Beauchamp, Mark R.Harden, Samantha M.Wolf, Svenja A.Rhodes, Ryan E.Liu, YanDunlop, William L.Schmader, ToniSheel, Andrew W.Zumbo, Bruno D.Estabrooks, Paul A.2015-09-142015-09-1420152015-06-27Beauchamp et al.: GrOup based physical Activity for oLder adults (GOAL) randomized controlled trial: study protocol. BMC Public Health (2015) 15:592http://dx.doi.org/10.1186/s12889-015-1909-9http://www.biomedcentral.com/1471-2458/15/592http://hdl.handle.net/1828/6694BioMed CentralBackground: Physical activity has health benefits across the lifespan, yet only 13 % of Canadian older adults are sufficiently active. Results from a number of observational studies indicate that adults display positive preferences for exercising with others of a similar age and same gender, and that intra-group age- and gender-similarity are associated with elevated exercise adherence. However, research has yet to experimentally examine the extent to which intra-group age- and gender-related similarity affect exercise adherence behaviors. Methods/design: The GrOup-based physical Activity for oLder adults (GOAL) trial is a three-arm randomized control trial that will examine the efficacy of two different group-based exercise programs for older adults (informed by the tenets of self-categorization theory) in relation to a standard group-based exercise program. Within this manuscript we outline the design and proposed evaluation of the GOAL trial. The first arm is comprised of exercise groups made up of participants of a similar-age and of the same gender; the second arm consists of groups with similar-aged mixed gender participants; the control arm is comprised of mixed-aged mixed gender participants. We aim to compare the adherence rates of participants across conditions, as well as potential moderation effects and mediating mechanisms. Discussion: Results from this trial will inform intervention designs to improve the exercise adherence behaviors of older adult. At a systems-level, should support be derived for the efficacy of the interventions tested in this trial, changing group composition (i.e., age, gender) represents a feasible program adaptation for physical activity centers. Trial registration: ClinicalTrials.gov # NCT02023632. Registered December 13, 2013.enAttribution-NonCommercial-NoDerivs 2.5 CanadaPhysical activityOlder adultsAdherenceSelf-categorization theoryGroup-dynamicsBehavioural Medicine LabArticleSchool of Exercise Science, Physical and Health Education