Validation of a Social Ecological Model-Based Scale for Physical Activity Among Thai Adolescents

OBJECTIVES The present study aims to validate a scale, based on the Social Ecological Model (SEM), that reflects the individual, social, and environmental determinants of physical activity among Thai adolescents. METHODS The SEM-based scale was culturally adapted for Thai adolescents through standardized translation, expert panel review, and cognitive interviewing. Data were obtained from 495 adolescents aged 12-19 years. Construct validity was examined using confirmatory factor analysis with multiple fit indices (CFI, IFI, TLI, RMSEA, SRMR), while reliability, convergent, and discriminant validity were systematically evaluated. RESULTS Among 495 Thai adolescents (mean age = 15.13 years; 54.1% male), females reported higher selfefficacy, perceived barriers, and family support. CFA supported the six-factor SEM model with good fit (CFI = 0.905, TLI = 0.900, RMSEA = 0.046). Most constructs showed adequate convergent validity (AVE ≥ 0.50, CR ≥ 0.79), while self-efficacy had lower AVE (0.40) but strong reliability (CR = 0.91, α = 0.91). Discriminant validity was confirmed. CONCLUSIONS This validated scale provides a reliable tool for Thai adolescent physical activity research in Southeast Asia, supporting evidence-based interventions and future longitudinal studies.