The latissimus dorsi (lats) is one of the coolest muscles in the body. Here’s what they look like on one of the most muscular people of all time, Jay Cutler:

Here are all the most important things to know about the lats:

Anatomy Overview

The lats are a fan-shaped muscle that extend from various parts of the spine and hips to the upper arms.

They are divided into upper, middle, and lower regions, each attaching to the arm at slightly different points, which affects how they function during exercise.

Function and Mechanics

The lats are not major spine movers but significantly influence upper body movement in the shoulder girdle (the upper arm, collar bone, and shoulder blade).

Understanding fiber direction is crucial: horizontal fibers in the upper lats and vertical fibers in the lower lats have different functions and implications for training.

You can think of it this way: horizontal lat fibers pull the arms horizontally (front-back), while vertical lat fibers pull the arms vertically (up-down).

Practical Training Tips

Depending on the angle and direction of the resistance, different exercises can more effectively target specific regions of the lats.

Rows will generally train more of the horizontal or upper lats.

Pull-downs will generally train more of the vertical or lower lats.

Stability

Ensure stability during any lat exercise to isolate the lats properly and prevent other muscles from compensating. Use lat pull-down pads, benches, chest-supported machines, and seatbelts to do this.

Single vs. Double Arm Exercises

Single-arm variations can enhance the length of the lats and muscle engagement by allowing for adjustments in bony position and resistance alignment.

With a single arm, you can orient your upper arm across your body, which can lengthen each of the lats more than if you were using two arms simultaneously.

This is because the rib cage acts like a pulley for the lats, influencing how the muscle stretches and contracts. Keeping the arm close to the body during rows or pull-downs will increase lat engagement.

I just posted a 30-minute video lecture on YouTube covering all of this in more detail. Check it out and subscribe to the channel if you want to see more videos like it: