You Cannot Out-Crunch Your Way Out of a Weak Core

I had a client come in last month with three years of nagging low back pain. He had been training hard the entire time. Planks every morning. A hundred crunches at the end of every workout. Side bends, leg raises, a rotating cast of ab-roller variations. His midsection looked strong from across the room, and he still could not sit through a movie without his back lighting up.

When I walked him through a basic inner unit assessment, the picture got clearer fast. He could brace. He could crunch. What he could not do — and what almost no one in chronic pain can do when I first meet them — was draw his transversus abdominis in independently of the rest of his abdominal wall, while breathing into his diaphragm, without his ribs flaring or his pelvis tucking. The "core" he had been training for three years was not the one his spine actually needed.

This is one of the most common patterns I see, and it is also one of the most fixable. But it requires you to stop and rewire something most people have never been taught.

In CHEK's framework, your core is not one thing. It is two functionally distinct units under separate neurological control — a distinction first mapped clinically by Bogduk and Twomey in 1987, and then developed in detail by Richardson, Jull, Hodges, and Hides in their landmark spinal stabilization research at the University of Queensland.

The inner unit is the deep, segmental system: the transversus abdominis, the posterior fibers of the internal oblique, the multifidus along your spine, the pelvic floor, and — critically — the diaphragm. These muscles fire in low-level tonic patterns. Their job is joint stiffness. Stability. They are the small guy wires holding the mast of your spine upright in what Paul Chek calls the pirate ship model — a mast (your vertebrae) can never stand against the wind if the small segmental wires are loose, no matter how thick the large outer wires are.

The outer unit is the four sling systems — deep longitudinal, posterior oblique, anterior oblique, and lateral — that ride on top of the inner unit. These are your prime movers. Your rectus abdominis, your lats, your glutes, your obliques in their phasic role. These are the muscles a crunch trains. They are also the muscles that, when overdeveloped relative to the inner unit, will quite literally pull your ribcage down, drag your head forward, and load the very joints they were supposed to protect.

This is not theory. In Paul Chek's clinical observations across his career, roughly 98 percent of clients presenting with back pain had a weak lower abdominal wall and a non-firing transversus abdominis. The other 2 percent had something else entirely going on. The pattern is that consistent.

Here is the part most people skip, and the part that changes everything once you understand it: your diaphragm is not just a breathing muscle. It is one of the four walls of your inner unit. When it co-activates with your transversus abdominis below, your pelvic floor at the base, and your multifidus along the spine, those four walls compress and encapsulate your abdominal contents. That compression is what creates intra-abdominal pressure — the thing your spine actually leans against when you pick something up, take a step, or stand up out of a chair.

If you cannot breathe down into your belly without your shoulders rising and your neck tensing, you are not loading that pressure system. You are using accessory respiration muscles to suck air into the top of your lungs while your inner unit stays offline. Do this for years and the downstream picture becomes predictable: forward head posture, depressed first rib angle, locked-down upper traps, a pelvic floor that does not know how to drop, and a spine that has no platform from which to generate force. So you reach for the crunch. And the crunch shortens your rectus, pulls your ribs down further, and the cycle deepens.

This is what I mean when I tell clients: you cannot out-crunch your way out of a weak core. The crunch is the wrong tool. It is training the wrong tissue, in the wrong direction, in the wrong neurological pattern.

Before anyone in my coaching program does a single loaded movement, we re-pattern three things in this specific order.

Lying supine, one hand on the lower belly, one hand on the chest. The goal is a slow inhale that expands the lower hand without lifting the upper hand. Four seconds in through the nose, eight seconds out through the lips. No shoulder rise. No neck strain. If the upper hand moves first, we stay here until it does not. For some people this takes two sessions. For some it takes two months. The body has to remember how to descend the diaphragm before anything else makes sense.

Quadruped position, spine in neutral. Inhale and let the belly drop softly toward the floor. Exhale fully and draw the navel up toward the spine without moving the back. Hold ten seconds. Repeat ten times for one set, working up to three sets. The spine does not move. The breath does not stop. The big abdominals do not bunch. This is harder than it sounds and it is the single highest-leverage drill I teach.

Horse Stance Vertical first — opposite hand and knee lift only enough to slip a sheet of paper underneath, held in perfect alignment for ten seconds. Then Horse Stance Horizontal — opposite arm and leg fully extended, dowel rod balanced along the spine, no pelvic tilt. Then the Horse Stance Alphabet — drawing letters with the extended leg, with the inner unit holding everything else perfectly still. These three exercises rebuild the multifidus and TVA in the same patterns they are supposed to fire in real life.

Notice what is not in this list. No planks. No crunches. No side bends. Not yet. Not until the inner unit is actually online and the breath is patterned, because layering load on top of a leaky stability system is exactly how chronic pain compounds.

Inner unit dysfunction is not a binary. It is a spectrum, and almost everyone in modern life is somewhere on it. Sit at a desk for years and your diaphragm shortens. Wear restrictive clothing and your transversus stops firing reflexively. Strap on a weight belt for every heavy lift and your body starts pushing outward into the belt instead of drawing the navel inward toward the spine — which, as Paul Chek pointed out decades ago, is a beautiful way to teach your nervous system that it does not need its own internal weight belt anymore.

The good news is that the inner unit is built to be retrained. The diaphragm responds to focused breathwork within days. The transversus rebuilds reflex activation within weeks of consistent isolation drills. The multifidus relearns its segmental job once it stops being drowned out by an overpowered rectus abdominis. I have watched clients move from "I cannot bend over without bracing" to "I forgot what back pain felt like" inside of a season — not by training harder, but by training the right system first.

If you have been doing the work and the back pain is still there, the work is not wrong. The order is. Get your breath right. Get your inner unit online. Then layer the strength.

The inner unit assessment is genuinely subtle, and most people self-correct in the wrong direction when they try to do it solo. They brace harder when they should be softening. They suck the belly in flat when they should be drawing the navel up toward the spine. They hold their breath instead of breathing through the contraction. Without feedback, the drill becomes another way to reinforce the same pattern that got them here.

If you have been chasing the same nagging back, hip, or shoulder pattern for more than a few months — or if you suspect your "strong core" is actually masking a stability deficit — that is the moment to get a trained eye on it. You are not stuck with the pattern you have. You are just one neurological retraining away from a core that actually does its job.