There’s a significant amount of information out there on how to train various populations, including children, so rather than focus on what to do I thought it’d be interesting to understand why. Most common perceptions about both the efficacy and safety of various resistance training programs is based on a large body of research focused primarily on adults. Children, however, require special consideration specifically around the period associated with puberty before any of those conclusions can be applied to said population. Understanding the differences in physiological responses to exercise between children and adults is a vital part of the equation when it comes to program design. Several biological and physiological changes during this period are behind the varied adaptations and include: variance in growth rate both from child to child and children compared to adults, differences in motor skills competencies, variance in levels of bone ossification, differences in levels of key hormones such as testosterone, and psychological differences to name a few (Earle et al, 2008).

According to Blimke in his article Resistance Training During Preadolescence Issues and Controversies (Blimke, 1993), children make similar percentage gains in strength compared to adults however on an absolute basis they are much smaller. Additionally, the increase in strength is not generally associated with hypertrophy (getting bigger) as it is with adults but instead linked more to changes in intrinsic contractile characteristics of their muscles and increased levels of neuromuscular activation. These adaption changes make perfect sense and the author further speculates that improved motor coordination, in addition to activation, also accounts for the difference. However, as with adult populations, short term resistance training has no effect on height or weight changes (acceleration/deceleration for children).

These are important response differences for the strength coach when it comes to proper goal setting and adjustment of the resistance training program as time progresses. For example, without the knowledge that strength gains are primarily the result of neuromuscular adaptions as opposed to hypertrophy for adults, a child may experience disappointment due to a lack of realistic expectations around their resistance training program. Or, a coach may alter a prescription in attempt to solicit hypertrophy gains but instead unwillingly/unknowingly put the child at increased risk for injury. Although a properly designed resistance training program for children would not involve significant amounts of high intensity exercise, research shows that children are indeed more susceptible to central nervous system fatigue than adults. In a 2007 study, it was determined that during a period of two-minute maximal muscle velocity contraction, both boys and girls showed depressed rate of contraction over their adult counterparts (Streckis et al, 2007). This doesn’t mean that strength coaches can’t incorporate high intensity exercise into the resistance program for children but understanding this difference should help the coach program not only the proper intensity, but account for adequate recovery as well (more than they would for their adult populations).

Neuromuscular adaptions are primarily behind strength gains in children and resistance training programs, however, motor unit activation is hypothesized to be potentially responsible for all other observable adaptation deltas including hormonal response, glycolytic capacity, substrate utilization and VO2 kinetic. Other notable differences include intramuscular synchronization, volitional activation and agonist-antagonist co-activation however these too are thought to be related to the notion that children are less capable, substantially so, of fully engaging their type II motor units (Dotan et al, 2012). Again, understanding how the adaptions differ between adults and children as well as where the limitations are with the latter are critical in safe and efficient resistance training protocol.

Over aggressive programs that may be appropriate for well understood adaptions in adults are not appropriate for the types and levels of adaptations seen in children. The risks associated with prescribing a resistance training program for children without a solid understanding of the responses to training that are unique to this population can be minimized both by understanding these differences in response/adaption as well as following some basic guidelines (Earle et al, 2008):

• Children and parents should be education about the benefits and risks of resistance training
  
• Only properly trained strength and conditioning professionals should design and monitor resistance training programs for children
  
• Proper warm-up, equipment selection/size/fit and cool down procedures should be followed
  
• Resistance should only be increased slowly and as technique progresses
  
• Initially, at least, only 2-3 non-consecutive training sessions should be scheduled
  per week
  
• Proper periodization models should be applied to all program design aspects
  

REFERENCES

Baechle, Thomas R.,Earle, Roger W.. (Eds.) (2008) Essentials of strength training and conditioning /Champaign, IL : Human Kinetics,

Blimkie, C.J.R. (1993). Resistance Training During Preadolescence Issues and Controversies. Sports Medicine 15: 389. https://doi.org/10.2165/00007256-199315060-00004

Dotan, R., Mitchell, C., Cohen, R., Klentrou, P., Gabriel, D., & Falk, B. (2012). Child—Adult Differences in Muscle Activation — A Review. Pediatric Exercise Science, 24(1), 2–21.

Streckis V, Skurvydas A, Ratkevicius A. (2007) Children are more susceptible to central fatigue than adults. Muscle Nerve. 36:357–363. [PubMed: 17487867]