Changes in physical activity and motor skills
CRF
CRF
Linear mixed models showed an intervention effect of 15.5 min (95%CI: 4.5,26.6) in children’s daily MVPA at intervention schools between t0 and t1 compared to controls (Fig. 
Forest plot of adjusted mean differences with 95% confidence intervals for outcomes (see additional files For the power calculation of the MVPA and CRF outcome, we assumed a cluster size of n = 12 and n = 15 students per class, respectively. Power calculation resulted in a study sample of n = 552 with n = 46 clusters (i.e., classes) to detect an achievable between-group difference of 11 min per day of MVPA and a sample of n = 300 with n = 20 clusters (classes) to detect a between-group difference of 62 m on the 6-min run. Further details can be found in ‘Sample size calculation for a future definitive trial’ [Additional file 5].