Emerging research explores the role of self-tracking in supporting healthy behaviour. Self-tracking comprises a number of interrelated practices; some individual some communal. In this paper we focus on practices that enable interaction between self-trackers through data sharing and communication around personal data. For public health, communal self-tracking has been explored for the additional benefits it provides in addition to self-knowledge. However, under-explored is the emotional entanglement of self-tracking and tracked activities, or the role of practitioners in the dynamic evolution of tracked practices. Qualitative, mixed methods data was collected from leisure-time runners in the SW England who self-track using social fitness app ‘Strava’, and was interpreted through the lens of practice theory. We find that communal self-tracking affords the active shaping of the emotion and purpose of running. This ‘teleoaffective shaping’ allows practitioners to negotiate and reconstitute appealing meanings associated with running to protect their practice loyalty. We identify three mechanisms for teleoaffective shaping afforded by Strava: labelling, reward and materialising effort. Findings advance our understanding of how social fitness apps work to retain practitioners of physically active leisure practices. Future research should further explore the multiple ways that associations with tracked physical activity evolve through entanglement with self-tracking practices.