Extension (anatomy) in the context of "Chin-up bar"

A pull-up is an upper-body strength exercise. The pull-up is a closed-chain movement where the body is suspended by the hands, gripping a bar or other implement at a distance typically wider than shoulder-width, and pulled up. As this happens, the elbows flex and the shoulders adduct and extend to bring the elbows to the torso.

Pull-ups build up several muscles of the upper body, including the latissimus dorsi, trapezius, and biceps brachii. A pull-up may be performed with overhand (pronated), underhand (supinated)—sometimes referred to as a chin-up—neutral, or rotating hand position.