Lateral HeadLateral Head of Triceps Brachii

armsCaput laterale musculi tricipitis brachii

The lateral head of the triceps is the outer section on the back of the upper arm. It is the part you can see from the side, and it produces the horseshoe shape.

Lateral Head highlighted on an anatomical figure, from behind.
Where it sits, from behind.

The lateral head sits on the outside of the upper arm bone, above the shallow groove where the radial nerve crosses. It is the most superficial and most visible of the three heads: the sharply defined outer edge of the back of the arm, and the upper half of the horseshoe outline that the triceps makes on a lean arm.

It only crosses the elbow, so unlike the long head its length does not change with arm position. Whatever you are doing with your shoulder, the lateral head is working through the same range.

Its distinctive property is when it contributes. Studies of elbow extension consistently find the lateral head increasing its share as the resistance goes up, where the medial head is active from the lightest efforts. In practical terms it is the head recruited most by heavy work.

Training notes

Heavy pressing loads it well — close-grip bench press, dips, and any press where the elbows track close to the body. Pushdowns with real weight do the same.

Because its length does not change with arm position, no elbow position specifically targets it. What changes its share of the work is load, not geometry.

It is the most visible head and therefore the one most people are trying to develop when they train arms for appearance. It is also the one that heavy compound pressing already covers, which is worth knowing before adding isolation volume.

Anatomy

Origin
  • Posterior surface of the humerus, above and lateral to the radial groove
Insertion
  • Olecranon of the ulna, through the common triceps tendon
Actions
  • Extends the elbow, contributing most when the resistance is heavy
Innervation
Radial nerve (C6–C8)

Exercises

Antagonists

Synergists