The Triceps Brachii muscle is a large muscle on the back of the upper arm. It is the muscle responsible for elbow extension, otherwise known as straightening the arm. Triceps Brachii is the Latin word for 3-headed arm muscle. This brings me to the break-down of the 3 heads of the Triceps Brachii.
The Long Head
The long head originates from the infraglenoid tubercle of the scapula and it extends distally anterior to the Teres Minor and posterior to the Teres Major. The role of this head is to extend and adduct the shoulder. The further away the arm is from the abdominal region, the more this head is recruited. So for example exercises that would be fantastic choices for the long head would be triceps extensions on an incline bench and overhead triceps extension work.
The Medial Head
The medial head originates distally from the groove of the radial nerve; from the dorsal surface of the Humorous; from the medial intermuscular septum; and its distal part also originates from the lateral intermuscular septum. The medial head is mostly hidden by the lateral and long heads, and is only visible distally on the Humorous. The medial head is considered the ‘workhorse’ of the heads so working all triceps exercise would recruit this head.
The Lateral Head
The lateral head originates from the dorsal surface of the Humorous, lateral and proximal to the groove of the radial nerve, from the greater tubercle down to the region of the lateral intermuscular septum. By performing exercises on a flat bench you will recruit this head alongside the long head also. The more the upper arm is internally rotated the more the lateral head would be recruited. All heads insert on the Olecranon process of the ulna.
The Triceps Brachii muscle group crosses over radial nerve C6, 7,8 and T1.