Old wives tales No.2: Does weight training in children stunt growth?

Should your child be 'lifting weights' before puberty?

Childhood obesity is on the rise throughout the world, with over 30% of kids in some countries being overweight.  Today children are more sedentary than ever before, resulting in earlier age of obesity, type 2 diabetes, high blood pressure and other diseases seen in adults.  The guidelines are clear: children need moderate to vigorous exercise for at least 60 minutes a day, and three of these days should include muscle and bone strengthening activities.  But what about children who cannot run because they are too overweight--how do they perform strength training exercises?

By the age of ten I had visited a two gyms.  For fun, I would have a go at using the weights machines.  While doing so I never forgot my mother’s words of warning- " lifting weights would stunt my growth."  I think it's fair to say this is a common health belief and one I held myself until September 2015 at the Faculty of Sports Medicine (FSEM) conference, in Dublin.

It was day two of the conference and being seated all day was making me uncomfortable.  A loud, fast, upbeat voice resounded throughout the lecture theatre- it was Professor Avery Faigenbaum all the way from New Jersey and he had everyone’s attention.  He raced through 40 minutes of why he trains children- yes children- to use weights as part of resistance (strength) training, and why resistance training plays an essential role to improve health in a young population with rising obesity.  Prof. Faigenbaum wasn't just talking about kids who were overweight, he was addressing inactivity, also known as ' Exercise deficit disorder', in normal weight children.   Beginning with a smiling eight year-old boy who weighed over 60kg (120lbs),  Prof. Faigenbaum described the boy's struggle to keep up with his peers on the playground.  But that changed.  He was now lifting age-appropriate weights – supervised – and building strong muscle that could better deal with the sugar and carbohydrates who was eating.  And he could move around better.  Even if Body mass index remains high, doing exercise improves health outcomes.

We watched a video of a slender young girl performing bar bell lifts into a lunge position using low weights suited to her training age.  A shy, thin 12-year old boy, who played computer games for 3-4 hours a day lacked basic co-ordination for simple tasks like balancing on one leg.  After four weeks of Resistance training, under supervision, he began to build confidence, co-ordination and strength. 

This type of co-ordination should have already developed by early adolescence in children with normal brain development, but physical educators in the USA will tell you that core muscular strength and motor skills are on the decline; the cause- inactivity (Faigenbaum et al., 2002). 

Exercising the brain to exercise.  We only have one window of opportunity to do so!

As children grow so, too, do their brains.  The developing brain reinforces pathways that are being repeatedly used or stimulated and prunes those that are not being used (Myer et al., 2015).  Prof. Faigenbaum emphasised the importance of this window of neuronal (nerve) development, which before the age of computers would have been stimulated regularly through working and playing outside (Myer et al., 2015). 

Unlike adults, who have reached puberty and therefore have higher levels of testosterone, children develop strength mainly through neural stimulation i.e. activating, through use, the nerves that attach to the muscles and getting the brain accustomed to this action.

the distinction in definitions between "weightlifting,"  and "resistance or strength training."

  • Weightlifting is defined as the sport of performing the snatch, clean and jerk lift of a heavy weight.

  • Resistance or Strength training involves exercise against a resistance such as the body's own weight, lifting dumbbells, or against an elastic band.

So who should be doing resistance training and why?

There is now compelling evidence from studies in children and adolescents that regular resistance training improves fitness and health (Lloyd et al., 2014).  Prof, Faigenbaum has done numerous studies in children using resistance/strength training.  He has shown that in children aged 7-12 years old, two supervised resistance training sessions a week are required to improve strength and co-ordination, and reduce injury rates while playing other sports (Faigenbaum et al., 2002).  The recommendations are to use low weights and perform a high number of repetitions i.e. 15-20 lifts of a weight.

The 2014 International Consensus on Youth Resistance training

This position statement concluded that supervised resistance training in children and adolescences is safe and does not negatively affect the growth of children.  They explain that childhood is the time to build strong healthy bones through weight bearing activities.  But, trainers or physical education teachers must take each child individually to assess their technique and current fitness level before performing these exercises. 

Weight lifting is addressed as part of a resistance training programme.  Studies show that supervised weightlifting exercises cause less injuries than playing competitive sports or other resistance training activities. 

I contacted Dr Greg Myer, an author of the 2014 international position statement on resistance training, to clarify the minimum age a child could begin resistance training.  He confirmed that: "it is when the child can take instruction which is often around 7-8 years of age." (Myer et al., 2013)

If your child is a girl she is almost 50% less likely to exercise than her male peers, putting her at increased risk of ill health.

Advantages of doing resistance training from Age 7 on-wards

Health benefits:

  • Healthy heart and lungs
  • Reduces body fat
  • Reduces diabetes, as muscle becomes more sensitive to insulin
  • Improved bone health
  • Reduced back pain (Auvinen et al., 2008).
  • Better health later in life
  • Improved social and self- confidence

Physical benefits:

  • Improved strength and jumping ability.
  • Improved co-ordination
  • Improved motor skills
  • Reduced injury rates while playing other sports
  • More likely to exercise later in life

What kind of exercises should children and Adolescents do?

Exercise guidelines for children and adolescents

If you’re a Doctor who sees kids, a physical education teacher, or a parent, then I invite you to read 2014 International consensus on Youth Resistance Training (Lloyd et al., 2014).

If you’re from the USA then your guidelines, most of which are based on studies from before 2008, do advice resistance (strength) training activities at least 3 times a week for kids, but they do not explain how to carry these out.

The Canadian paediatric society guidelines recommend specific weight lifting programmes from the age of 10-years old on-wards.  They advice supervised lifting of small free weights, with high repetition (15-20), good technique and avoid lifting heavy weights (Lipnowski and LeBlanc, 2012). They also state that if a child spends > 2 hours watching TV each day they are twice as likely to be obese.

In the United Kingdom, the department of health recommendations on the www.Gov.UK website, do not give instructions on prescribing an age appropriate resistance-training programme (See below).

The UK department of health (DHSSPS, 2011) recommend exercises for children age 6-18 should include:

  • Aerobic: 60 minutes or more each day of moderate to vigorous exercise such as playing football, running, cycling, playground activities

  • Muscle-Strengthening:  As part of their 60 or more minutes of daily physical activity, children and adolescents should include muscle-strengthening physical activity on at least 3 days of the week e.g. pulling and pushing activities, playing on playground climbing frames.

  • Bone-Strengthening: As part of their 60 or more minutes of daily physical activity, children and adolescents should include bone-strengthening physical activity on at least 3 days of the week e.g. playing tennis, hopping, skipping, jumping.

But what about resistance exercises?

So, if the national guidelines do not reflect the 2014 international consensus statement how do we ensure our children can take part in supervised resistance training programmes? 

In the UK and Ireland Physical education time has decreased.  Unless your child’s school has an equipped gym with adequate staff to teach these exercises it means sending them to a physical trainer who can provide this service. 

Dr Myers and his colleagues have developed a training model called Integrative Neuromuscular Training (INT)(Myer et al., 2015).  INT includes resistance training, plyometrics (jumping), core stability and agility exercises under supervision.

If a child has never trained before, then their training age is Zero.  Introductory supervised exercises include:

Muscle warm up:

  • Scapular Press-ups
  • Box jumps and landing
  • Exercise band Pull-ups
  • Exercise band Pull-downs
  • Plank

Main resistance exercises:

  • Over head Squats
  • Elevated Press-up (Horizontal position)
  • Pull-ups using TRX belts (H0rizontal position)

Stretching:

  • All the main large muscles

The above plan includes most of the exercises used in the INT programme ( Myers et al.,2013).

Summary

  • Sixty minutes of daily moderate to vigorous aerobic exercise is important.  But, for some children running around is not easy or achievable.  So, resistance training is an attainable goal that improves general health and fitness for all children.
  • Resistance training in childhood reduces injuries while playing other sports, improves health later in life, and increases likelihood of exercising when older.
  • Children are becoming more sedentary, watching TV for > 2 hours a day.  We need to remember how children used to play- this involved a lot of running, lifting, pulling ropes and jumping; all the foundation for healthy development of muscles and nerves.
  • If we do not stimulate the neuromuscular pathways in the body and brain during childhood, then we will loose this opportunity for optimal neuromuscular development.
  • Obesity in children is increasing.  The cause is multifactorial: consumption of sugar, exercising less, and the effects of maternal diet or blood sugar level during pregnancy.  The solution, along with healthy eating promotion, is to encourage early exercise for all children.
  • Ask your physical education teacher about a resistance/strength training programme for children- earlier the better.


References

(DHSSPS), D. O. H. A. S. S. A. P. S. 2011. Start Active, Stay Active: A report on physical activity for health from the four home countries’ Chief Medical Officers

AUVINEN, J., TAMMELIN, T., TAIMELA, S., ZITTING, P. & KARPPINEN, J. 2008. Associations of physical activity and inactivity with low back pain in adolescents. Scand J Med Sci Sports, 18, 188-94.

CAREY, N. 2012. The Epigenetics Revolution: How modern biology is rewriting our understanding of genetics, disease and inheritance. Icon Books Ltd.

FAIGENBAUM, A. D., MILLIKEN, L. A., LOUD, R. L., BURAK, B. T., DOHERTY, C. L. & WESTCOTT, W. L. 2002. Comparison of 1 and 2 days per week of strength training in children. Res Q Exerc Sport, 73, 416-24.

LIPNOWSKI, S. & LEBLANC, C. 2012. Healthy active living:Physical activity guidelines for children and adolescents. Canadian Paediatric Society, Healthy active living and sports medicine committee, 17, 209-10.

LLOYD, R. S., FAIGENBAUM, A. D., STONE, M. H., OLIVER, J. L., JEFFREYS, I., MOODY, J. A., BREWER, C., PIERCE, K. C., MCCAMBRIDGE, T. M., HOWARD, R., HERRINGTON, L., HAINLINE, B., MICHELI, L. J., JAQUES, R., KRAEMER, W. J., MCBRIDE, M. G., BEST, T. M., CHU, D. A., ALVAR, B. A. & MYER, G. D. 2014. Position statement on youth resistance training: the 2014 International Consensus. Br J Sports Med, 48, 498-505.

MYER, G. D., FAIGENBAUM, A. D., EDWARDS, N. M., CLARK, J. F., BEST, T. M. & SALLIS, R. E. 2015. Sixty minutes of what? A developing brain perspective for activating children with an integrative exercise approach. Br J Sports Med, 49, 1510-6.

MYER, G. D., LLOYD, R. S., BRENT, J. L. & FAIGENBAUM, A. D. 2013. How young is too Young to Start Training? HEALTH & FITNESS JOURNAL, 17, 14-23.


Siobhan Graham