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BACKGROUND: Developing Web-based physical activity (PA) interventions based on motivational interviewing (MI) could increase the availability and reach of MI techniques for PA promotion. Integrating an avatar in such an intervention could lead to more positive appreciation and higher efficacy of the intervention, compared to an intervention that is purely text-based. OBJECTIVE: The present study aims to determine whether a Web-based PA intervention based on MI with an avatar results in more positive appreciation and higher effectiveness of the intervention, when compared to an intervention that is purely text-based. METHODS: A three-arm randomized controlled trial was conducted, containing the following research conditions: (1) a Web-based PA intervention based on MI with an avatar, (2) a content-identical intervention without an avatar, and (3) a control condition that received no intervention. Measurements included PA behavior and process variables, measured at baseline, directly following the intervention and 1 month post intervention. RESULTS: Both interventions significantly increased self-reported PA at 1 month, compared to the control condition (beta(AVATARvsCONTROL)=.39, P=.011; beta(TEXTvsCONTROL)=.44, P=.006). No distinctions were found regarding intervention effect on PA between both interventions. Similarly, the results of the process evaluation did not indicate any significant differences between both interventions. Due to the limited relational skills of the avatar in this study, it probably did not succeed in forming a stronger relationship with the user, over and above text alone. CONCLUSIONS: The findings suggest that avatars that do not strengthen the social relationship with the user do not enhance the intervention impact. Future research should determine whether Web-based PA interventions based on MI could benefit from inclusion of a virtual coach capable of more complex relational skills than used in the current study, such as responding in gesture to the user's state and input. TRIAL REGISTRATION: Dutch Trial Register trial number: NTR3147; http://www.trialregister.nl/trialreg/admin/rctview.asp?TC=3147 (Archived by WebCite at http://www.webcitation.org/6NCbwdUJX).
Friederichs et al. (Thu,) studied this question.