Triceps Brachii Muscles
The triceps brachii muscle (Latin for "three-headed arm muscle") is the large muscle on the back of the upper limb of many vertebrates. It is the muscle principally responsible for extension of the elbow joint. The triceps is an extensor muscle of the elbow joint and an antagonist of the biceps and brachialis muscles. It can also fixate the elbow joint when the forearm and hand are used for fine movements, e.g., when writing. It has been suggested that the long head fascicle is employed when sustained force generation is demanded, or when there is a need for a synergistic control of the shoulder and elbow or both. The lateral head is used for movements requiring occasional high-intensity force, while the medial fascicle enables more precise, low-force movements.