Description of experimental setup. (a) Photograph of the Assisted Rehabilitation and Measurement (ARM) Guide. A motor (M) actuates a hand piece and forearm trough (T) attached to a user's arm (A) back and forth along a linear track. A six-axis force sensor (F) measures the interaction forces between the user and the device. The ARM Guide can be oriented on a vertical elevation axis (E) and horizontally on a yaw axis (Y). (b) Example of an unassisted (solid line) and motor-assisted (dashed-line) reach by a hemiparetic subject along the ARM Guide. (c,d) Horizontal and vertical arrangements of the targets used for free reaching assessment, free reaching therapy, and robot-based therapy.