Drawing on data generated by a two-year ethnographic study in a high security Spanish prison, this article explores the multiple meanings given to the social practices of sport and physical activity. We provide details of the following key themes that emerged from the analysis: (a) escaping time; (b) perceived therapeutic benefits; (c) social control; (d) gendered dimensions; and (e) performing masculinity. The findings suggest that a diverse and contradictory set of meanings are associated with sport and physical activity within this particular prison culture, and that the performance of specific kinds of masculinity is both a process and product that shapes the construction of experience in powerful ways. (Contains 2 notes.)