The design space of social exergames remains narrow despite the many benefits of playing and exercising together. Towards opening this design space, we followed a Research through Design (RtD) approach focused on exergames that can be fun and immersive social training experiences. Through embodied sketching activities with designers and 10 pairs of players, we explored future games for the ExerCube, an immersive exergame platform. Our work contributes with forms of intermediate-level knowledge: a design space model (the Immersive Social Fitness—ImSoFit—Games model); and a novel design vocabulary including new bodily orientations in co-located physical interaction. We illustrate their use and value scrutinizing three of our games and applying three analytical lenses to 1) understand how design choices impact how players move together; 2) evaluate design expectations and analyze players’ behavior in relation to design choices; and 3) potentially extend the design space of immersive co-located social fitness games.