As digital tracking technologies such as heart rate monitors are being implemented into physical education classrooms with increased frequency, 'techno-enthusiasts' and 'sceptics' alike are attempting to understand the implications of these practices. Focusing on heart rate monitors in physical education, I utilize Foucauldian theories and actor-network-theory to extend the scholarship within the sociology of sport and physical education literature that has studied the relationship between technologies and the (in)active body. To better understand how the feedback loop of heart rate monitoring functions in the university-level physical education class that was studied here--or indeed, does not function--I consider the material-semiotic networks that variously form or fail to form alliances through the feedback loop of heart rate monitoring. These include the numerous technologies and bodies that are a part of this assemblage, an interest in heart rate data, and knowledge about heart rate. I conclude by arguing that we need to move beyond the techno-utopian/techno-dystopian dualism that often frames examinations of technology in PE.