Long HeadLong Head of Triceps Brachii

armsCaput longum musculi tricipitis brachii

The long head of the triceps is the largest of the three and the only one that crosses the shoulder. It is why overhead extensions train the back of the arm differently from pushdowns.

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

The long head starts on the shoulder blade, just below the socket, and runs down the inner back of the upper arm between the teres major and teres minor. It is the biggest of the three heads and the one that gives the back of the arm its thickness where it meets the shoulder.

Crossing two joints is what makes it different. It straightens the elbow like the other two heads, but it also pulls the whole arm backward and in toward the body — the same directions the lat pulls. That is why the long head works during pulldowns and rows even though nothing about those is a triceps exercise.

The practical consequence is about length. A muscle crossing two joints can be shortened at both ends at once, and when the elbow is at your side and already extended, the long head has very little left to contract. Raise the arm overhead and it is stretched at the shoulder, so it has its full range available at the elbow.

That is the whole argument for overhead triceps work, and it is the clearest example in the arm of why the position of a joint you are not training changes what happens at the one you are.

Training notes

Overhead extensions — dumbbell, cable, or a French press — are the movement, and the distinguishing feature is simply that the upper arm points up rather than down. Everything else about the exercise is secondary to that.

Skull crushers with the arms angled back past vertical get part of the way there. Pushdowns and dips do not: the arm is at or behind the side, so the long head is short at the shoulder throughout.

It also contributes to keeping the arm tight to the body during heavy pressing and pulling, which is one reason the back of the arm is rarely completely untrained even in a program with no direct triceps work.

If only one triceps movement fits in a session, an overhead variation covers more of the muscle than a pushdown does.

Anatomy

Origin
  • Infraglenoid tubercle of the scapula
Insertion
  • Olecranon of the ulna, through the common triceps tendon
Actions
  • Extends the elbow
  • Extends the arm at the shoulder, drawing it backward
  • Adducts the arm toward the body
Innervation
Radial nerve (C6–C8)

Exercises

Antagonists

Synergists