Students physical activity assessed by accelerometers and motivation for physical education during class: Should we consider lessons as a whole or only active periods?

Background: This study explores the links between measures of motivation based on Self-Determination Theory, and physical activity (PA) indicators assessed with accelerometers during physical education lessons. Methods: Questionnaires about motivation and psychological needs on the context of physical education were completed by 319 middle high school students, up to 5 times within a 2-year period; they were equipped with an accelerometer and videotaped during a physical education lesson. PA-related indicators were computed considering the entire duration of the lessons (strategy 1), but also retaining only active times during the lesson (strategy 2). Results: When the first strategy was used very few correlations emerged between motivation constructs and PA-related indicators. On the other hand, the second strategy was more effective to detect the link between motivation and students activity during class-time, in particular with sedentary time, moderate and vigorous PA. Conclusions: This study shed light on the importance of considering how the sequences of PA sessions should be coded, in order to link psychological phenomena with PA levels, as well as to provide a meaningful support for motivational hypotheses.