Viral buzz on social network sites about physical activity: fad or fabulous?

While there is a growing trend to use social media for public health promotion, research on its actual potential to influence health behaviors is limited. This dissertation explores whether and how social network sites (SNSs) can be used to promote physical activity (PA) through electronic word of mouth (eWOM). Composed of two studies, this dissertation explores PA-related eWOM from both the senders' and receivers' perspectives, and examines actual messages. The first study uses a web survey and explores the antecedents and communication consequences of eWOM about leisure-time PA (LTPA), and the behavioral consequences of eWOM among college students. The second study is based on a content analysis of public Twitter posts in the U.S. in 2011 regarding PA. Based on Sun et al.'s (2006) Path Model of Antecedents and Consequences of Online Word of Mouth, it was found that undergraduate SNS users with higher affective involvement and stronger social ties with their SNS contacts were more likely to provide opinions or information about PA. People with stronger social ties were also more likely to seek opinions or information. Both opinion leadership and opinion seeking were associated with forwarding and chatting. Applying the Theory of Planned Behavior, the first study also found social support of PA via eWOM on SNSs is associated with both affective and instrumental attitudes, subjective norms, and perceived behavioral control (PBC), while social negativity of PA via eWOM on SNSs is associated with instrumental attitudes and PBC. Affective attitude, instrumental attitude, and PBC, in turn, predict intention to participate in LTPA. Moreover, when putting all these different constructs together to predict intention, social support via eWOM was found to indirectly influence the intention to participate in LTPA through the constructs in the Theory of Planned Behavior (including affective and instrumental attitudes and perceived behavioral control). Applying the components of both the Path Model of Antecedents and Consequences of Online Word of Mouth and the Social Cognitive Theory, the second study examined Twitter posts of PA-related eWOM. PA modeling dominated the different aspects of social influence. Most people chat rather than forward information, and provide rather than seek opinions and information about PA. PA type is associated with PA modeling in multiple ways. People with more followers are more likely to forward information about PA. This dissertation widens and deepens the understanding of PA-related eWOM on SNSs by the application of theoretical frameworks from both marketing and health behavior fields. The results suggest that people who find PA interesting and fun, perceive themselves as close to their contacts on SNSs, and have larger social network on SNSs can be recruited as opinion leaders in future interventions to promote PA. These opinion leaders can provide PA modeling and social support though SNSs which will increase their contacts' positive attitudes and PBC and consequently increase their intention to participate in PA.