Effects of the 3-year Sigue la Huella intervention on sedentary time in secondary school students

Background: To examine the effects of the Sigue la Huella (Follow the Footstep) intervention on adolescents' daily sedentary time (ST). Methods: This quasi-experimental, cohort study took place in four secondary schools in Huesca (Spain) during the 2009-2010, 2010-2011 and 2011-2012 academic years (students aged 12-15 years). Two schools were assigned to the experimental condition (n = 368) and two schools to the control condition (n = 314). Sigue la Huella adopted a whole school approach and used both curricular and non-curricular intervention channels to empower students to make better decisions. ST was measured for 7 days on four occasions using accelerometers. Growth curve models were used to analyze the data. Results: In the model with all participants, a significant interaction indicated that the effect of the intervention was dependent on the study cohort considered. While in cohort 1 there were no significant differences in rate of linear change of ST between the experimental and the control group (P = 0.148), in cohorts 2 and 3 significant differences were observed in favor of the experimental group (β = -13.88, 95% CI = -25.00 to -2.76, P = 0.015; β = -76.73, 95% CI = -110.68 to -42.78, P < 0.001), independent of type of school (public vs. private) and gender. Conclusions: Sigue la Huella had mainly a protective effect in two of the three study cohorts. Whereas in cohort 2 the intervention prevented increases in ST, in cohort 3 the intervention reduced considerably the increase in ST noted in the control group.