Analysis of the effect size of overweight in muscular strength tests among adolescents. Reference values according to sex, age and BMI
The aim of this paper is to quantify the effect size of overweight on the results of muscular strength tests in adolescents and to report percentile tables based on sex, age and BMI. The study hypothesized that the effect size obtained from the difference between normal-weight and overweight youth would be greater than the differences between sexes within the same age group. A total of 11044 Spanish adolescents (48.5% girls) aged 14.39 ± 1.21 years (range: 12-16 years) from 42 secondary schools participated in the research. Muscular strength was evaluated using standing long jump, hand grip strength (manual dynamometer) and sit-ups (30 s). The effect size was analysed using the adjusted Hedges' ğ. The results show that 76.3% and 72.8% of overweight boys and girls respectively performed a standing long jump equal to or less than the normal-weight average. The 67.4% and 67.1% of overweight boys and girls respectively showed manual dynamometer values equal to or greater than the normalweight average. Finally, 68.7% and 65.9% of overweight boys and girls respectively obtained measures for 30 s of sit-ups equal to or lower than the normal-weight average. It can therefore be concluded that the differential effect size between boys and girls is higher than that between normal-weight and overweight adolescents in the three strength tests analysed. In spite of the above, these results suggest the value of taking into account BMI when assessing the muscular strength of young people, in addition to sex and age.