Purpose: Grounded in self-determination theory (SDT), the present study tested how students' perceptions of autonomy support from physical education teachers predicts objectively measured moderate-to-vigorous physical activity (MVPA) of adolescents. According to SDT, it was expected that psychological needs and autonomous and controlled forms of motivation would mediate these relationships.
Methods: Students (n = 397) aged from 11 to 15 years in 17 different schools filled in questionnaires regarding SDT variables. In addition, objective MVPA was measured using an accelerometer (ActiGraph GT3X; ActiGraph, Pensacola, FL, USA) for 7 days. Structural equation modelling was used to examine the hypothesized relationships among the study variables.
Results: The theory-based model showed a good fit with the data: χ2 = 642.464, df = 257; comparative fit index = 0.932; non-normed fit index = 0.921; root mean square error of approximation = 0.062; root mean square error of approximation 90% confidence interval: 0.054-0.067. As hypothesized, there was a significant and positive direct relationship between autonomy support and need satisfaction (β = 0.81, p = 0.001). In turn, need satisfaction positively predicted intrinsic motivation (β = 0.86, p = 0.001). Intrinsic motivation was positively related to MVPA (β = 0.29, p = 0.009). A significant indirect effect (β = 0.20, p = 0.004) supported the mediating role of psychological need satisfaction and intrinsic motivation in the relationship between perceived autonomy support and objectively measured MVPA.
Conclusion: The findings of the current study support the applicability of the SDT-based model in explaining the antecedents of objectively measured MVPA of adolescents. To enhance adolescents' daily MVPA, special focus should be put on increasing their intrinsic motivation toward physical education.
Keywords: Accelerometer; Motivation; Physical activity; Physical education; Self-determination theory.
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