This article debates how muscles happen in early childhood education. Drawing on post-developmental pedagogies and feminist science studies, this article integrates moments from a pedagogical inquiry with movement in early childhood education to trace how muscles matter as complex and active ethical, political, and pedagogical concerns. After elaborating how muscles are understood in dominant Canadian pedagogical resources, I think with feminist science studies and post-developmental pedagogies to consider how muscles can be thought as an active undertaking. Then, the diaphragm muscle is mobilised to explore how physiological understandings of muscles might raise questions of muscle consequence, ongoingness, and access and activation, which extend into questions of perceptibility, process, and participation. I conclude by discussing how a focus on 'muscling' illuminates how pedagogical intentions can make muscles differently perceptible and emphasise the ethical and political complexities of doing muscling in everyday mo(ve)ments in early childhood.