Overcoming abnormal joint torque patterns in paretic upper extremities using triceps stimulation

The goal of this research project was to quantitatively assess whether transcutaneous triceps stimulation can overcome the expression of abnormal torque patterns in the paretic upper limb of subjects with hemiparetic stroke. Abnormal torque patterns consist of strong coupling between shoulder abduction (SAB) and elbow flexion (EF) or between elbow extension (EE) and shoulder adduction (SAD) torques. Both patterns reduce the active range of motion during arm movements. Eight chronic stroke subjects with moderate to severe (Fugl-Meyer assessment scores of 21/66-36/66) upper limb motor impairment participated in this study. Shoulder and elbow joint torques were measured with a 6-degrees-of-freedom load cell under isometric conditions, while the triceps muscle was stimulated to generate EE torques. At the same time the subjects were asked to lift up their arm to generate different SAB torque levels. The obtained isometric results showed that electrical stimulation can overcome abnormal torque patterns in chronic stroke subjects while generating SAB. This is likely to have potential benefits to increase the reaching workspace of the paretic arm.