Effects of a 2-year school-based daily physical activity intervention on cardiorespiratory fitness: the Sogndal school-intervention study.

The aim of this study was to describe changes in children's cardiorespiratory fitness (CRF) following a school-based physical activity (PA) intervention. In total, 259 children (age 9.3 ± 0.3 years) were invited to participate, of whom 256 participated. The children from the intervention school (63 boys, 62 girls) carried out 60-min PA over 2 school years. The children from the control school (62 boys, 69 girls) had the regular curriculum-defined amount of physical education in school, i.e. 45 min twice weekly. One hundred and eighty-eight children (73.4%) successfully completed both the baseline and the post-intervention peak oxygen uptake (VO₂ peak) test. VO₂ peak was measured directly during a continuous progressive treadmill protocol where the children ran until exhaustion. The children from the intervention school increased their mean VO₂ peak (95% confidence interval) 3.6 (2.5-4.6) mL/kg/min more than the children from the control school. This VO₂ peak value was adjusted for both sex and baseline VO₂ peak. Boys and girls demonstrated similar VO₂ peak responses. The intervention, primarily carried out at a moderate intensity, had the biggest impact in children with low initial CRF levels. In conclusion, a 2-year school-based 60-min daily PA intervention significantly improved CRF in children.