We received a great reaction to our post on resistance training in children, as the CSEP position paper affirmed the benefits of strength training for pre-adolescents. A popular belief among parents is that strength training can stunt growth in pre-adolescents, but there appears to be little research to back this claim. A recent paper published by Michalldis et al. (2012) adds another dimension to this paradigm by examining the effects of plyometric training on athletic performance in pre-adolescents (mean age 10.6 years).
45 children were randomly assigned to control group (CG, n = 21) who performed regular soccer training, and the rest were assigned to a plyometric & regular soccer training group (PTG, n = 24). The intervention lasted for 12 weeks during the in-season period of soccer training. The PTG performed a mixture of jump based training twice per week, and pre and post experiment measures in each of the following performance tests: speed (0-10m, 10-20m, 20-30m), leg power (static jump), counter movement jump (CMJ), depth jump (DJ), standing long jump (SLJ), multiple 5-bound hopping (MB5), leg strength (10RM), anaerobic power (Wingate test) and soccer specific performance tests.
The results showed that PTG produced significant increases in all speed tests and all vertical jump tests (p < 0.05). SLH, MB5 and CMJ all increased significantly (p < 0.05), and so too did leg strength and soccer specific performances (agility and ball kicking distance). Interestingly, anaerobic power did not increase in the PTG group.
So plyometric training can induce positive training adaptations in pre-adolescent boys aged 10. What is interesting to note is that each performance test is influenced by a strong neural input, which indicates that a learning effect and/or more efficient communication between nerve & muscle is taking place in this population. Pre and post anthropometric measures were not taken, therefore the effects of any natural growth or maturation cannot be estimated. However, we can probably rule out any significant alteration in muscle phenotype (upregulation/downregulation of muscle enzymes) having occurred as no significant improvement was noted in mean anaerobic power.