence when it was implemented between the ages of 14-18.
There is evidence that various forms of resistance training are capable of improving young athletes’ performance in:
Change of direction speed
General motor performance (jumping etc.)
The research on this topic is still open for debate. It does seem to suggest that multi-faceted programs inclusive of resistance training may have psychological benefits as long as self-improvement and enjoyment remain central to the training programme.
Excessive volumes of physical training could however lead to negative psychological effects and if the recovery time between training sessions are inadequate it can cause overtraining syndrome. Overtraining syndrome leads to changes in the biological (injury), neurochemical (depression) and hormonal systems (sleep disturbances) and a child can take a very long time to recover from this. See my post on overtraining syndrome for details on how to manage and prevent this condition.
Summary Part 1
Resistance training is safe and beneficial for children as well as adolescents.
Attention to postural alignment and technical competency during all exercises is essential to prevent injury.
It can help increase bone mass and muscle mass and help with weight loss in overweight youths.
It can effectively reduce the injury risk over a competitive season and aids recovery from injury.
It has specific benefits for injury prevention in young females with best results gained when implemented between the ages of 14 to 18 years.
Resistance training can enhance performance in various activities (running, jumping, etc.)
It may also have a positive psychological effect as long as enjoyment stays central to a programme. Excessive volumes of any sport can lead to overtraining and have negative psychological effects.
Part 2: Developing a strength training programme for children
How does muscle strength develop in childhood and adolescence?
As children reach the onset of puberty they experience rapid growth along with non-linear gains in muscular strength. Strength gains during childhood are thought to be mainly due to the maturation of the central nervous system (how well the brain and nerves control the muscles) for instance improvements in nerve firing frequency and synchronisation.
Strength gains during adolescence are mostly driven by structural changes to the muscle tissue due to hormonal changes but also include some neural development. Interestingly the number of muscle fibres that one possess is already determined before birth, so any increases in muscle cross-sectional area is largely due to increases in muscle fibre size.
The focus of resistance training in children should thus be based on goals related to enhancement of muscle strength, function and control as opposed to trying to make substantial increases in muscle size which will only happen during puberty.
It is important to remember that children mature at varying rates and that young athletes of the same chronological age can vary with up to 5 years in their biological status. A young athlete should thus be trained according to his biological status. The athlete’s training age should however also be taken into consideration. A technically proficient athlete should not be restricted to introductory training just because of their age.
Evidence further indicate that the most effective training programmes lasts more than 8 weeks, involve multiple sets and are executed more than once a week. Detraining can occur quickly once training is stopped and it is therefore advised that they partake in some form of strength training all year round.
Weightlifting for young athletes
The research, according to Lloyd et al., suggests that the performance of weightlifting movements as part of a strength and conditioning programme can be safe, effective and enjoyable, provided qualified supervision and instruction are available and progression is based on the technical performance of each lift.
Conditions for safe training:
The child should be mature enough to follow directions
It should be done under the supervision of a qualified professional who is knowledgeable of youth resistance training protocols
Correct technique and posture should be acquired first
Exercises using body weight should be mastered first
Free weights should then be introduced since they appear to stimulate more muscle activation than machine based exercises
Once the youth is technically competent multi-joint, velocity specific activities can be introduced e.g. plyometrics and weightlifting. Once again technique should first be developed using modified equipment and light loads.
High training intensities (heavy weights) at the expense of correct technique will likely lead to acute injuries
High training volumes at any load in turn may lead to overuse injuries
For individuals without prior experience of resistance training: Low volume (1-2 sets) and low to moderate training intensities (≤ 60% 1 RM) for a range of movement patterns should be used. Also note that when children are initially introduced to multi-joint exercises (e.g. squatting) their motor control development benefits more from fewer repetitions (1-3) and real time feedback after each repetition.
Constructive feedback is essential to learn good technique
Once technically competent the prescription should be progressed for example 2-4 sets of 6-12 reps at low to moderate intensity (≤ 80% 1 RM).
As training age and athletic competency progress, periodic phases of low repetitions (<6) at high external loads (>80% 1RM) can be used.
Monitor for accumulated fatigue during a training session to minimise the risk of fatigue –induced technical decrements which could lead to injury.
Rest intervals: Children recover more quickly from fatigue-induced resistance training and are less likely to suffer muscle damage. One minute rest should be enough between sets but this should be increased (2-3min) as the intensity of training increases or if a high level of skill is required.
Training frequency: 2-3 sessions per week on non-consecutive days are advocated to be the most appropriate for children and adolescents. The competitive season should however also be taken into consideration as training volumes may already be high. Depending on the competitive demands of the sport, anywhere between 1 and 3 strength training sessions should be completed every week to enhance or at least maintain previously acquired muscle strength.
Repetition velocity: It basically boils down to technical competence and training age. A youth with limited training experience should perform exercises at a moderate speed to ensure control and good technique. A youth with several months of training experience should be exposed to greater movement velocities in order to develop motor unit recruitment patterns and firing frequencies within the neuromuscular system. Or in normal language, to enable him to produce power quickly as is needed in most sports. When high weights are used, the intention to move it as explosively as possible (even if the movement occurs relatively slowly) is enough to maximise the training effect.
Lloyd, R. S., Faigenbaum, A. D., Stone, M. H., Oliver, J. L., Jeffreys, I., Moody, J. A., et al. (2014). Position statement on youth resistance training: the 2014 International Consensus. Br J Sports Med, 48(7), 498-505.