title: Understanding for whom, under what conditions, and how group-based physical activity interventions are successful: a realist review.
abstract: BACKGROUND
  Participation in group-based physical activity (GBPA) interventions has been found to result in higher levels of exercise adherence and program compliance. However, previous reviews of GBPA programs have provided limited insight regarding 'for whom', 'under what conditions', and 'how' these interventions increase physical activity behavior.
  
  
  METHODS
  A realist review was conducted by following the seven recommended iterative and overlapping steps (J Health Serv Res Policy 10S1:21-34, 2005). The review was limited to group dynamics-based interventions for adults (>17 years of age). The search was conducted in PubMed, PsychInfo, and Web of Science search engines associated with the Science Citation Index Expanded, Social Sciences Citation Index, Arts & Humanities Citation Index, and MEDLINE.
  
  
  RESULTS
  Using a realist review approach, data from 52 studies were synthesized. Of those, 92% (n = 48) reported significant increases in participant physical activity. The synthesis resulted in three main observations and recommendations.
  
  
  CONCLUSIONS
  GBPA interventions have worked for a variety of populations, including those who are hard to reach; however, more research is needed on moderating factors to determine for whom different GBPA programs may be effective. Second, previous interventions have varied in the duration, frequency, and number of group-based strategies used, and comparative effectiveness research may be necessary to isolate the mechanisms of effect. Third, these interventions have been conducted in a diverse range of settings, using a variety of research designs and analytical approaches. Less information is known about the costs or sustainability of these programs in their intended settings.
  
  
  CONCLUSIONS
  The results of this realist review have important implications for practice, refining trial designs, and replication across diverse populations and settings.
authors.affiliation: Human Nutrition, Foods and Exercise, Virginia Tech, 1981 Kraft Dr., Room 1009, Blacksburg, VA, 24060, USA. harden.samantha@vt.edu.|University of British Columbia, School of Kinesiology, 6081 University Blvd, Vancouver, BC, V6T 1Z1, USA. harden.samantha@vt.edu.
authors.forename: Samantha M
authors.initials: SM
authors.lastname: Harden
authors.affiliation: University of British Columbia, School of Kinesiology, 6081 University Blvd, Vancouver, BC, V6T 1Z1, USA. desi.mcewan@gmail.com.
authors.forename: Desmond
authors.initials: D
authors.lastname: McEwan
authors.affiliation: University of British Columbia, School of Kinesiology, 6081 University Blvd, Vancouver, BC, V6T 1Z1, USA. bsylvest@alumni.ubc.ca.
authors.forename: Benjamin D
authors.initials: BD
authors.lastname: Sylvester
authors.affiliation: University of British Columbia, School of Kinesiology, 6081 University Blvd, Vancouver, BC, V6T 1Z1, USA. megankaulius@gmail.com.
authors.forename: Megan
authors.initials: M
authors.lastname: Kaulius
authors.affiliation: University of British Columbia, School of Kinesiology, 6081 University Blvd, Vancouver, BC, V6T 1Z1, USA. geri.ruissen@gmail.com.
authors.forename: Geralyn
authors.initials: G
authors.lastname: Ruissen
authors.affiliation: School of Health Studies, Western University, 1151 Richmond St, Room 216, HSB, London, ON, N6A 3 K7, USA. sburke9@uwo.ca.
authors.forename: Shauna M
authors.initials: SM
authors.lastname: Burke
authors.affiliation: Human Nutrition, Foods and Exercise, Virginia Tech, Family and Community Medicine, Carilion Clinic, 1 Riverside Circle, Roanoke, VA, 24016, USA. estabrkp@vt.edu.
authors.forename: Paul A
authors.initials: PA
authors.lastname: Estabrooks
authors.affiliation: University of British Columbia, School of Kinesiology, 6081 University Blvd, Vancouver, BC, V6T 1Z1, USA. mark.beauchamp@ubc.ca.
authors.forename: Mark R
authors.initials: MR
authors.lastname: Beauchamp
mesh_terms: D000328:Adult; D005081:Exercise Therapy / Q000379:methods*; D005260:Female; D006127:Group Structure; D006801:Humans; D008297:Male; D015397:Program Evaluation / Q000379:methods*