The triceps are a major muscle of the upper arm in the human body. The triceps run along the humerus (the main bone of the upper arm) between the shoulder and the elbow. Along with the biceps, it allows for extension and retraction of the forearm. When the triceps are tensed, the forearm extends and the elbow straightens; if the triceps are relaxed and the biceps tensed, the forearm retracts and the elbow bends. The triceps also serve to stabilise the shoulder joint at the top of the humerus; this is a key role as the shoulder is a relatively unstable joint. The bottom of the triceps are also involved in retracting the capsule of the elbow joint when the forearm extends, thereby allowing the elbow joint to be straightened successfully. The muscle is supplied with oxygen and nutrients by branches of the deep brachial artery. It is also enervated by four branches of the radial nerve. Both the artery and the nerve continue into the lower forearm beyond the triceps.
Written and medically reviewed by the Healthline Editorial Team
In Depth: Triceps brachii