Changing the individual to promote health-enhancing physical activity: the difficulties of producing evidence and translating it into practice.

This paper presents conclusions from recent systematic reviews and highlights individually targeted interventions that are effective at increasing physical activity. It discusses the limitations of currently available evidence, considers what factors lead to these limitations and what barriers exist in terms of implementing the evidence as part of local and national policy and practice. Barriers present themselves in terms of getting evidence into practice and in terms of ensuring that practice informs the evidence base. These barriers include difficulties in conducting systematic reviews, disaggregating knowledge from complex interventions, making local adaptations to existing evidence, the lack of an evaluation culture, ethical and pragmatic difficulties in designing interventions, selecting appropriate outcome measures, poor designs and implementation of evidence and, finally, a recognition that policy making is not only based on the available evidence. New and more integrated approaches to evaluation and to practice are needed.