Mobile fitness applications (a.k.a. “apps”) are widely used to manage personal health records. The success of fitness apps hinges on their ability in promoting users’ exercise activities. The gamified design element has been widely employed by fitness apps as an effective approach to motivate users to exercise more. However, the efficacy of different gamified elements in influencing users’ subsequent exercise behaviors is still under debate in both research and practice. In this research-in-progress paper, we anchor the social comparison mechanisms to accordingly design gamification elements and demonstrate the dual impact of gamification on users’ exercise behavior change. In addition, we argue that the improvement of users’ exercise performance hinges on the extent to which users’ dispositional approach avoidance temperament is aligned with user’ gamification-enabled social comparison motives. The theoretical inference will guide a future field experiment by testing the effect of gamification on the users’ exercise performance change.