title: Testing social-cognitive theory to explain physical activity change in adolescent girls from low-income communities.
abstract: OBJECTIVE
  The aim of this study was to test the hypothesized structural paths in Bandura's social-cognitive theory (SCT) model on adolescent girls' physical activity following a 12-month physical activity and dietary intervention to prevent obesity.
  
  
  METHODS
  We conducted a 12-month follow-up study of 235 adolescent girls (M(age) = 13.2 years, SD = 0.4) from 12 secondary schools located in low-income communities. At baseline, participants completed SCT scales related to physical activity (i.e., self-efficacy, intention, parental support, and outcome expectations). At baseline and 12-month follow-up (postintervention), participants wore accelerometers for 7 days. Structural equation modeling was used to determine if Time 1 measures predicted physical activity at 12-month follow-up after adjusting for baseline activity.
  
  
  RESULTS
  The model explained 28% and 34% of the variance in physical activity and intention, respectively. Model fit indexes indicated the data were a good fit to the model; however, only self-efficacy was associated with physical activity at 12 months. There was no support for intention or outcome expectations as proximal determinants of behavior. Self-efficacy was associated with outcome expectations and parental support; however, only outcome expectations predicted intention.
  
  
  CONCLUSIONS
  Current findings indicate a large proportion of the variance for physical activity and intention remains unexplained and that the proposed pathways in the SCT model were not fully supported. Future model testing may need to consider augmentation or integration of theoretical models, which may include ecological components if we are to advance our understanding of physical activity behavior in this subgroup of the adolescent population.
authors.affiliation: University of Newcastle at Callaghan, Australia.
authors.forename: Deborah L
authors.initials: DL
authors.lastname: Dewar
authors.affiliation: University of Newcastle at Callaghan, Australia.
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Plotnikoff
authors.affiliation: University of Newcastle at Callaghan, Australia.
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Morgan
authors.affiliation: University of Wollongong, Australia.
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Okely
authors.affiliation: University of Newcastle at Callaghan, Australia.
authors.forename: Sarah A
authors.initials: SA
authors.lastname: Costigan
authors.affiliation: Priority Research Centre in Physical Activity and Nutrition, University of Newcastle at Callaghan, ATC Rm. 301C, Health and Physical Education Building, University Drive, Newcastle, NSW 2308, Australia.
authors.forename: David R
authors.initials: DR
authors.lastname: Lubans
mesh_terms: D061725:Accelerometry / Q000295:instrumentation; D000293:Adolescent; D000294:Adolescent Behavior / Q000523:psychology*; D005260:Female; D005500:Follow-Up Studies; D015438:Health Behavior; D006293:Health Promotion; D006801:Humans; D009043:Motor Activity; D009765:Obesity / Q000517:prevention & control; D011204:Poverty Areas; D011582:Psychological Theory; D020377:Self Efficacy