Empowering adolescents to be physically active: three-year results of the Sigue la Huella intervention.

Objective: To examine the effects of a school-based intervention called Sigue la Huella (Follow the Footstep) on adolescents' daily moderate-to-vigorous physical activity (MVPA).

Method: 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 was based on the social ecological model and self-determination theory. MVPA was measured for 7 days on 4 occasions using accelerometers. Data were analyzed with individual growth curve models.

Results: There was a significant difference in linear growth rate of daily MVPA between the experimental and the control group, independent of study wave, type of school (public vs. private), grade level and gender (p<0.001). Specifically, MVPA increased in the experimental group (β=7.02, 95% confidence interval (CI)=1.27 to 12.78, p=0.017) and tended to decrease in the control group (β=-5.26, 95% CI=-11.17 to 0.65, p<0.081). The observed increase was larger in boys than in girls (p=0.003).

Conclusions: Sigue la Huella had a positive effect on adolescents' daily MVPA over three school years. Both genders benefited from the intervention, although boys to a greater extent.