It is not uncommon for parents of young athletes to ask me about the safety and effectiveness of weight training for kids. Several studies in recent years have shed light on the safety aspect, but a study published in Pediatrics tries to determine the effectiveness of resistance training in kids. In the study, Behringer et al. perform a meta-analysis of prior studies performed with children and adolescents. The author notes, “…the main purpose of our study was to examine the influence of age and maturity on the effectiveness of progressive resistance training among children and adolescents.”
The authors reviewed 42 studies with 1728 total participants, with an average age of 11.5 and average body weight of 101 lbs. Most of the programs consisted of 2 or 3 sets per exercise, with 8 to 15 reps per set and the weight set between 60% and 80% of maximum.
They found that the overall effect size demonstrated that strength training is effective in childhood and youth. While the trainability of muscle increases with age, effects are seen in prepubertal children. And girls demonstrated gains just as the boys did. What is interesting is that there was no appreciable spike seen at puberty. Rather, there was a linear increase seen with longer training programs. This finding suggests that children can gain muscle strength separate from neuromuscular adaptations that were thought to be the main benefit of resistance training before puberty.
I think that there are several take home messages from this study, especially for those of you with young athletes. First, resistance training does, in fact, increase the trainability of muscle, and subsequently muscle strength. The effect does increase with both age and maturity. However, the effect seems to be related to the duration of training rather than simply hormonal changes at puberty. “We found that a greater number of training sessions per week is associated with higher strength gains after resistance training and that long-term interventions are more beneficial than short ones,” Behringer concludes.
So I think that it is reasonable to conclude that weight training for kids can be effective, and that there is no minimum age required. Kids need to be mentally prepared for resistance training, perform a training program appropriate for their bodies, gradually advance over time, and have adequate supervision. Increasing the number of training sessions per week and sticking with the program over longer periods can produce greater results.