Latissimus dorsi
The broadest muscle in the body, running from your lower back to the front of your upper arm.
- Type
- Muscle
- Region
- Shoulder
- Standard name
- m. latissimus dorsi
- Origin
- Spinous processes of the lower thoracic and all lumbar vertebrae, sacrum, iliac crest and lower ribs, via the thoracolumbar fascia
- Insertion
- Floor of the intertubercular groove of the humerus
- Actions
- shoulder extensionshoulder adductionshoulder internal rotation
- Verify
- TA2 2231 TA98 A04.3.01.006
What it is
The widest muscle in the human body — latissimus dorsi, broadest of the back. It arises across an enormous span: the lower half of the spine, the sacrum, the back of the pelvis and the lower ribs, mostly by way of the thoracolumbar fascia, a large diamond of dense connective tissue across the lower back.
From that huge origin its fibres converge sharply, sweep around the side of the ribcage, spiral, and insert by a narrow tendon into the front of the humerus. The spiral is worth noticing: fibres that start lowest end up highest on the humerus.
Its lower border forms the back wall of the armpit.
What it does
Extends, adducts and internally rotates the shoulder. In plain terms: it pulls your arm down and backward, and inward towards your body.
That makes it the main muscle of climbing and of pulling yourself up — anything where your arms are above you and your body has to come to them. It is also the muscle of a swimming stroke's pull phase and of driving a crutch or a paddle down.
Because it attaches to the pelvis and lumbar spine as well as the arm, it links the upper limb to the trunk directly, and it contributes to trunk movement when the arm is fixed.
What loads it
Pull-ups, chin-ups, rows, pulldowns, climbing, and swimming.
The pull-up is the most complete loading of it available without equipment, with the negative pull-up as the route there. The inverted row loads it horizontally at whatever fraction of bodyweight you choose, and even a dead hang loads it isometrically.
What is commonly got wrong about it
"Lat spread" and V-taper as training outcomes. The visible width of the back is a combination of muscle size, ribcage shape and pelvis width. Training makes the muscle bigger; the frame it sits on is not adjustable.
That it is a back muscle in the postural sense. It moves the arm. It does not hold your spine up — that is the erector spinae group and the deeper spinal muscles.
"Mind-muscle connection" claims about feeling it work. You can certainly feel a pulling movement in the region. Whether attention changes which fibres are recruited in a way that matters over months is a much larger claim, and the research on it is limited and mixed.
That straight-arm pulldowns isolate it. Teres major does the same three actions and is loaded alongside it in essentially everything.