what the role of biceps
The biceps brachii crosses two joints - the shoulder and the elbow - so it can influence movement of both joints. The biceps brachii can bring about a variety of movements when it shortens, including: Supination: turning the palm upward. Let one arm hang with your palm facing behind you. When your biceps brachii contracts, it tugs on the radius and pulls it to the outside. This turns your palm to face forward.