Lower TrapeziusAscending Part of Trapezius

backPars ascendens musculi trapezii

The lower trapezius runs upward from the middle of your back to the shoulder blade and pulls it down and back. It is the least trained third of the trapezius and the one that makes reaching overhead possible.

These fibres start along the spine at the level of the ribcage and run upward and outward to the inner end of the ridge on the shoulder blade. Because they approach from below, they pull the shoulder blade down — the opposite direction to the upper trapezius, in the same muscle.

The obvious action is depression: pulling the shoulders down away from the ears. The more important one is less obvious. When you lift your arm overhead, the lower trapezius pulls down on the inner end of the shoulder blade's ridge while the upper trapezius pulls up on the outer end, and the shoulder blade spins between them so the socket turns to face upward. That rotation is what lets the arm finish vertical rather than stopping short.

So the same muscle contains fibres that fight each other in one movement and cooperate in another. The reason is geometry: they pull on opposite sides of the shoulder blade's pivot, so pulling together in a straight line cancels out, while pulling together in a rotation adds up.

The lower trapezius sits under a thin layer of tissue and no other muscle, so on a lean, developed back it is visible as a shallow V shape running from the shoulder blades down toward the middle of the spine.

Training notes

This is the part of the trapezius that most reliably gets nothing, and the one with the clearest payoff for training it. The front of the shoulder is pulled forward and up by daily life and by every pressing movement; the lower trapezius is one of the main things pulling in the other direction.

The movements that train it share one feature: the arm finishes above shoulder height while the shoulder blade travels down and back. Prone Y raises, overhead presses taken to a genuine lockout, face pulls with the elbows kept high, and controlled lat pulldowns all qualify. Weight is beside the point — these work at loads that look trivial and stop working as soon as the load makes the position sloppy.

A common cue that gets it wrong: pulling the shoulder blades down and holding them there through every exercise. That trains depression while preventing upward rotation, which is half the muscle's job. The shoulder blade is supposed to move when the arm moves.

If overhead pressing feels blocked before the arms are vertical, or if the shoulders creep up toward the ears during a set of pulldowns, the lower trapezius is a reasonable place to spend a few sets a week.

Anatomy

Origin
  • Spinous processes of the fourth to twelfth thoracic vertebrae
Insertion
  • Tubercle at the medial end of the spine of the scapula
Actions
  • Depresses the scapula, drawing it down toward the opposite hip
  • Rotates the scapula upward, working with the upper trapezius and the serratus anterior
  • Holds the scapula down and back against the pull of the muscles at the front of the shoulder
Innervation
Accessory nerve (CN XI), with sensory fibres from C3–C4

Exercises

Antagonists

Synergists