A weight-lifter has increased the frequency of his training to prepare for an upcoming competition. Recently he noticed a loss of sensation over the lateral side of his forearm, and his ability to supinate is weaker than normal. Which of the following could account for his symptoms?
A. damage to the medial cord of the brachial plexus
B. hypertrophy of the coracobrachialis muscle
C. impingement of the radial nerve
D. partial tearing of the brachialis tendon