Learn about the triceps brachii muscle, a three-headed muscle of the arm that extends the forearm and shoulder. Find out its origin, insertion, innervation, blood supply and clinical notes. The triceps brachii, often referred to as the triceps (‘tri’ meaning ‘three’, and ‘cep’ meaning ‘head’), is a large three-headed muscle at the back of the upper arm. Its shape may resemble a horseshoe, especially from the back. The triceps is primarily responsible for extending the elbow. Build bigger, stronger arms with the 13 best triceps exercises. From classic dips to cable pushdowns, these moves target all three triceps heads for maximum growth and definition. Learn how to train smarter for serious gains! Learn the most effective triceps exercises to target all three tricep heads and work the muscles from all angles to build strong triceps. Get detailed triceps workout instructions for triceps kickbacks, triceps dips, diamond push-ups, and more.