title: Mediators of physical activity behavior change: findings from a 12-month randomized controlled trial.
abstract: OBJECTIVE
  To examine putative mediators of a 12-month motivationally tailored physical activity (PA) promotion intervention.
  
  
  METHODS
  We randomly assigned 239 healthy, underactive adults (moderate-vigorous physical activity <90 min/week; mean age = 47.5 years; 82% women) to receive (a) print-based feedback, (b) phone-based feedback, or (c) contact control.
  
  
  METHODS
  PA at baseline, 6, and 12 months, as measured by the 7-day physical activity recall interview. MEDIATORS: Four TransTheoretical Model constructs explicitly targeted by the intervention (i.e., self-efficacy, decisional balance, cognitive and behavioral processes of change), as well as four additional constructs linked to PA behavior change (i.e., social support, outcome expectancy, PA enjoyment, exercise-induced feelings).
  
  
  RESULTS
  Multivariate mediation analyses were used to analyze longitudinal PA outcomes. Changes in behavioral processes and one aspect of exercise-induced feelings (revitalization) satisfied both action theory (i.e., treatment effects on mediators) and conceptual theory (i.e., mediator effects on PA) tests at 6 and 12 months and emerged as statistically significant mediators of treatment effects on PA across delivery channels (ps <.014). Cognitive processes, self-efficacy, decisional balance, and social support for PA participation satisfied Action Theory tests at both 6 and 12 months, but failed conceptual theory tests. Delayed intervention effects were observed on other aspects of exercise-induced feelings, PA enjoyment, and outcome expectancies, but these variables failed mediation testing at 12 months.
  
  
  CONCLUSIONS
  Findings are consistent with previous research illustrating the importance of behavioral processes of change, but also indicate that affective response to PA may warrant more attention as a potential target of behavior change programs.
authors.affiliation: Department of Biostatistics, Brown University, Providence, RI 02912, USA. gdp@stat.brown.edu
authors.forename: George D
authors.initials: GD
authors.lastname: Papandonatos
authors.forename: David M
authors.initials: DM
authors.lastname: Williams
authors.forename: Ernestine G
authors.initials: EG
authors.lastname: Jennings
authors.forename: Melissa A
authors.initials: MA
authors.lastname: Napolitano
authors.forename: Beth C
authors.initials: BC
authors.lastname: Bock
authors.forename: Shira
authors.initials: S
authors.lastname: Dunsiger
authors.forename: Bess H
authors.initials: BH
authors.lastname: Marcus
mesh_terms: D000328:Adult; D003071:Cognition; D015444:Exercise / Q000523:psychology*; D005246:Feedback; D005260:Female; D015438:Health Behavior; D006293:Health Promotion / Q000379:methods; D006801:Humans; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D009042:Motivation; D020377:Self Efficacy; D012944:Social Support