Lats (latissimus dorsi)

The broadest muscle in the body, sweeping from the lower spine up to the arm. It drives every pull-down and pull-up and gives the back its V-shape. It also links the arm to the opposite hip through the fascia.

This muscle in 3D

Drag to rotate · scroll to zoom — see the shape, origin and insertion of the lats (latissimus dorsi). 3D model via Sketchfab (CC-BY).

Anatomy

Muscles: Latissimus dorsi

Origin: Lower six thoracic vertebrae, lumbar spine, sacrum, iliac crest and lower ribs (via thoracolumbar fascia).

Insertion: Intertubercular groove of the humerus (front of the upper arm).

Actions:

• Shoulder extension (pull the arm down and back)
• Shoulder adduction (arm to the side, e.g. pull-up)
• Internal rotation of the humerus
• Assist trunk and pelvis stability

How the muscle works

Because it wraps from the back of the trunk to the front of the arm, contracting it pulls the arm down, back and inward — the essence of a pull-up or row. It also transmits force diagonally across the back to the opposite glute.

Fibre-type bias: Mixed — responds to both heavy pulling and higher-rep work.

Functional role: Pulling and climbing; bringing the body up to the hands (pull-ups) or the hands to the body (rows).

Common problems

• Tightness limiting overhead reach
• Strain in heavy pulling / rowing
• Underuse contributing to poor pulling posture

Training & stretching

Pull-ups, lat pulldowns, rows (barbell, dumbbell, cable), straight-arm pulldowns.

Overhead reach and side-bend; hanging from a bar.

Fix or train this

• Neck & Shoulder Pain
• Lower Back Pain
• Build Muscle (Plateau)