The latissimus dorsi is the largest muscle in the upper body. It spans from the lower spine and pelvis all the way up to the upper arm, covering most of the mid and lower back. Despite being one of the most trained muscles in any serious program, it's also one of the most misunderstood in terms of how it actually works.
Anatomy and Location
The latissimus dorsi is a broad, flat muscle that covers the majority of the posterior trunk below the shoulder blades. The name translates from Latin as "broadest muscle of the back," which is accurate. When developed, it creates the characteristic V-taper silhouette.
It is classified as a superficial muscle of the back, meaning it sits close to the surface rather than deep against the spine. It overlaps with the lower trapezius and partially covers the posterior inferior serratus.
Origin and Insertion
The lats have a wide origin across multiple structures:
- Spinous processes of T7 through L5 (the lower thoracic and all lumbar vertebrae)
- Thoracolumbar fascia, which connects it to the sacrum and posterior iliac crest
- The posterior surface of the lower three or four ribs
- The inferior angle of the scapula in many individuals
All of these fibers converge into a single flat tendon that inserts on the intertubercular groove of the humerus, on the anterior surface of the upper arm. The transition from broad origin to narrow insertion is what gives the muscle its fan-like shape.
Primary Functions
The lats perform several actions at the shoulder joint:
Extension: Moving the arm from a raised position down toward the body. This is the primary action in pull-ups and pulldowns. When your arm is overhead, the lat is stretched. As you pull down, it contracts to bring the humerus into extension.
Adduction: Pulling the arm toward the midline of the body. In rowing movements, this is what draws your elbows back and in.
Internal rotation: Rotating the humerus inward. This is a smaller contribution but relevant to pressing movements and overall shoulder mechanics.
The lats also play a critical role in trunk stabilization. During heavy deadlifts and squats, a braced lat prevents the spine from going into flexion under load. This is why cues like "protect your armpits" or "bend the bar" exist on the deadlift. They're cueing lat engagement, not just arm position.
Why the Lats Matter for Every Major Lift
Most lifters think of lat training as a size goal. Bigger lats, wider back. That's part of it. But in a powerbuilding context, the lats are a stability and force transfer muscle across all three competition lifts.
On the squat, a braced lat keeps the torso upright under load. If your upper back rounds out of the hole, your lats aren't doing their job.
On the deadlift, lat engagement keeps the bar close to the body and prevents the lower back from taking over. A lat that fires late or not at all is one of the most common reasons for a forward bar drift and a slow pull off the floor.
On the bench press, retracting and depressing the shoulder blades requires active lat involvement. If you've ever been cued to "pull the bar to your chest" rather than just lower it, that's a lat cue. It stabilizes the shoulder girdle and keeps the joint in a safe, powerful position through the eccentric.
Training the Lats Effectively
The lats respond to both vertical pulling (pull-ups, pulldowns) and horizontal pulling (rows). Neither alone is sufficient. Vertical pulls emphasize shoulder extension and develop the sweep. Horizontal pulls emphasize adduction and build thickness through the mid-back where the lats overlap with the teres major and rhomboids.
Full stretch at the top of the movement matters. Cutting the range of motion on pull-ups or rows to move more weight reduces the lat's time under tension at its most lengthened position, which is where much of the growth stimulus comes from.
Frequency should match your pressing frequency. If you press twice a week, you should pull twice a week. The anterior and posterior shoulder systems need to stay balanced or you will eventually accumulate enough structural imbalance to cause injury.
