This paper presents restraints - directly imposed restrictions on players' bodily movements, as a mechanic for bodily play in HCI. While this is a familiar mechanic in non-digital movement-based games, its potential in designing bodily play experiences in HCI has been scarcely explored. Three types of restraints observed in non-digital movement-based games, are explored here: fixating body parts, excluding body parts and depriving/manipulating bodily senses. Then, we investigate the experiential dynamics of restraints as a bodily play mechanic bridging a phenomenological perspective on bodily movement with theories on play. These investigations form the theoretical framework for the subsequent analysis of five digital body game examples. Building on this analysis and theoretical framework, we formulate five design strategies for implementing restraints as a mechanic for bodily play in HCI. We propose restraints as a generative resource for researchers and designers interested in understanding and designing bodily play experiences in HCI.