Numerous randomised controlled trials (RCT) have examined the effectiveness of web-based physical activity interventions, and overall, these intervention studies have found to increase participants’ physical activity levels. Few studies, however, have examined how well these interventions work in ‘real world’ or ecologically valid settings, where there are no repeated contacts with research staff, comprehensive assessments or incentives. To read the full article, log in using your NHS OpenAthens details.