title: Analyzing theoretical mechanisms of physical activity behavior change in breast cancer survivors: results from the activity promotion (ACTION) trial.
abstract: BACKGROUND
  We previously reported that a physical activity (PA) behavior change intervention based on the theory of planned behavior (TPB) increased PA and quality of life in breast cancer survivors.
  
  
  OBJECTIVE
  To examine the effects of our interventions on TPB variables and to determine if PA at 12 weeks follow-up was mediated by TPB variables at 4 weeks.
  
  
  METHODS
  Breast cancer survivors (N = 377) were randomly assigned to receive either a standard public health recommendation for PA (SR group), a step pedometer alone, or one of two TPB-based behavior change interventions consisting of print materials (alone or combined with a step pedometer). For the purpose of this study, we compared the two TPB-based intervention groups (INT group) to the SR group.
  
  
  RESULTS
  Compared to the SR group, the INT group reported more favorable changes in instrumental attitude (mean difference = 0.13; 95% CI = -0.01 to 0.23; d = 0.19; p = 0.077), intention (mean difference = 0.33; 95% CI = 0.10 to 0.56; d = 0.33; p = 0.006), and planning (mean difference = 0.39; 95% CI = 0.04 to 0.73; d = 0.26; p = 0.027). Mediation analyses indicated that both planning and intention partially mediated the effects of the intervention on PA at 12 weeks.
  
  
  CONCLUSIONS
  Our TPB-based behavior change intervention resulted in small improvements in the TPB constructs that partially mediated the effects of our intervention on PA behavior. Additional research with the TPB is warranted.
authors.affiliation: Faculty of Physical Education and Recreation, University of Alberta, E-488 Van Vliet Centre, Edmonton, AB, Canada T6G-2H9.
authors.forename: Jeffrey K H
authors.initials: JK
authors.lastname: Vallance
authors.forename: Kerry S
authors.initials: KS
authors.lastname: Courneya
authors.forename: Ronald C
authors.initials: RC
authors.lastname: Plotnikoff
authors.forename: John R
authors.initials: JR
authors.lastname: Mackey
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000416:Alberta; D001521:Behavior Therapy; D001823:Body Composition; D001943:Breast Neoplasms / Q000473:pathology / Q000523:psychology / Q000534:rehabilitation*; D003131:Combined Modality Therapy; D003469:Culture; D015444:Exercise / Q000523:psychology*; D005260:Female; D005500:Follow-Up Studies; D007722:Health Knowledge, Attitudes, Practice; D006293:Health Promotion / Q000379:methods*; D006801:Humans; D033182:Intention; D008875:Middle Aged; D009042:Motivation; D009367:Neoplasm Staging; D010174:Pamphlets; D010353:Patient Education as Topic; D011446:Prospective Studies; D011788:Quality of Life / Q000523:psychology; D011795:Surveys and Questionnaires