THE EFFECTIVENESS OF RESISTANCE TRAINING IN CHILDREN - A METAANALYSIS

Many recent studies have reported that resistance training can be effe ctive in producing strength gains among prepubescents. These studies a ppear to refute the early claims of ineffectiveness of resistance trai ning in children. A meta-analysis procedure combines the results of in dividual empirical studies and estimates a standardised effect, termed effect size. This effect size is based on the scores of the control a nd experimental groups before and after training. It defines the diffe rence between the gain of the experimental and control groups, divided by the standard deviation of the pooled variances of both groups. A l iterature search revealed 28 studies which described a resistance trai ning programme for girls and boys under the age of 12 and 13 years, re spectively. Presumably, these children were pre- or early-pubescents. However, only 9 of these studies provided the necessary data to calcul ate the effect size and could be included in the analysis. The majorit y of the studies showed a gain in strength between 13 and 30%. The ove rall mean effect size was found to be 0.57. This signifies that follow ing training, the average child in the resistance training group was a bove 71.6% of the children in the control group. The effectiveness of resistance training can be influenced by factors such as age and matur ation, gender, as well as the frequency, duration and intensity of the training programme. The studies included in the analysis examined par ticipants of varying ages and did not demonstrate a dear influence of age. Most studies examined only boys or a mixed group of boys and girl s. Therefore, the influence of gender on the effectiveness of resistan ce training in prepubescents cannot yet be determined. Nevertheless, i n the few studies where boys and girls were examined separately, no di fference was found in the effect of resistance training between gender s. It appears that a training frequency of twice per week is sufficien t to induce strength gains in children. However, the minimal, or for t hat matter optimal, duration and intensity are not clear. Some of the weaknesses observed in the reviewed studies include. (i) the lack of c ontrol for a possible learning effect; (ii) non-randomisation into the training and control groups; (iii) no report of adherence rate; (iv) a reliance on boys as study participants; and (v) too little informati on on the type, volume and intensity of training. Future studies shoul d take these weaknesses into consideration.