Serratus anterior usually gets filed under shoulder muscle. It’s the broad, fan-shaped muscle that wraps around your rib cage and attaches to your shoulder blade, and it’s typically talked about in the context of pressing and reaching. What gets missed is that this same muscle plays a direct role in how well your rib cage moves and after pregnancy, when your rib cage has flared and widened to make room for your baby, that role matters far more than most people realise.

Many women find themselves breathing in a shallow, vertical pattern well into postpartum — chest rising, ribs staying relatively still — without realising that full, three-dimensional breath is something they need to actively restore. Serratus anterior is one of the key muscles that helps restore it.

This matters more than it might seem. Your breath isn’t separate from your core. It’s the foundation of it.

The rib cage, the diaphragm and why serratus anterior matters here

Your diaphragm needs your rib cage to move well in order to do its job properly. When you inhale, your ribs should expand outward and slightly backward, giving your diaphragm room to descend fully. If your ribs are stuck in a flared, elevated postpartum position, that expansion is limited and so is the quality of every breath you take.

Because of where it attaches, serratus anterior plays a role in positioning and stabilising the rib cage itself, which gives it a direct line to how well you breathe. When it’s doing its job, it helps anchor the ribs in a position that allows for full lateral and posterior expansion on the inhale. When it’s underused (which is common postpartum, when overhead and reaching patterns often drop out of daily life for a while), the rib cage can lose some of that support, and breath mechanics stay limited.

Why this matters for your core

Full, well-mechanised breathing is what allows you to manage intra-abdominal pressure (the pressure inside your trunk that your core canister — diaphragm, pelvic floor, deep abdominals and back muscles — is built to regulate). If your rib cage isn’t moving well and your breath is staying shallow and chest dominant, that pressure has fewer places to go, and your core canister can’t do its job as effectively.

This is part of why cueing like “brace your core” or “zip up from the bottom” often falls flat without addressing what’s happening above it. You can’t manage pressure well through a system that isn’t breathing well. Restoring rib mobility and serratus anterior function isn’t a detour from core work, instead it’s part of the foundation it’s built on.

Building it back: breath, mobility, then load

The exercises below are sequenced deliberately: starting with breath in a supported position, moving into mobility work that reintroduces movement through the rib cage and shoulder blade, and finishing with exercises that integrate breath into loaded, strengthbuilding patterns.

Foundational breath

90/90 breathing with band serratus reach — This position puts your hips and rib cage into a supported stacked position, making it easier to feel where your breath is actually going. The added band reach asks serratus anterior to work at the same time as your ribs expand, so instead of training breath and shoulder mechanics separately, you’re teaching your body to coordinate them from the start. For many women postpartum, this is a great position for them to feel their ribs move both laterally and posteriorly vs just directly into chest or belly.

Bear plank breathing with band resist — Loading the position through hands and knees changes the demand on your rib cage compared to lying down — you now have to expand your ribs against gravity and against light band resistance at the same time. This helps build the strength and awareness to keep breathing well even when your trunk is under some tension, which is a closer approximation to how you’ll need to breathe during actual strength work later in the progression.

Mobility

Alternating serratus slides against wall — This exercise reintroduce active, controlled movement through the shoulder blade against the rib cage, which is exactly the mechanism serratus anterior relies on to do its job. If overhead and reaching patterns have dropped out of your daily life since having a baby (which is extremely common), this is where that range starts coming back — gradually, and without load.

Integration (breath and load)

Serratus punch with kettlebell and iso adductors — Here, the reaching pattern is loaded with real resistance while an isometric adductor hold adds tension elsewhere in the body. This combination asks your core canister to manage intra-abdominal pressure under whole-body demand, not just during a single isolated movement — which is a much closer reflection of how your core actually gets used day to day, whether that’s carrying a car seat or getting up off the floor.

Forearm bear plank with serratus press — Building on the earlier bear plank breathing work, this version adds an active serratus press, asking you to maintain rib and pelvic positioning through an anti-extension core pattern while your shoulder blade moves against resistance. It’s a strong test of whether your breath mechanics hold up once real strength demands are layered on top.

Inline cable press with rotation and reach — Trunk rotation adds a dimension that most of the earlier exercises don’t include, and it’s closer to how your body actually moves in daily life — reaching, twisting, lifting. This exercise asks your rib cage and core canister to manage pressure through a rotational plane, while still keeping the breath and serratus engagement you’ve built through the earlier stages of the progression.

Rotational landmine press — As the most advanced exercise in this sequence, the landmine press combines rotation, pressing, and full body loading in a single pattern. It requires your rib cage, shoulder, and core canister to work together seamlessly under real strength demand, making it a genuine test and a strength-building expression of everything the earlier stages have built.

Where this fits in your training

If you’re rebuilding strength postpartum, breath mechanics and rib mobility aren’t a separate box to tick before the real training starts — they’re part of it. This is exactly the kind of foundation we build into Return to Strength, where breath, pressure management, and rib cage mobility are trained alongside the strength work itself, not as a prerequisite to it.