Experimental Apparatus for Creating a Virtual Impairment and for Assisting in Motor Learning. Picture (left) and diagram (right) of experimental setup. The robot makes use of a linear motor with two forcer coils and a V-shaped linkage to accommodate and drive motion of the robot's apex in the parasagittal plane. The apex is attached through a padded brace and revolute joint to the subject's lower shank. Subjects wore a harness attached to an overhead frame to catch them in case they fell. The robot created a virtual impairment by pushing upward on the subject's lower shank during the swing phase of gait, making the subject step abnormally high. The robot also assisted the subject in learning to compensate for the virtual impairment with small step height errors by helping counteract the impairment.