Investigating motivational regulations and physical activity over 25 weeks

Background: Because motivation has been deemed a key barrier to physical activity, it is imperative that we know how motivational levels change over time and how that change relates to physical activity. Based in Self-Determination Theory, this study investigated fluctuations in physical activity and motivational regulations over 25 weeks and tested the relationship between these 2 variables. Methods: Data from the Physical Activity Counseling trial were examined. Inactive adults recruited from a primary care center (N = 120) answered motivation and physical activity questionnaires during the intervention and postintervention phases. Hierarchical linear modeling was used to test the hypotheses. Results: Quadratic changes were found for external regulation (γ₂₀= 0.02, P < .05) and physical activity (γ₂₀= -2.64, P < .001), while identified (γ₁₀= 0.04, P = .03) and intrinsic (γ₁₀= 0.04, P = .01) regulations increased linearly over the course of the 25 weeks. Only identified regulation (γ₃₀= 3.15, P = .01) and intrinsic motivation (γ₃₀= 4.68, P < .001) were significantly and positively related with physical activity. Conclusion: Physical activity, external and identified regulations and intrinsic motivation changed over the 25 weeks. Intervention should aim at fostering identified regulation and intrinsic motivation as greater levels of these regulations were related with physical activity.