Pec Deck Machine

A pec deck is a machine designed to increase strength and muscle mass in the chest. It's so effective that the American Council on Exercise ranked it as one of the best exercises for building chest muscles.You have two pectoralis majors or "pecs," one on each side of your chest. These large muscles help you move your shoulder. These muscles help pull your arm across the front of your body. Injury to the pectoralis major can cause shoulder pain and limit your ability to use your arm fully.