Teres Major

backMusculus teres major

The teres major is a thick strap from the bottom corner of the shoulder blade to the upper arm, and it does almost exactly what the lat does. It is why the back of the armpit looks full on a developed back.

The teres major runs from the lower outside corner of the shoulder blade forward to the upper arm bone, wrapping under the armpit on the way. It is short, thick and easy to find on a lean back: it forms the rounded ridge at the rear edge of the armpit, just above the lat.

It is nicknamed the lat's little helper, and the nickname is accurate. It attaches to the arm right beside the latissimus dorsi and pulls in the same three directions — arm down, arm in, arm rotated inward. Anything that trains the lat trains this, and there is no movement that separates them.

The one thing that distinguishes it is where it starts. The lat is anchored to the spine and pelvis, so it moves the arm relative to the torso. The teres major is anchored to the shoulder blade, so it moves the arm relative to the shoulder blade — which means the shoulder blade has to be held steady by something else for it to work, and that something else is the rhomboids and the trapezius.

Do not confuse it with the teres minor directly above it. They sit side by side on the same edge of the shoulder blade and do opposite things: teres major rotates the arm inward, teres minor rotates it outward. Teres minor is part of the rotator cuff and teres major is not.

Training notes

There is no teres major exercise and there does not need to be one. It works on every pulldown, pull-up and row, and it grows with the back work you are already doing.

If anything emphasises it, it is pulling with the arm moving in the plane of the body rather than out to the side — a straight-arm pulldown, or a pullover — where the arm travels through a long arc from overhead to the hip with the elbow relatively straight. Because the teres major does not cross the elbow, movements that take the biceps out of the equation give it a larger share of the work.

Visually it matters more than its size suggests. Along with the lat and the rear deltoid, it fills in the area where the arm meets the back, which is the part of a developed back that reads as thickness rather than width.

Anatomy

Origin
  • Posterior surface of the inferior angle and lower lateral border of the scapula
Insertion
  • Crest of the lesser tubercle of the humerus, on the medial lip of the intertubercular sulcus
Actions
  • Adducts the arm toward the midline
  • Extends the arm from a flexed position
  • Internally rotates the humerus
Innervation
Lower subscapular nerve (C5–C6)

Teres major is a thick, rounded muscle arising from the back of the lower outer corner of the scapula. It passes forward and laterally beneath the armpit and inserts on the medial lip of the intertubercular sulcus, immediately behind and medial to the latissimus dorsi tendon. The two tendons are separated by a bursa and are frequently blended.

Its three actions are identical to those of latissimus dorsi, which is why the older name for it — the lat's assistant — has survived. The mechanically significant difference is proximal: latissimus dorsi arises from the axial skeleton, so it moves the humerus relative to the trunk, while teres major arises from the scapula and moves the humerus relative to the scapula. Its effectiveness therefore depends on the scapula being stabilised by the rhomboids and trapezius.

It is not part of the rotator cuff, despite lying alongside teres minor on the same border of the same bone and despite the similarity of the names. Teres minor externally rotates and blends into the cuff tendon; teres major internally rotates and does not contribute to the joint capsule at all.

Its upper and lower borders help define the triangular and quadrangular spaces of the shoulder, through which the circumflex scapular vessels and the axillary nerve pass.

Under load

It is recruited by every movement that draws the humerus down or back — pulldowns, pull-ups, rows, pullovers — and there is no movement that separates it from latissimus dorsi.

Movements performed with a relatively extended elbow give it a proportionally larger share of the work, since the elbow flexors are removed from the equation.

Its visible contribution is to the fullness at the posterior fold of the axilla, where it forms a distinct rounded ridge above the latissimus dorsi on a lean and developed back.

Exercises

No exercise in the library names Teres Major yet. Nothing has been invented to fill the gap — a false reference costs more than an absent one.

Antagonists

Synergists