Method: Stand with the back toward the inside of the doorframe. While keeping the arm straight, hyperextend the left arm above the midpoint between the hip and shoulder. Grasp the doorframe with the left hand with the thumb pointing down. Externally rotate the arm (roll the biceps toward the top).
Affected Body Part: Most-stretched muscle: Left pronator teres. Lesser-stretched muscles: Left brachialis, left brachioradialis, left pronator quadratus, left subscapularis, left teres major.
You can also do this exercise with a firmly planted vertical pole. To maximize the stretch, keep the elbow straight. After rolling the biceps upward, you can enhance the stretch by inwardly rotating the back toward the hyperextended arm (see figure).