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In general terms, abduction, in the anatomical sense, is classified as the motion of a limb or appendage away from the midline of the body. In the case of arm abduction, it is the movement of the arms away from the body within the plane of the torso (coronal plane). The abduction of the arm begins with the arm in a position parallel to the torso and the hand in an inferior position, continues with the movement of the arm to a position perpendicular to the torso, and ends with the movement of the arm so that the humerus is raised above the shoulder joint and points straight upward. (The upper extremity action during a jumping jack can is exemplary of the full range of motion for arm abduction.) The primary muscles involved in the action of arm abduction include the supraspinatus, deltoid, trapezius, and serratus anterior.[1]