title: How big is the physical activity intention-behaviour gap? A meta-analysis using the action control framework.
abstract: OBJECTIVE
  The physical activity (PA) intention-behaviour gap is a topic of considerable contemporary research, given that most of our models used to understand physical activity suggest that intention is the proximal antecedent of behavioural enactment. The purpose of this study was to quantify the intention-PA gap at public health guidelines with a meta-analysis of the action control framework.
  
  
  METHODS
  Systematic review and meta-analysis.
  
  
  METHODS
  Literature searches were conducted in July 2012 among five key search engines. This search yielded a total of 2,865 potentially relevant records; of these, 10 studies fulfilled the full eligibility criteria (N = 3,899).
  
  
  RESULTS
  Random-effects meta-analysis procedures with correction for sampling bias were employed in the analysis for estimates of non-intenders who subsequently did not engage in physical activity (21%), non-intenders who subsequently performed physical activity (2%), intenders who were not successful at following through with their PA (36%), and successful intenders (42%). The overall intention-PA gap was 46%.
  
  
  CONCLUSIONS
  These results emphasize the weakness in early intention models for understanding PA and suggest this would be a problem during intervention. Contemporary research that is validating and exploring additional constructs (e.g., self-regulation, automaticity) that augment intention or improving the measurement of motivation seems warranted.
  What is already known on this subject? Intention is considered the proximal antecedent of behaviour in many popular models. Intention is also an established correlate of physical activity behaviour, yet discordance is considerable in experimental research. What does this study add? This meta-analysis of studies that have assessed concordance/discordance of physical activity intention and behaviour at public health guidelines shows the intention-behaviour gap at 48% and the discordance is from intenders who do not act. The results demonstrate that discordance is not just from extreme levels of intention or behaviour (e.g., intend to exercise six times but only exercise five), but from levels that are relevant to health promotion.
authors.affiliation: Behavioural Medicine Laboratory, University of Victoria, Victoria, British Columbia, Canada. rhodes@uvic.ca
authors.forename: Ryan E
authors.initials: RE
authors.lastname: Rhodes
authors.forename: Gert-Jan
authors.initials: GJ
authors.lastname: de Bruijn
mesh_terms: D001294:Attitude to Health; D015444:Exercise / Q000523:psychology*; D015438:Health Behavior; D006801:Humans; D033182:Intention