1. The supinator muscle (A) laterally rotates the radius around the ulna. (B) is the only muscle producing supination. (C) may produce flexion at the elbow. (D) medially rotates the ulna around the radius. (E) is supplied by the median nerve. 2. The trapezius muscle (A) is inactive in elevation of the arm. (B) has the same nerve supply as the teres major. (C) aids in lateral rotation at the gleno-humeral joint. (D) is paralysed in an upper trunk brachial plexus lesion. (E) acts as a mechanical couple in lateral (upward) rotation of the scapula.