Controlling an upper-limb prosthesis is challenging for transhumeral amputees. A central problem is the inability to move multiple prosthetic joints at the same time. With a body-powered prosthesis, an amputee uses shoulder motion to sequentially move the prosthetic elbow and lock it in place before switching to operation of the wrist, hand, or hook. With a myoelectric prosthesis, surface electromyographic signals from the residual biceps and triceps are used to control a motorized arm. Again, sequential control is required, as the biceps and triceps can only operate one joint at a time. The use of these prostheses rarely becomes intuitive. The patient is forced to use chest, shoulder girdle, or upper-arm muscles to move the prosthetic elbow, wrist, and hand in a slow, complex, and burdensome manner. Often, expensive prostheses are left untouched in the patient's closet because the sequence of movements that is required to effectively use the prosthetic arm actions does not occur in a workable time frame for the patient.