A tale of two models: changes in psychological need satisfaction and physical activity over 3 years

Abstract

Abstract: Objective: (a) Examine longitudinal measurement invariance of scores from psychological need satisfaction (PNS) scales and (b) examine if changes in PNS were associated with change in moderate-to-vigorous physical activity (MVPA). Methods: Adolescents (N=842, Mage = 10.8, SD = .6) enrolled in the Monitoring Activities of Teenagers to Comprehend their Habits (MATCH) study completed measures of PNS and MVPA every 4 months over a 3 year period (2011-14) for a total of nine times. Results: PNS scores demonstrated strong longitudinal measurement invariance (i.e., invariant factor loadings and intercepts). Latent growth curve modeling indicated that a factor representing perceptions of all three PNS variables was positively associated with MVPA at Time 1 (β = .566, p<.05), and that increases in the common PNS factor were associated with increases in MVPA (β = .545, p<.05) with a large effect size (R2initial MVPA=.316; R2change in MVPA=.301). In an alternative model, MVPA at Time 1 was associated with perceived common PNS at Time 1 (β=.602, p<.001), and increases in MVPA were associated with increases in common PNS (β=.667, p<.001) with a large effect size (R2initial PNS=.363 of the R2change in PNS=.426). Conclusions: Longitudinal measurement invariance was supported, and therefore PNS scores could be used to study change over time. Further, two equally well fitting models were found suggesting that change in PNS can be both an antecedent and an outcome of MVPA. As such, both PNS and MVPA could be targeted in interventions aimed at increasing need satisfaction or MVPA.