Technology supporting motivation for physical activity has been a common theme for researchers and companies during the last decade. Mobile devices and applications with diverse features provide novel and personalized ways to motivate users for healthier lifestyles. Features like goal orientation and self-monitoring are common for activity and emotion tracking applications, and lately there has been interest also in the use of narratives. Consequently, in this study we evaluate through a qualitative study how narratives are used to motivate physical activity. We analyze both user and system-specific characteristics using nexus analysis and conclude with three techniques for personalizing narratives.