Effects of a school based health promotion intervention on physical activity and physical fitness in Ecuadorian adolescents: a cluster randomized controlled trial

Background: We assessed if a school-based intervention improved physical activity, fitness and sedentary behavior among Ecuadorian adolescents. Methods: The ACTIVITAL program promoted physical activity and the reduction of sedentary behavior (mainly screen time) through 15 school classes and awareness raising activities (e;g. walking trail ) in 11 to 15 years old adolescents. Ten schools were randomly allocated to the intervention and ten schools were pair matched as controls. Fitness measures (EUROFIT battery) and self-reported sedentary behavior were collected at baseline and after 28 months. Accelerometer data were collected during five weekdays in a random subsample (n=224). The differences between intervention and control group were analyzed using mixed models considering the pair-matched design. We present tentative findings of the primary outcome measures. Results: After the intervention adolescents (n=1440) from the intervention group had less decrease in accelerometer counts (P=0.32, β=14695.9), time spent in light (P=0.46, β=1.2) and moderate to vigorous activities (P=0.17, β=9.7) and a less increases of time spent in sedentary activities (P=0.04, β=-43.8) per day than control group. In addition, they showed an improvement in shuttle-short run (P=0.03, β=-0.8), plate tapping (P=0.10, β=-0.70), sit-and-reach (P=0.37, β=0.1), sit-ups (P=0.35, β=0.1), vertical jump (P=0.01, β=2.4), bent-arm-hang (P=0.12, β=0.9) and handgrip (P=0.22, β=0.4) tests. The screen time increased in both the intervention and control group (P=0.45, β=0.07) Conclusions: A school-based intervention can moderately improve physical activity and physical fitness in adolescents. The improvement is consistent for most physical activity and fitness parameters but did not reach significance for most outcomes possibly due to a power problem with pair-matched analyses