This article investigates how particular conceptions of physical development (PD) are enacted in early childhood studies in Toronto, Canada. Following critical childhood studies scholars who emphasize the urgency of re-formulating relationships with taken-for-granted concepts in the field, we argue for a practice of noticing, tracing, naming, and questioning how PD comes to matter as a strategy toward becoming accountable for the ethical and political consequences of how we use, teach, and critique PD. We trace three formations of PD relevant to Toronto: (1) PD informed by bioscientific knowledges; (2) PD as synonymous with physical literacy and (3) PD as a distinct mode of learning. With each conceptualization, we interrogate how PD is produced as a concept worthy of concern, take seriously the possibilities for children's learning and lives enabled by each understanding, and then draw upon interdisciplinary perspectives to complexify how we might 'do' PD otherwise. We conclude by offering our practice of tracing, interrogating, and doing PD as an ongoing commitment, whereby scholars, students, and practitioners might continually re-visit how and why we come to understand PD with particular relations, knowledges, resources, and intentions.