The PAAD flexes and extends the elbow, and it abducts and adducts the shoulder, where "abduction" is away from the side of the body, and "adduction" is towards it. Elbow extension occurs simultaneously with shoulder abduction, and elbow flexion occurs simultaneously with shoulder adduction. At the same time as the movements, vibrators are utilized to activate muscle spindle Ia receptors in the muscles of the arm to exaggerate the perception of movement.

Subjects will don a shirt with pockets at the elbow and shoulder in each of which a muscle vibrator is located. The subject will then place the affected arm in the PAAD. The PAAD will range the affected arm, at the shoulder in the adduction-abduction direction, and at the elbow in the flexion-extension direction. The subject will assist volitionally this motion, and visual feedback of the level of their assistive torque will be provided along with a target torque level. The muscle vibrators will alternate from one side of each of the 2 joints to the other as the motion reverses, vibration always being applied to the lengthening muscles. This treatment will last 30 min in each session.

The PAAD measures the strength at the elbow and shoulder by recording the torque applied by the subject to the device with the elbow and shoulder during maximal efforts.