n South African Journal for Research in Sport, Physical Education and Recreation - Analysis of effect size of overweight in flexibility among adolescents: reference values for physical education according to gender, age and BMI

Volume 41 Number 2
  • ISSN : 0379-9069


The aim of this study was to quantify the effect of being overweight on flexibility in adolescents. The study sample consisted of 10036 Spanish students (4920 girls; 5116 boys) aged 12–16 years from 42 secondary schools. Flexibility was assessed using the sit-and-reach test. The effect size was analysed with the adjusted Hedges’ ğ. Girls had higher flexibility scores compared to boys, regardless of their weight class. When compared to participants of the same gender (all ages combined), overweight girls and boys did not have greater flexibility scores that their normal-weight peers. However, the average flexibility scores of 59.8% and 61.4% for overweight girls aged 12 and 13 years old, respectively, were found to be higher than their normal-weight peers of the same age were. The differential effect size between normal-weight and overweight adolescents was no higher than that between boys and girls for the flexibility test analysed. Overweight girls aged 12–13 years had higher average flexibility scores (60%) than their normal-weight peers. BMI remains a predictor of sit-and-reach test performance. The percentile values for gender, age and BMI are reported.

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