How the Serratus Posterior and Lats Work Together

When you pull something, your lats do the work, which includes extending, adducting, and internally rotating your shoulders. Your serratus posterior, on the other hand, quietly controls the position of your ribs and the stability of your thorax, giving your lats the support they need to work efficiently. If you don't have that background stabilization, your pulling strength stops growing, and compensation patterns start to form.

What the Serratus Posterior and Lats Actually Do​

The back is made up of the serratus posterior and the latissimus dorsi, but they don't do the same thing. The serratus posterior muscles are thin and layered. They connect the ribs to the spine. Their main job is to move the ribs when you breathe, which helps keep your thorax stable but doesn't move your big limbs.
The latissimus dorsi muscle tells a different story. It's a big, strong muscle that moves the shoulder outward, inward, and rotates internally. Lat activation makes pulling exercises like rows, pull-ups, and pulldowns possible. This makes the lats a main mover instead of a stabilizer.
Both of these muscles work in a similar area, but their jobs don't exactly cross. Knowing what each muscle does helps you train smarter and understand your back's feelings better while you work out.

How the Serratus Posterior and Lats Connect Anatomically​

These two muscles are layered across the middle and lower back. They share the same body space, but they don't have the same attachments or roles. As you can see, the serratus posterior is located below the latissimus dorsi. It connects to the thoracic spine and angles outward toward the ribs. As they go from the lower back and pelvis to the upper arm, the lats cover a lot of the area below them. This is because the latissimus dorsi crosses over the rib cage, connecting with the serratus posterior in space but not in terms of its muscular role. Knowing about the nature of the back muscles means realizing that being close doesn't mean you're a partner. During a pulling motion, you may feel tension in the same area, but each muscle is reacting to different mechanical demands because of how it is attached and what it does.

How These Muscles Coordinate During Real Movement​

Your lats do most of the work when you pull a bar toward your chest or drive your arms down during a straight-arm pulldown. In the background, your serratus posterior does a less important job. The latissimus dorsi muscle moves your shoulder back, and the serratus posterior superior muscle helps keep your ribs in place by controlling how you breathe. This keeps your thoracic region stable enough to support that movement. They're not working together under a co-contract to reach the same goal. Instead, they are working on different tracks that sometimes cross each other. Your ribs react to load by changing the way you breathe, and the serratus posterior adapts to match. That background stabilization helps your latissimus dorsi stay in the right place so it can create force effectively, without either muscle going beyond its intended mechanical role.

When the Serratus-Lat Partnership Breaks Down and Costs You​

When that background stabilization is upset, it doesn't make a loud noise. Instead, it shows up as stopped pulling strength, compensated movement patterns, or a persistent tension that never quite goes away. The latissimus dorsi loses its mechanical advantage before it even starts to work when your thoracic posture falls into too much flexion. When you're already pulling from a weak position, the serratus posterior inferior can't control rib movement well. You won't notice a specific muscle failing; what you will notice is a general breakdown in how your back loads when you pull. Make ups sneak in through the lower back, upper traps, or neck. Just because one muscle stopped working doesn't make you weaker. You're weaker because the coordinated system that helps you transfer force effectively no longer has a solid base.

How to Train the Serratus Posterior and Lats as a Team​

To train these two muscle groups together, you must first understand that you are not trying to isolate either one. Instead, you are creating situations where both can do their jobs. Pay attention to controlled pulling motions that let your scapula move all the way through its length without collapsing or flaring out too soon. Keep your breathing steady so that the upper and lower serratus posterior can support your ribs during the whole rep. Your lats and serratus muscles work well together when your trunk stays still, and your shoulder movements are smooth and not strained. Focusing on posture, breathing rhythm, and load management over sensation-chasing will help you train the serratus posterior and lats. When both muscles do what they're supposed to do, your pulling strength goes up, and your thoracic mechanics stay in order while you're lifting.