Alternating Dumbbell Curls 08/30/2007 Fitness The biceps brachii consists of two muscular heads: the short and the long head. Functionally, the biceps can do two things: flex the elbow and supinate the forearm. Supination is simply the act of turning the palms face up. The alternating dumbbell curl is a great way to work the biceps. The followi...