biceps brachii
Biceps brachii supinates the arm, but it is not innervated by the radial nerve--instead, it is innervated by the musculocutaneous nerve. So, it would not be affected by a radial nerve injury. Brachialis is also innervated by the musculocutaneous nerve, but it is only involved with flexing the forearm--it is not a supinator. Brachioradialis flexes the elbow and assists in pronation and supination--it is innervated by the radial nerve and would be paralyzed after a radial nerve injury. Flexor carpi radialis is a flexor, not a supinator--it is innervated by the median nerve. Finally, supinator is innervated by the deep radial nerve.