Psychosocial Predictors of Change in Physical Activity and Quality of Life in the PESSOA Program: A School-based Intervention Study

Background: Only 36% of 10-11 years Portuguese youngsters meet the recommendations of moderate-to-vigorous physical activity (MVPA) and they decrease progressively to 4% in the ages of 16-17 years. The aim of this study is to analyze if self-determination theory and social support variables predict change in physical activity (PA) and quality of life (QoL) in a school-based intervention study – PESSOA Program, which is a cluster randomized controlled trial that addresses mediator variables within an ecological model. Methods: Our sample was comprised of 1052 youngsters, aged 10-16 years (M=12.50 ± 1.11) allocated to control (n=207), intervention1 (n=365) and intervention2 (n=480) groups. Personal and social indicators of psychosocial health were assessed. P redictor variables were selected through hierarchical multiple regression analysis. Results: Main results were: a) increases in perceived parental and peer support accounted for the most of the PA positive changes; b) positive changes in PA were associated with increases in autonomous motivation; c) increased perceived parental and peer support, and relatedness, accounted for the most of the QoL positive changes; and, d) competence was the main predictor of positive changes in QoL. Conclusions: Our findings demonstrated that positive changes in PA and QoL were predicted through the increased perceived social support, the fulfillment of general basic psychological needs and, the endorsement of more autonomous forms of motivation toward PA.