Welcome back! This is the follow up article of Resistance Training in Adolescents: Part One. As you will know, part one looked at the risk factors and reviewed the overall safety of resistance training in children and adolescents. This article will discuss the health benefits of resistance training in adolescents. I would suggest that physiotherapists that help children and adolescents with their injuries will often prescibe resistance exercises; they might be in the form of a Theraband exercises, body weight exercises (squats, calf raises, etc.) or an exercise with added free or machine weights. Now I know that I strive to be evidence based with my practice and I am sure you are in the same boat! So let’s have a look at what gains can be made with resistance training.
Resistance Training for Strength Gains
Most studies will demonstrate an increase in the performance of assessments that measure strength. Current trends show that the ability to gain muscular strength seems to increase with age and maturational status. Specifically a larger strength gain can be expected in children after the onset of puberty (Behringer et al., 2010). The improvements are generally found to be between 13-30% from 8-12 week resistance training protocols (Falk & Tenenbaum, 1996). However it is often argued that the gains seen should be attributed to the nervous system (increased motor neuron recruitment) and motor learning rather than due to hormones or increase in muscle cross-sectional area (Faigenbaum, 2002; Behringer et al., 2010). Greater strength gains have been correlated with increasing maturity, increased volume (number of sessions/week) and a longer program (i.e. having the program conducted over a greater number of weeks/ months). Where age, gender, number of sets and program intensity did not influence the extent of strength gained in the trials reviewed by Behringer et al. (2010).
Strength gains have been seen in male and female children and adolescents. A 26 week and a 15 month trial of resistance training with females, classified as ‘post-menarcheal’ and between 14 and 17 years old respectively, has shown to significantly increase their strength (Blimkie et al., 1996; Nichols et al., 2001). There have been multiple studies showing increase in strength following a resistance training program in boys.
One study showed the following range of improvements:
- Single maximal repetition of bench press (35%)
- Single maximal repetition of leg press (22%)
- Isometric elbow flexion (37%)
- Knee extensors (30%) (Ramsay et al., 1990)
Recent studies have demonstrated a range of benefits in children with cerebral palsy. This includes increased strength, overall function, and mental well-being (Blundell et al., 2003; McBurney et al., 2003). One study that looked specifically at eccentric strength training in children with cerebral palsy suggests that gains were made with regards to increased torque production and decreased co-contraction (Siobhan et al., 2009).
It should be noted that gains in strength, muscle size, or power are lost approximately six weeks after the cessation of resistance training (American Academy of Pediatrics, Council on Sports Medicine and Fitness, 2008).
Resistance Training to Improve Bone Development
While I have discussed the risk of bone damage that is associated with resistance training I should also point out that resistance training (or ‘weight bearing exercise’) is known to be vital in bone modelling. Resistance training is theorised to encourage bone growth by introducing some degree of bone stress and increasing muscle strain, strain rate and compression (Fleck & Kraemer, 1997). Further studies are still required to determine the long-term benefits of enhancing the ‘bone bank’ in children, however animal trials suggest that bone strength persists into old age (Boreham & McKay, 2011).
Despite post-menarcheal adolescent girls been shown to have a transient increase of bone mineral in the first 13 weeks of a 26 week resistance training trial, there were no significant changes in total body or lumbar spine bone mineral after the full 26 weeks (Blimkie et al., 1996). However, female adolescents, aged 14 to 17, have been shown to significantly increase their bone mineral density (as measured at the femoral neck) with a 15 month resistance training program (Nichols et al., 2001).
In Karim Khan’s on-going push for changes to improve the public’s health he was part of a team that undertook a study to see if there was a critical period for bone response to weight-bearing exercise in children and adolescents. They pointed out that children gain as much bone in the two years around the pubertal growth spurt as they will lose after their adult peak has been reached. The study concludes that during the very early stages of puberty, bone may be particularly responsive to weight-bearing exercise (MacKelvie et al., 2002).
Resistance Training to Reduce Injury Risk
“An ounce of prevention is worth a pound of cure”. While Benjamin Franklin’s quote from the mid 1700’s was actually in reference to the fires of the times, it can certainly be applied to the modern sporting world. As physiotherapists we see the impact of injuries every working day. Part One of this article identifies that unsafe environments, supervision that is not qualified (or a lack of supervision) and inappropriate loading and progressions in volume or intensity can be dangerous. However, well structured comprehensive resistance training programs have been found to offer several benefits that would facilitate reducing injuries. Resistance training programs that include plyometric exercises have shown a possible reduction in the number of anterior cruciate ligament injuries in adolescent girls (American Academy of Pediatrics, Council on Sports Medicine and Fitness, 2008).
A review by Faigenbaum and Myer (2010) discusses how regular participation in a preseason conditioning program, which includes resistance training, may facilitate a reduction in the risk of injury. Comprehensive resistance training programs have been found to improve several outcomes including;
- Movement biomechanics
- Functional abilities
- Sport-related injuries in young athletes
The evidence is quite strong that a multifaceted conditioning program will reduce the number of injuries in adolescent athletes. Regrettably one limitation of this type of intervention study is that it is difficult to characterise the contribution of each aspect of the intervention (Faigenbaum & Myer, 2010). The American College of Sports Medicine (1993) states that 50 percent of preadolescent sports injuries could be prevented and that enrolling the young athlete in strength and conditioning programs would be a large part of that reduction.
Sustaining an injury has been reported to be a reason for young athletes dropping out of competitive sport (Butcher et al., 2002; Humphries, 1991; Slater & Tiggemann, 2010). Unfortunately the research into young athletes’ withdrawal from sport leaves a lot to be desired, as there is a gap in our understanding of the impact of sport injury to retention rates in youth sports. However, improving retention rates by reducing injuries may be another good reason to incorporate a resistance training program.
Please stay tuned for ‘Part Three’ of this post – where we will discuss in more detail more benefits of undertaking resistance training, and also my personal experiences of designing resistance training interventions for adolescents.
What Are Your Experiences?
We would love to know what your experiences have been with adolescents and resistance training? Have you achieved some of these benefits or successfully implemented these interventions in adolescents? be sure to let me know in the comments or you could:
Promote Your Clinic: Are you a physiotherapist or physical therapist looking to promote your own clinic? Check this out.
About the Author
This is another guest post from Christopher Snell. Christopher is an Australian physiotherapist who graduated from Monash University (Melbourne). Professionally he has worked with local level swimming and football (both soccer and AFL) clubs as a sports trainer, strength and conditioning coach and physiotherapist. His clinical interests include acute sports injuries, knee rehabilitation and dry needling. He is currently employed at Waverley Park Physiotherapy Centre.
Photo Credit: John E. Lester
American Academy of Pediatrics, Council on Sports Medicine and Fitness. (2008, April). Strength Training by Children and Adolescents. Pediatrics, 121(4), 835-840.
American College of Sports Medicine. (1993). The prevention of sports injuries of children and adolescents. Medicine and Science in Sports and Exercise, 1-7.
Behringer, M., vom Heede, A., Yue, Z., & Mester, J. (2010). Effects of Resistance Training in Children and Adolescents: A Meta-analysis. American Academy of Pediatrics, 126(5), 1199- 1210.
Blimkie, C. J., Rice, S., Webber, C. E., Martin, J., Levy, D., & Gordon, C. L. (n.d.). Effects of resistance training on bone mineral content and density in adolescent females. Canadian Journal of Physiology and Pharmacology, 1996, 74:(9) 1025-1033
Blundell, S. W., Shepherd, R. B., Dean, C. M., Adams, R. D., & Cahill, B. M. (2003). Functional strength training in cerebral palsy: A pilot study of a group circuit training class for children aged 4-8 years. Clin Rehabil, 17(1), 48-57.
Boreham, C. A., & McKay, H. A. (2011). Physical activity in childhood and bone health. British Journal of Sports Medicine.
Butcher, J., Linder, K. J., & Johns, D. P. (2002). Withdrawal from competitive youth sport: A retrospective ten-year study. Jounral of Sport Behaviour, 25, 145-163.
Faigenbaum, A. D., & Myer, G. D. (2010). Resistance training amoung young athletes: safety, efficacy and injury prevention effects. British Journal of Sports Medicine, 44, 56-63.
Falk, B., & Tenenbaum, G. (1996). The effectiveness of resistance traiing in children: A meta-analysis. Sports Medicine, 176- 186.
Fleck, S., & Kraemer, W. (1997). Designing resistance training programs. Human Kinetics.
Humphries, C. (1991). Opinions of participants and nonparticipants towards youth sport. Physical Educator, 48, 44-48.
MacKelvie, K. J., Khan, K. M., & McKay, H. A. (2002). Is there a critical period for bone response to weight-bearing exercise in children and adolecents? A systematic review. British Journal of Sports Medicine, 36, 250-257
McBurney, H., Taylor, N. F., Dodd, K. J., & Graham, H. K. (2003). A qualitative analysis of the benefits of strength training for young people with cerebral palsy. Developmental Medicine and Child Neurology, 45(10), 658-663.
Nichols, D. L., Sanborn, C. F., & Love, A. M. (n.d.). Resistance training and bone mineral density in adolescent females. J Pediatr 2001;139:494-500
Ramsay, J. A., Blimkie, C. J., Smith, K., Garner, S., MacDougall, J. D., & Sale, D. G. (1990). Strength training effects in prepubescent boys. Medicine Science of Sports Exercise, 22(5), 605.
Siobhan, R., Hamer, P., Alderson, J., & Lloyd, D. (2009). Neuromuscular adaptations to eccentric strength training in children and adolescents with cerebral palsy. Developmental Medicine and Child Neurology, 358-363.
Slater, A., & Tiggemann, M. (2010). Uncool to do sport: A focus group study of adolescent girls’ reasons for withdrawaling from physical activity. Psychology of Sport and Exercise, 11, 619-626.