Over the last decade, cable-driven parallel mechanisms have been used for several purposes. In this paper, a novel application is proposed, namely, using two 6-DOF cable-driven parallel mechanisms sharing a common workspace to obtain the mechanical base for the design of a locomotion interface. The methodology used to develop the architecture of the mechanisms is presented and the two main criteria used to optimize the geometry are described. These criteria are based on the Wrench-Closure Workspace (WCW) and a detection of the mechanical interferences between all the entities of the locomotion interface (cables and moving bodies). Then, the final design is described and its performances are given. Finally, in order to validate the relevance of the mechanism for the locomotion interface’s design, tensile forces in the cables are computed to observe maximal values reached during a typical human gait trajectory.