Abstract: An improved muscle exercise and rehabilitation apparatus, which includes a rotary actuator mounted for linear movement along a longitudinal path of movement, and a seat assembly which is mounted for movement along a lateral path of movement, and with the longitudinal path disposed on one side of the lateral path and having one end which intersects the lateral path at a medial location along the length of the lateral path. Also, the rotary actuator is mounted so as to be laterally offset from its supporting post so as to permit the actuator to rotate a full 360.degree. about a vertical axis, and a full 360.degree. about a horizontal axis. The resulting flexibility in the orientation and positioning of the components of the apparatus permits the apparatus to be readily configured to perform a variety of exercising routines, including gravity eliminated exercises. A novel automatic positioning system for the seat assembly and actuator is disclosed, and a novel patient stabilizing system is also disclosed.