title: Context effects and behaviour change techniques in randomised trials: a systematic review using the example of trials to increase adherence to physical activity in musculoskeletal pain.
abstract: OBJECTIVE
  To describe and explore the effects of contextual and behaviour change technique (BCT) content of control and target interventions in clinical trials.
  
  
  METHODS
  Review and meta-analysis of 42 trials from a Cochrane review of physical activity in chronic musculoskeletal pain.
  
  
  METHODS
  Two researchers coded descriptions of target and control interventions for (a) 93 BCTs and (b) whether target and control interventions shared each of five contextual features (practitioners' characteristics, patient-practitioner relationship, intervention credibility, superficial treatment characteristics e.g. delivery modality, and environment). Quality of study reporting was assessed. Effect sizes for adherence to physical activity and class attendance were computed (Cohen's d) and analysed separately.
  
  
  RESULTS
  For physical activity outcomes, after controlling for reporting quality, larger effect sizes were associated with target and control interventions using different modalities (β = -.34, p = .030), target and control interventions involving equivalent patient-practitioner relationship (β = .40, p = .002), and target interventions having more unique BCTs (i.e. more BCTs not also in the control) (β = .008, p = .030). There were no significant effect moderators for class attendance outcomes.
  
  
  CONCLUSIONS
  Contents of control conditions can influence effect sizes and should be considered carefully in trial design and systematic reviews.
authors.affiliation: a Faculty of Social and Human Sciences, Centre for Applications of Health Psychology , University of Southampton , Southampton , UK.
authors.forename: Felicity L
authors.initials: FL
authors.lastname: Bishop
authors.forename: Anya L
authors.initials: AL
authors.lastname: Fenge-Davies
authors.forename: Sarah
authors.initials: S
authors.lastname: Kirby
authors.forename: Adam W A
authors.initials: AW
authors.lastname: Geraghty
mesh_terms: D001521:Behavior Therapy; D006801:Humans; D009043:Motor Activity; D059352:Musculoskeletal Pain / Q000523:psychology* / Q000628:therapy; D010349:Patient Compliance / Q000523:psychology* / Q000706:statistics & numerical data; D016032:Randomized Controlled Trials as Topic / Q000379:methods*
keywords: behaviour change techniques; control groups; methodology; physical activity; placebo effects; trial design