Despite various benefits of physical activity, children are increasingly inactive. Both school physical education classes and support from parents are important determinants of physical activity level of children and adolescents. We aim to develop a web-based intervention for physical education teachers and parents to teach them to be more need-supportive towards children when discussing physical activity and thus increase children's autonomous motivation towards it. The study will adopt a waitlist-control design with cluster randomization by schools. The intervention content is based on self-determination theory. Specifically, the teachers and parents will be introduced to a series of motivation and behavior change techniques to help them satisfy the children's psychological needs for autonomy, competence, and relatedness in physical activity. The targeted group in the six-week intervention is comprised of students aged 12-14 years. The primary outcome variable, physical activity of students, will be assessed via self-report questionnaires at baseline, post-intervention, one-month and six-month follow-up. Web-based intervention programs are cost-effective, allow self-paced learning and enable reaching larger audiences. If this project proves to be effective, a highly valuable web-based solution would be available for PE teachers and parents to help increase students' physical activity levels.
Keywords: adolescents; autonomy; children; competence; motivation; relatedness; self-determination theory; theory of planned behavior; trans-contextual model of motivation.