A Longitudinal Evaluation of an Intervention Program for Physical Education Teachers to Promote Adolescent Motivation and Physical Activity in Leisure Time: A Study Protocol

(1) Background: Research has consistently demonstrated that regular physical activity (PA) is associated with several benefits among adolescents. However, PA levels among adolescents are low worldwide and tend to decrease with age. Consequently, researchers aim to identify psychological antecedents of PA to inform effective interventions, including in physical education (PE) settings. PE lessons provide an ideal environment for conveying health-related messages to adolescents. (2) Methods: This project aims to develop a three-month face-to-face and web-based intervention program for PE teachers to increase autonomy-, competence-, and relatedness-supportive behavior toward their students (main trial phase 1: min <i>n</i> = 78; main trial phase 2: min <i>n</i> = 116) and to avoid the respective need-thwarting behaviors toward their students. The effectiveness of the intervention program is examined at multiple time points during the three-month period. (3) Results: After the intervention program, it is expected that the experimental group students demonstrate significantly higher intrinsic motivation toward PA and are significantly more physically active, as measured by accelerometers, compared to control group students. Additionally, the unique effects of autonomy, competence, and relatedness support interventions on students' intrinsic motivation and PA will be investigated. (4) Conclusions: This project provides highly valuable insights for PE teacher training to increase students' intrinsic motivation and their overall PA.