Vickey and Breslin's research (published on mHealth, November 2015 issue) that involved analyzing nearly 2 million fitness tweets revealed a low percentage of mobile fitness app users meeting the recommended physical activity level. This commentary explores contextual and psychological factors that may underlie the observed low physical activity levels among these mobile fitness app users. Much remains unknown about how best to leverage technologies and social media support to promote adherence to physical activity recommendations. With the use of innovative and validated content mining strategies and taking consideration of relevant contextual and psychological factors associated with tweeting, tweets on physical activity offer a valuable data source to help us better understand: How can we mobilize people to 'tweet the walk' and 'keep the walk'?
Keywords: Twitter; mobile fitness apps; physical activity; social media.