An exercise apparatus has left and right foot skates which are constrained to move back and forth in reciprocal fashion. Left and right foot platforms are movably mounted on respective foot skates and constrained to move up and down in reciprocal fashion. The apparatus may be operated in different modes of operation, including a first mode, wherein the foot skates are free to move back and forth and the foot platforms are free to move up and down; a second mode, wherein the foot platforms are free to move up and down, but the foot skates are locked (or biased) against movement; and a third mode, wherein the foot skates are free to move back and forth, but the foot platforms are locked (or biased) against movement. Resistance may be provided to back and forth movement of the foot skates and/or up and down movement of the foot platforms.