Exploring the impact of the 'new' ParticipACTION: overview and introduction of the special issue.

ParticipACTION is the Canadian physical activity communications and social marketing organization first launched in the fall of 1971 and then ceased operations in 2001. ParticipACTION was relaunched in 2007. Framed as a public health natural experiment, evidence was collected from a population-based survey of knowledge, awareness, understanding of physical activity, and physical activity levels among Canadians (individual level), and key informant surveys and interviews examining capacity, readiness and advocacy for physical activity promotion among physical activity organizations (organizational level). The purpose of this paper is to first provide an overview of some of the major initiatives undertaken by the 'new' ParticipACTION that may have contributed to any changes at these individual or organizational levels. Second, the paper sets the stage for the three empirical papers in this special series reporting follow-up results.