Longitudinal study of physical activity in college students: Testing self-determination theory based on stages of change

The main purpose of this study was to longitudinally test the relationships of Self Determination Theory variables on physical activity, analyzing the model based on stages of change. The study is a longitudinal and quantitative research. We have developed a longitudinal cross-lagged design for structural equation models of three time points and multi-group analysis. Participants were 772 Spanish college students from the University of Zaragoza (M = 19.74, SD = 2.76) studying several degrees. Participants completed different self-reports, assessing: physical activity, stages of change, motivation and basic psychological needs, at three time points (November, January and March). The analysis indicated that intrinsic motivation positively predicted physical activity at the 3-time points, both directly and indirectly. Intrinsic motivation was negatively predicted by autonomy and positively predicted by competence (from time point 2 to 3). No relationships were found with relatedness for the entire sample. Regarding the stages of change multi-group analysis were run: in the low active group, we found a negative relationship between relatedness and physical activity, and a positive association between competence and intrinsic motivation and physical activity, whereas intrinsic motivation did not predict physical activity. Our findings showed that intrinsic motivation was the most consistent predictor of physical activity. The competence need played an essential role in intrinsic motivation and physical activity for both active and passive subjects. However, the basic psychological needs have not worked as indicated by the theory when it was examined longitudinally. The findings of the study highlight the need for different strategies to improve physical activity levels according to the stages of change.