Rotational Motion Due to Skin Shear Deformation at Wrist and Elbow

The hanger reflex is an illusion phenomenon that induces strong force perception and rotational motion, and it occurs in multiple parts of the body. A potential application of this phenomenon is in upper limb rehabilitation for patients with upper-limb paralysis involving arm rotation. However, the only upper limb movements that have been confirmed in this phenomenon are the inward and outward movements of the wrist, which limits the applicable tasks. Therefore, we attempted to apply the hanger reflex to the elbow and use it simultaneously with the wrist. This phenomenon occurs due to shear deformation of the skin, so shear deformation was presented to the skin on the elbow. When shear deformation of the skin was presented to the elbow in the same manner as in previous studies applied to the wrist, movement and force perception of pronation and supination of the elbow were confirmed. The results of an experiment in which the hanger reflex was simultaneously presented to the elbow and wrist showed that each region independently perceived motion and force.