How effective are physical activity interventions when they are scaled-up: a systematic review

The 'scale-up' of effective physical activity interventions is required if they are to yield improvements in population health. The purpose of this study was to systematically review the effectiveness of community-based physical activity interventions that have been scaled-up. We also sought to explore differences in the effect size of these interventions compared with prior evaluations of their efficacy in more controlled contexts, and describe adaptations that were made to interventions as part of the scale-up process. We performed a search of empirical research using six electronic databases, hand searched reference lists and contacted field experts. An intervention was considered 'scaled-up' if it had been intentionally delivered on a larger scale (to a greater number of participants, new populations, and/or by means of different delivery systems) than a preceding randomised control trial ('pre-scale') in which a significant intervention effect (p