AbstractAccording to Deci and Ryan (2002), people have psychological needs for competence, autonomy, and relatedness, and when fulfilled these needs are associated with increased well-being and behavioural persistence. Cross-sectional studies have supported this proposition, but longitudinal studies are needed to extend research. The purpose of this study was: (a) examine longitudinal measurement invariance of scores from psychological need satisfaction subscales, and (b) examine longitudinal associations between perceived competence, autonomy, and relatedness and moderate-to-vigorous physical activity (MVPA). Participants were adolescents (N = 842, Mage = 10.80 years, SD = .64) enrolled in the Monitoring Activities of Teenagers to Comprehend their Habits (MATCH) study (Bélanger et al., 2013). Self-report measures of psychological need satisfaction and MVPA were completed every 4 months over a 2-year period (2011-13). Measurement invariance analyses showed that scores from the psychological need satisfaction subscales demonstrated strong invariance (i.e., invariant factor loadings and intercepts) and partial strict invariance (i.e., invariant factor loadings and intercepts, and all but two item errors) over time. Results of the growth modeling indicated that the intercepts for perceptions of competence (r = .58), autonomy (r = .49), and relatedness (r = .45) were positively associated with initial MVPA level. Although a higher initial MVPA level was associated with a greater decline in MVPA (r = -.28), the slopes for perceptions of competence (r = 48), autonomy (r = .46), and relatedness (r = .48) were positively associated with the slope for MVPA (p < .05). Overall, invariance results provided evidence that the same constructs were measured over time, and thus methods for studying change could be applied. To this end, as psychological need satisfaction increased over 2 years, so did MVPA levels. In light of these findings, teachers, parents, and coaches should foster perceptions of psychological need satisfaction to increase MVPA in adolescents.
Acknowledgments: The MATCH project is supported by the New Brunswick Health Research Foundation (#20130729) and by the Social Sciences and Humanities Research Council and Sport Canada through the joint Sport Participation Research Initiative (#862-2010-0001).