Collapsed Ribcage + Serratus Anterior: The Missing Muscle Most People Never Train
If your posture collapses, your upper back feels weak, and your breath lives in your upper chest, it is easy to assume you need to stretch more or “open your chest.”
But for many people, the issue is not flexibility.
It is support.
A collapsed ribcage pattern often shows up when your shoulder blades cannot stay organized on your ribs. When that support is missing, your neck, upper traps, and chest muscles try to create stability and pull air in. That is when breathing drills start to feel frustrating and posture cues never stick.
One of the most overlooked muscles in this whole loop is serratus anterior.
Most people only hear about serratus in the context of “winging shoulder blades.” But serratus is also a key player in:
keeping the shoulder blade connected to the ribcage during reach
overhead motion without shrugging
trunk rotation and integration
making ribcage expansion feel more possible with less effort
This post will break down what serratus does, how to tell if it is under-working, and a simple 3-drill sequence you can practice in minutes.
What the serratus anterior actually does (in plain language)
1) It brings the shoulder blade forward and keeps it anchored on the ribs
Yes, serratus helps protract the shoulder blade (it glides forward around the ribcage). But the bigger point is this: serratus helps the scapula stay connected to the ribcage while it moves.
Without that connection, many people default to one of two strategies:
pinning shoulder blades back for stability
losing scapular control and shrugging or winging
Serratus supports the middle path: wide, stable, and mobile.
2) It helps you reach overhead without neck takeover
Serratus contributes to upward rotation and posterior tilt of the scapula when you reach overhead.
In real life: it helps your arms go up without your ribs popping up and your upper traps doing all the work.
3) It often makes breathing feel easier by creating upper back “width”
When serratus is doing its job, many people feel a sense of upper back support and space. That often makes it easier to feel expansion into the back and side ribs without pulling air in with the neck.
You are not “doing a better breath.” You are building a better shape for breathing.
4) It participates in reaching and rotation patterns that coordinate with the trunk
Serratus often works with the trunk during reach and rotation. A simple way to think about it: the arm reaches, the shoulder blade stays connected, the ribcage can rotate without bracing.
This matters because most people can do a breathing drill on the floor, then stand up and lose it the moment they reach or rotate. Serratus helps bridge that gap.
The rope analogy: why upper traps take over when serratus is quiet
A helpful way to picture this is to think of serratus as the support that keeps your shoulder blade connected to your ribcage during reach and daily movement.
When serratus support is present:
The shoulder blade stays organized on the ribs, the upper back feels wider, and the ribs often have an easier time expanding without the neck taking over.
When serratus is weak and the upper traps compensate:
The shoulder blade loses that support on the ribcage. The system often tries to create stability higher up by recruiting the neck and upper traps. That is when posture tends to round forward and the breath can feel “stuck” in the upper chest.
Serratus vs Upper Trap
Left: serratus support helps the upper back stay wide so rib expansion feels easier. Right: weak serratus often leads to upper trap compensation and ribs can feel stuck.
How to tell if this is your pattern
You might relate to these:
your upper back feels narrow or collapsed
your shoulders drift forward and your neck feels overworked
overhead reach makes you shrug or flair your ribs
you cannot feel back rib expansion unless you force a breath
you “pin” your shoulder blades back to feel stable, but it never lasts
rotation feels stiff, jammed, or like your shoulder takes over
Quick self-checks (2 minutes)
Check 1: Forearm wall reach test
Stand facing a wall. Place your forearms on the wall at shoulder height.
Gently press into the wall, then add a small reach as if you are trying to widen your upper back.
Notice:
do your shoulders shrug immediately?
does your neck tense up?
do your ribs flare to “help”?
do your shoulder blades feel disconnected from your ribs?
If yes, serratus is a great place to start.
Check 2: Quiet inhale test
Place your hands on your side ribs.
Take a small, quiet inhale through the nose.
Notice:
can your ribs expand a little without your chest lifting?
can your neck stay calm?
If not, that often means your ribcage is missing support, not that you “need to breathe deeper.”
The Serratus Reset:
Drill 1: Forearms-on-wall reach ups (palms supinated or neutral)
Setup: Face a wall. Forearms on the wall at shoulder height. Palms can be supinated or neutral. Choose what keeps your ribs calm and your neck quiet.
Do this:
Exhale softly and let your ribs settle.
Gently press forearms into the wall.
Add a small reach so your upper back feels wide.
Slide forearms up the wall slowly.
Keep the inferior angle wide on the ribcage (no pinching back).
Inhale quietly into the back and side ribs while keeping the reach.
6 slow reps.
Key cues:
reach long, do not shrug
keep ribs organized, no flare
feel upper back width
What you should feel: effort in the side of the ribcage and under the shoulder blade, not in the neck.
Drill 2: Side-lying serratus rotation reach (90/90 hips and knees)
Setup: Lie on your side with hips and knees at 90 degrees like you are sitting in a chair. Hold a light weight straight up to the ceiling over the shoulder.
Do this:
Reach the weight toward the ceiling (gentle protraction).
Rotate your chest toward the ceiling slowly.
Option A: let the arm glide back as the ribcage rotates
Option B: bend the elbow wide for a pec-friendly opener
Return by reaching the weight back to the ceiling first, then rotate your chest back toward the front.
4 reps each side.
Key cues:
reach drives the return
keep the shoulder blade connected to ribs
no pinching between shoulder blades
This drill ties serratus to rotation in a way that feels like real movement, not isolated activation.
Drill 3: Banded protraction control (push forward and return to neutral)
Setup: Anchor a band behind you at shoulder height. Place the band around the front of the shoulder.
Do this:
Start with your arm in front of you at shoulder height, band around the front of the shoulder.
Push forward by letting the shoulder blade glide around the ribcage, keeping arm heavy in the back of the socket.
Return slowly to neutral without pinching your shoulder blades together.
8 controlled reps each side.
Key cues:
inferior angle glides wide
return to neutral, do not hard retract
neck stays quiet
How often to do this
Do the 3-drill sequence 3 to 5 days per week for one week.
Look for small, real wins:
less shrugging with reach
More awareness of the musculature of the sides of your ribcage
easier overhead motion
more upper back width without trying
quieter neck during breathing
more natural rib expansion
Consistency beats intensity here.
What you may notice in your breathing
After a few rounds of these drills, many people notice their breath changes without trying to “do breathing exercises.”
Common shifts include:
the neck feels quieter on the inhale
the upper back feels wider and more supported
it becomes easier to feel expansion into the back and side ribs
the exhale feels longer and less forced
That is not because you “breathed better.” It is because your ribcage and shoulder blade have more support, so breathing takes less effort.
If you want the full 360 breathing breakdown, you can read it here: 360 Breathing: The Key to Optimal Pressure Management and Pain-Free Movement
If you want help integrating this into real movement
If you can feel serratus support here but lose it when you stand up, reach, or move, you’re not doing anything wrong. You just need progressions.
My 360 Breathing Course shows you how to create space and keep expansion as you change positions and integrate it under load.
