The effect of an intervention on physical activity of moderate-and-vigorous intensity, and sedentary behavior during adolescents' time at school.

INTRODUCTION

This study evaluated the effect of an intervention on the engagement in physical activity (PA) and sedentary behavior (SB) of sixth to ninth grade students during school-time, physical education (PE) classes, and recesses at two public schools in Florianopolis, SC, Brazil.

METHOD

Schools were divided into control and experimental groups. Participants wore accelerometers during school-time, and PA and SB were estimated for school-time, PE classes and recesses at the baseline and after the intervention. The intervention was composed of four components: changes were made in the PE classes, including giving instruction to teachers; sports equipment was made available for use during recesses; educational sessions on the format of classes were conducted; folders and posters were distributed. Data was analyzed using an Analysis of Covariance for repeated measures comparing baseline data with post intervention data, and for independent samples when comparing control and intervention groups.

RESULTS

A low proportion of engagement in PA and a large engagement in SB was observed on the baseline. PA decreased in the intervention group during PE classes, while it increased in the control group with regard to school-time, PE classes, and recess. The intervention group accumulated more SB during school-time and PE classes after the intervention, while a decrease in the control group's SB during school-time was observed.

CONCLUSION

The intervention was not effective in increasing PA or decreasing SB. Environmental and school's organizational factors impact how interventions are conducted, and should be considered beforehand.