The postpartum core narrative tends to focus almost entirely on the lower abs. But the lower abs are only one part of a much larger system. Real core function depends on the entire unit working together: the diaphragm, pelvic floor, deep abdominals, and obliques, all coordinating to manage pressure through the trunk. Train one piece in isolation and the rest of the system doesn’t automatically follow.

The obliques are a central part of that system, and they’re worth understanding on their own terms.

What the Obliques Do

The internal and external obliques aren’t just rotators, and they’re not just “side abs.” Their primary early job postpartum is anti-rotation: resisting unwanted movement through the trunk before they’re ever asked to create it. Rotation comes later, once that control is established.

Beyond anti-rotation and rotation, the obliques have a few other jobs worth knowing about:

• Rib-to-pelvis stacking — helping keep the rib cage positioned over the pelvis rather than flared or shifted forward.
• Forced exhalation and breathing mechanics — the internal obliques in particular play a role in actively pushing air out, tying oblique function directly to breath.

When the Internal Obliques Underperform

Excess Lumbar Extension

When the obliques aren’t doing their share of anterior wall tension, the lumbar spine often ends up compensating by sitting in more extension than it should to maintain posture and pelvic position.

Rib Flare Posture

Underactive obliques struggle to hold the rib cage stacked over the pelvis, so the front ribs can sit lifted and flared rather than settled—a visible sign the rib-to-pelvis connection isn’t being maintained.

Poor Rotational Control

Since the obliques are the primary anti-rotation muscles, underrecruitment shows up as difficulty resisting rotational forces during everyday movement—twisting to reach something, shifting weight, or carrying asymmetrical loads.

Low Back Pain When Lifting

Without adequate oblique contribution to trunk stability, the lumbar spine and surrounding structures take on more load during lifting than they’re designed to manage alone, which can present as discomfort or pain.

Pelvic Instability

The obliques work alongside the pelvic floor and deep core as part of the same pressure system. When they’re underperforming, the pelvis can lose some of its stability during movement, particularly under load or on one leg.

Reduced Force Transfer

The obliques are a key link in transferring force between the upper and lower body—through the oblique sling connecting to the opposite lat and adductor. Underrecruitment weakens that transfer, making movements like throwing, swinging, or carrying feel less powerful or coordinated.

When the Internal Obliques Become Overactive and Gripped

Underrecruitment isn’t the only way this system goes wrong. Sometimes the internal obliques go the other direction entirely—gripping and overworking rather than sitting quiet.

Lateral Trunk Tightness

An overactive internal oblique can sit in a near-constant state of tension, particularly on one side, which often feels like tightness or restriction through the waist that doesn’t respond to stretching alone.

Asymmetrical Rib Position

Because the obliques help position the rib cage, one side gripping more than the other can pull the ribs into an uneven or rotated resting position rather than a stacked, neutral one.

Restricted Breathing

The internal obliques play a role in exhalation. When they’re gripped rather than working through a full range, that same tension can limit how freely the rib cage expands and releases with each breath, making breathing feel shallow or effortful.

Why This Happens

Gripping often develops as a compensation strategy—the body finding stability through tension when the deeper pressure system (diaphragm, pelvic floor, deep abdominals) isn’t coordinating efficiently. It can also show up as a holdover from pregnancy posture, or from bracing patterns like the “zip up” cue used without the underlying pressure management foundation to support it.

This pattern needs a different starting point than loading: 90/90 breathing, rib mobility work, controlled thoracic rotation, and soft tissue work with breath integration, before any loaded rotation is introduced. That’s a progression worth its own post.

Why rotation matters postpartum

Rotation puts a different demand on the pressure system than flexion or extension does. Instead of managing pressure through a single plane, the trunk has to coordinate pressure while the ribs, spine, and pelvis move out of alignment with each other and back again. For a system that’s already relearning rib-to-pelvis stacking and breath coordination, this is a meaningful step up in difficulty—which is exactly why it deserves deliberate, staged training rather than being left out altogether.

This is also where diastasis recti comes in. Rotation isn’t inherently harmful to the linea alba. The focus postpartum is building a reliable pressure strategy so rotation is trained deliberately, not avoided altogether.

There’s a thoracic spine link here too. The same rib-to-pelvis stacking discussed earlier depends partly on available rotation through the thoracic spine. When that rotation is limited, the body tends to compensate elsewhere—often through the lumbar spine or SI joint, areas that weren’t designed to pick up the slack.

Trained well, rotation strengthens the same system this whole post has been building toward: obliques that can hold, resist, and eventually produce rotation, coordinated with breath and pressure management rather than working around it.

The Progression: Building Well-Rounded Oblique Strength

Rebuilding oblique function postpartum isn’t a single-track path to rotation. It’s a progression through the different demands the obliques are built to handle—starting with control, moving through breath-integrated coordination, and finishing with varied loading strategies.

Stage 1: Anti-Rotation Control

The foundation. These exercises train the trunk to resist an outside rotational force, building the stability everything else is built on.

• Pallof press
• Deadbug with iso diagonal pulldown

Stage 2: Controlled Rotation with Breath-Integrated Core Work

This stage introduces movement through rotation while keeping breath and pressure management coordinated throughout. Alongside the rotational demand, each of these also carries an anti-rotation and core-control component.

• Short lever side plank with rotation
• ½ kneeling cable chop
• ½ kneeling cable lift

Stage 3: Advanced Loading Strategies

The final stage loads the trunk through several different demands: producing controlled rotation, resisting lateral flexion, and managing asymmetrical load.

• Tall kneeling band side bend — lateral flexion
• Offset carry — anti-lateral flexion under load

The Takeaway

The obliques are more than side abs, and they’re more than rotators. They stack the ribs over the pelvis, support exhalation, resist force, and eventually produce it—all while coordinating with breath and pressure management. Training them well postpartum means building all of that back deliberately, in the right order, rather than loading a system that isn’t ready yet.

Where This Fits in Your Training

This progression is built into Return to Strength, structured so oblique function develops through every demand it’s meant to handle—anti-rotation, breath-integrated rotation, and varied loading—rather than jumping straight to exercises that only train one piece of the system.

Try your first 7 days free of my postpartum program HERE.