Building a strong core starts with training the right functions: resisting extension, resisting lateral flexion, resisting rotation, and transferring force through the hips. Crunches train none of those things effectively. The exercises that actually build core strength look nothing like what most gym goers do for "ab work."
I've watched thousands of training sessions across 13 years, and the pattern is always the same. Someone complains about low back pain or a weak midsection. I ask about their core training. They tell me they do 3 sets of crunches and some leg raises after every workout. That's not core training. That's spinal flexion training, and it's a tiny sliver of what the core actually does.
What the Core Actually Is
The core is not your six-pack muscles. It's a 360-degree muscular cylinder that wraps around your trunk, from your diaphragm at the top to your pelvic floor at the bottom, with layers of muscle all the way around.
The key players:
- Transverse abdominis (TVA): The deepest abdominal layer. Wraps horizontally around the trunk like a corset. Creates intra-abdominal pressure, which is the primary spinal stabilizer during heavy lifting.
- Internal and external obliques: The diagonal layers. Control rotation and lateral flexion. Often undertrained because crunches don't target them.
- Rectus abdominis: The six-pack muscle. Controls spinal flexion. The one everyone trains. The one that matters least for actual core function.
- Erector spinae: The muscles running along your spine. Control spinal extension and lateral flexion. Critical for deadlifts, squats, and staying upright under load.
- Multifidus: Deep spinal stabilizers. Fire before your limbs move to pre-stiffen the spine. Often the first thing to shut down after low back injury.
- Glutes: Technically not "core" in the traditional sense, but they anchor the pelvis and are essential for force transfer between the lower body and spine.
- Pelvic floor: The base of the cylinder. Works with the TVA and diaphragm to create intra-abdominal pressure. Rarely trained consciously but critical, especially for women.
When all of these muscles work together as a unit, the spine stays rigid under load, force transfers efficiently from the legs through the trunk to the arms, and injury risk drops dramatically. When one piece is weak or doesn't fire at the right time, the whole system compensates. Usually badly. Usually the low back pays the price.
Research from Dr. Stuart McGill at the University of Waterloo, who spent decades studying spinal mechanics, established that core stability training outperforms core strengthening exercises for reducing low back pain and improving athletic performance. His Big Three (McGill curl-up, side plank, bird dog) are all stability-based, not flexion-based.
The key insight: the spine is most stable when it resists movement, not when it produces it. A core strong enough to hold a neutral position under load is far more valuable than a core that can do 100 crunches.
Why Crunches Are the Wrong Tool
Crunches are not inherently dangerous. But they are severely limited and overused. Here's the actual problem.
Crunches train spinal flexion. That is one thing the core does, and it's a relatively unimportant one for real-world strength and injury prevention. Meanwhile, they completely ignore anti-extension, anti-rotation, anti-lateral flexion, and hip transfer, which are the four functions that actually matter when you're squatting, deadlifting, carrying groceries, or playing with your kids.
Crunches also repeatedly load the lumbar discs in a flexed position under compression. For people with healthy spines and no history of disc issues, this is not a serious concern in moderate doses. For people with any low back history, including the majority of adults, repeated lumbar flexion under load is exactly the mechanism that aggravates disc herniation. It's not a risk worth taking when better exercises exist.
The deeper issue is that crunches train the rectus abdominis in isolation. Real core function is never isolated. Every time you lift something heavy, your entire trunk fires as a unit. Training one muscle in one plane of motion does not prepare the core for the 3D demands of real movement.
The 4 Functions of the Core
This is CoachCMFit's framework for building a complete core program. Every function needs to be trained, and most people only ever train one.
1. Anti-Extension
Resisting the extension of the lumbar spine under load. This is what keeps your lower back from collapsing during a plank, a push-up, or an overhead press. The TVA and rectus abdominis work here.
Best exercises: Dead bug, ab wheel rollout, plank (correctly executed), push-up hold, RKC plank. The dead bug is the single best anti-extension exercise for most people because it trains the TVA directly, demands coordination between the arms and legs, and has essentially zero injury risk.
2. Anti-Lateral Flexion
Resisting side-bending. This is what keeps your torso from collapsing sideways when you carry a single heavy bag, do a single-leg exercise, or work in a split stance. The obliques and quadratus lumborum (QL) handle this.
Best exercises: Side plank, suitcase carry (heavy dumbbell in one hand, walk for distance), Copenhagen plank, single-arm farmer's carry. The suitcase carry is criminally underrated. Walking with a heavy dumbbell in one hand while keeping your torso perfectly upright is brutally hard and highly functional.
3. Anti-Rotation
Resisting rotation of the trunk. This is what keeps your hips and shoulders squared up during single-arm and single-leg movements. The obliques and multifidus dominate here.
Best exercises: Pallof press (cable or band pressing straight out from a kneeling or standing position), single-arm dumbbell row (requires anti-rotation to prevent twisting), half-kneeling single-arm press. The Pallof press is the go-to for this function, simple to learn and infinitely scalable.
4. Hip Transfer (Force Transfer)
The ability to transfer force from the lower body through the trunk to the upper body. This is what makes your deadlift, squat, and row actually work. Without it, you're a disconnected collection of body parts instead of a coordinated system.
Best exercises: Deadlift, barbell squat, hip thrust, hip hinge patterns. All compound lifts train force transfer, which is why compound training builds a stronger core than isolated ab work. The core doesn't function independently. It functions in service of bigger movements.
CoachCMFit's Warm-Up Core Activation Protocol
Every CoachCMFit training session starts with a structured warm-up that includes a dedicated core activation phase. This is not optional filler. The research from McGill and others is clear that pre-activating the deep stabilizers before heavy compound work significantly reduces injury risk and improves performance under load.
Core Activation Phase (Every Session)
Step 1: Diaphragmatic breathing (90-90 position). Lie on your back, hips and knees at 90 degrees, feet on the wall. Breathe into your belly, feeling the lower back press into the floor on the exhale. 5 slow breaths. This activates the TVA and pelvic floor before anything else fires.
Step 2: Dead bug (3 reps per side). Lying on your back, arms extended overhead, legs at 90 degrees. Slowly lower one arm and the opposite leg toward the floor while pressing your lower back flat. Return and repeat. Exhale on the way down.
Step 3: McGill bird dog (3 reps per side). On hands and knees, extend one arm and the opposite leg while maintaining a completely neutral spine. Hold 3 seconds, return. This is the clearest window into how well the deep stabilizers are firing.
Step 4: Side plank (20 seconds per side). Full or modified (knee on floor). Creates the lateral stiffness needed for squats and deadlifts where anti-lateral flexion demand is high.
This takes about 4-5 minutes. The difference in how your lifts feel after running this protocol versus jumping straight into working sets is significant, especially on heavy lower body days.
How a Strong Core Improves Every Lift
This is the part people miss. Core training is not a separate goal from strength training. It's a prerequisite for it.
When you squat, the core must resist flexion of the lumbar spine under the weight of the barbell. A weak core means your lower back rounds at the bottom, which shifts the load away from the quads and hips and onto the spinal column. Your squat gets weaker and your back gets stressed.
When you deadlift, the core must create enough intra-abdominal pressure to keep the spine rigid as you pull the bar from the floor. Without that stiffness, the force leaks. The bar feels heavier. Form breaks down at weights you should be handling comfortably.
On the overhead press, anti-extension strength is what prevents the lower back from hyperextending as the weight gets heavy. On rows, anti-rotation strength is what keeps your torso from twisting with each rep. These are not peripheral concerns. They are the limiting factor in how much weight you can lift safely and effectively.
Training the core as a unit, across all four functions, removes that limiting factor. Every major lift gets stronger. Fixing anterior pelvic tilt, which is directly connected to weak core stabilizers, also unlocks better movement quality across the board.
A Complete Core Training Block
| Function | Exercise | Sets x Reps | Notes |
|---|---|---|---|
| Anti-extension | Dead bug | 3 x 6/side | Slow and controlled, exhale each rep |
| Anti-lateral flexion | Side plank | 3 x 20-30 sec/side | Full or modified (knee down) |
| Anti-rotation | Pallof press | 3 x 8/side | Cable or band at chest height |
| Hip transfer | Hip thrust or deadlift | Per main program | Already in your compound training |
| Anti-extension (loaded) | Ab wheel rollout | 3 x 6-8 | From knees, advanced: from toes |
| Anti-lateral flexion (loaded) | Suitcase carry | 3 x 30m/side | Heavy dumbbell, torso perfectly upright |
- Run the CoachCMFit core activation warm-up before every training session (4-5 min).
- Add 2-3 direct core exercises at the end of 2-3 sessions per week, not every session.
- Pick one exercise from at least two different function categories each session.
- Prioritize quality over reps. A perfect 6-rep set of dead bugs beats 20 sloppy ones.
- Progress by adding duration (planks), resistance (Pallof press load, ab wheel from toes), or range of motion (deeper rollout).
- Let your compound lifts do the heavy lifting for hip transfer. Squats and deadlifts train this better than any isolation core exercise.
The core truth: A six-pack is a nutrition outcome. Core strength is a training outcome. You can have a strong core at any body fat percentage, and you can have visible abs with a weak core. Train for function. The aesthetics follow from consistent training and smart nutrition, not from doing more crunches.
CoachCMFit builds core activation into every client's warm-up and programs specific core exercises based on the client's weak points and goals. If you're dealing with low back pain, poor posture, or a stalling squat and deadlift, the core is almost always part of the answer. Fixing muscle imbalances usually starts with the core, because everything in the kinetic chain connects to it.