Effect of after‐school physical activity on body composition in primary school children: The Slovak “PAD” project

Physical activity is associated with many physical and mental health benefits. This study aimed to investigate the effect of a 24‐month after‐school physical activity intervention on body composition in normal‐weight children. Participating students (6–7 years of age at baseline) were divided by reason of their parental preference to intervention and control groups. Children in the intervention group (n = 20; 10 boys and 10 girls) followed an aerobic training program (two 60‐min sessions per week), whereas children in the control group (n = 20; 10 boys and 10 girls) participated in the usual practice. Body composition characteristics were repeatedly measured by means of bioelectrical impedance method. At 2 years, finally, intervention boys had a smaller rise in BMI (mean difference, MD: −0.97 kg/m(2), p < 0.05), BMI z‐score (−0.44, p < 0.09), body fat % (BF%) (−6.47%, p < 0.01), and fat mass index (FMI) (−1.32 kg/m(2), p < 0.001) than controls. In girls, however, the intervention program induced no significant differences (p > 0.9) in the measured variables compared to controls at the final follow‐up (MD: −0.04 kg/m(2) for BMI and −0.01 for BMI z‐score). Changes in BF% and FMI in a positive direction occurred at 18 months (MD: −3.38%, p < 0.05 and −0.99 kg/m(2), p < 0.01, respectively), but did not persist over time (p > 0.07). In addition, no significant changes (p > 0.07) in the fat‐free mass index were associated with the physical activity intervention in either boys or girls. In conclusion, compared to the controls, a long‐term physical activity intervention in boys was associated with a significantly smaller rise in BMI and improvement of body composition by reducing both BF % and FMI. In girls, however, this intervention did not result in any statistically significant changes in body composition variables.