Predicting Adolescents' Leisure-Time Physical Activity Levels: A Three-Wave Prospective Test of the Integrated Model of Self-Determination Theory and the Theory of Planned Behavior.

A three-wave prospective study was conducted to provide a better understanding of the ability of the integrated model of self-determination theory (SDT) and the theory of planned behavior (TPB) to predict future physical activity (PA) engagement among adolescents. Nearly 2500 secondary school students from China were recruited to test the hypothesized pathway from autonomous motivation from SDT at baseline (T1) through the constructs of TPB one month later (T2) on leisure-time PA levels of secondary school students three months later (T3). The findings revealed that the structural equation models yielded excellent fit indices with χ = 1858.989, = 257, CFI = 0.936, TLI = 0.926, RMSEA = 0.050 [90% CI = 0.048 to 0.052], and SRMR = 0.032. In particular, autonomous motivation at T1 was positively associated with attitude (R = 0.160), subjective norms (R = 0.160), and perceived behavioral control (PBC) (R = 0.173) at T2 ( = 0.395 to 0.414, < 0.001) and subsequently associated with intention at T2 (R = 0.875, = 0.112 to 0.478, < 0.001). T2 intention was positively associated with leisure-time PA levels (R = 0.004) at T3. Our findings contribute to a better understanding of the motivational mechanisms and social cognition processes involved in predicting adolescents' leisure-time PA levels among adolescents.