Apparatus for bi-directional ankle exercise movements has a main-frame with a seat and upwardly extending columns at either side to support a “U” shaped sub-frame, mounted so that it pivots about a horizontal axis passing very nearly through the ankles of a seated user and interconnecting linkages simultaneously enforcing ankle inversion, with plantarflexion and then ankle aversion, with dorsiflexion, about perpendicularly intersecting axes, while resisting such movements, so as to provide bidirectional ankle exercises according to a progressive resistance program, thus strengthening the ankle muscle groups for enhanced balance and dynamic stability.