Deep Core Training: The Muscles Under Your Six Pack
Your six pack sits on top of a layer of deeper muscles that hold your trunk together. Here's what they do and how to train them without wasting time.
Deep core training means working the muscles underneath your six pack, mainly the transverse abdominis, internal obliques, multifidus, diaphragm and pelvic floor, which stabilise your spine and control pressure inside your trunk. You train them best with slow, controlled exercises where the goal is to keep your torso still: dead bugs, hollow holds, bird dogs, Pallof presses and loaded carries. They won't change how your abs look much on their own, but they make everything else you do in the gym more solid.
Here's what those muscles are, what deep core training can and can't do, and a simple routine you can add to your week.
What "deep core" actually means
When people say "core," they often mean the rectus abdominis, the six-pack muscle. That's the outermost layer. Underneath it is a group of muscles that work together like a pressurised cylinder around your spine.
| Muscle | Where it is | What it does |
|---|---|---|
| Transverse abdominis (TVA) | Deepest ab layer, wraps around like a belt | Tightens the waist, helps create intra-abdominal pressure |
| Internal obliques | Under the external obliques | Rotation, side bending, bracing |
| Multifidus | Small muscles along the spine | Segment-by-segment spinal stability |
| Diaphragm | Top of the cylinder | Breathing and pressure control |
| Pelvic floor | Bottom of the cylinder | Supports organs, contributes to pressure and continence |
These muscles rarely act alone. When you brace before a heavy lift, they tighten together with your outer abs to stiffen your trunk. That stiffness lets force pass from your legs to your arms without your spine bending where it shouldn't.
What deep core training can and can't do
It helps to be clear about expectations.
What it can do:
- Improve your ability to brace under load, which helps with squats, deadlifts and carries. Our guide to breathing and core bracing covers the technique side.
- Give you better control of your pelvis and ribcage, which makes leg raises, rollouts and planks feel more effective.
- Help your waist look a little tighter at rest for some people, because the TVA influences how much your stomach pushes out.
What it can't do:
- Burn belly fat. No exercise does that locally. See can you spot-reduce belly fat for why.
- Fix back pain on its own. Core work is often part of rehab, but back pain has many causes. If you have pain, see a doctor or physical therapist for a proper assessment.
- Replace your regular ab training. You still need loaded work for the visible muscles.
The best deep core exercises
The common thread here is control. You're not chasing a burn. You're trying to keep your spine and pelvis still while your limbs move or while something tries to pull you out of position.
Dead bug
Lie on your back, arms up, knees bent at 90 degrees over your hips. Press your lower back gently into the floor and slowly extend one arm and the opposite leg. Return and switch. If your back arches off the floor, shorten the range. The dead bug guide explains the subtle mistakes.
Hollow body hold
A gymnastics staple that trains the whole front of your trunk to resist arching. Start with knees tucked and progress to straight legs. More on that in the hollow body hold breakdown.
Bird dog
On hands and knees, extend one arm and the opposite leg while keeping your hips level. It's a good way to train the multifidus and glutes with your spine in neutral. Move slowly enough that a cup balanced on your lower back wouldn't fall.
Pallof press
Stand side-on to a cable or band, hold the handle at your chest and press it straight out. The cable tries to twist you. Your job is to not let it. This is deep core and oblique work in one move.
Suitcase carry
Hold a heavy dumbbell in one hand and walk. Staying upright against the weight demands a lot from the obliques and lateral stabilisers. The suitcase carry is one of the most practical core exercises there is.
Stomach vacuum
Exhale fully and draw your belly button toward your spine, holding for 10-20 seconds while breathing shallowly. It's a direct TVA drill. The evidence for big visual changes is limited, but it's a reasonable way to learn how to switch the TVA on. See our page on the stomach vacuum.
A 15-minute deep core routine
Do this two or three times a week, either as a warm-up before lifting (use the lower end of each range) or as a standalone session.
- Dead bug: 3 sets x 6-8 slow reps per side
- Bird dog: 2 sets x 6 reps per side, 3-second hold at full extension
- Hollow body hold: 3 sets x 20-30 seconds
- Pallof press: 2 sets x 10 reps per side, 2-second hold
- Suitcase carry: 2 sets x 30 m per side
Rest 30-60 seconds between sets. A plank timer is handy for the holds, and the free plank timer works for any timed exercise.
How to progress deep core exercises
Because these moves aren't about lifting heavy, progression looks a little different:
- Longer lever. Straighten your legs in the dead bug or hollow hold.
- Slower tempo. Take 4 seconds to extend and 4 to return.
- More resistance. Use a heavier cable on the Pallof press or a heavier dumbbell on carries.
- Less stability. Lift the supporting knee off the floor slightly in a bird dog.
- Longer holds. Add 5 seconds to each hold once all sets feel controlled.
Only progress when you can keep the position perfect. A shaky hollow hold with your back arched is training the wrong thing.
Breathing is part of it
Your diaphragm is the top of the core cylinder, so how you breathe matters. During slow control drills, try to breathe low into your belly and sides while keeping your lower back in position. During heavy lifts, take a big breath, brace around it and hold or exhale slowly through the hardest part. Holding your breath on every rep of a light dead bug misses the point.
Special cases
If you're pregnant, recently postpartum or think you may have diastasis recti, deep core work is often part of recovery, but the details matter and should be guided by a doctor or pelvic health physical therapist. Our article on diastasis recti and ab training explains the general picture.
The same goes for pelvic floor symptoms like leaking or heaviness. Don't just push through with more core exercises. Get it checked.
Where AbShred fits
Deep core strength is hard to judge in the mirror. AbShred, an iPhone app that's coming soon, scores a Deep Core zone alongside Upper Abs, Lower Abs, Obliques, Symmetry and V-Taper from a single photo, and builds your weekly plan around whichever zone scores lowest. It's an AI estimate meant for motivation, not a clinical assessment. You can join the waitlist at abshred.com.
FAQ
What is the deep core?
It's the inner layer of trunk muscles: the transverse abdominis, internal obliques, multifidus, diaphragm and pelvic floor. They work together to stabilise your spine and manage pressure inside your abdomen.
Does deep core training flatten your stomach?
It can help your waist look a little tighter at rest for some people, but it won't remove fat. A flatter stomach mostly comes from losing body fat, along with factors like bloating and posture.
How often should I train my deep core?
Two or three short sessions a week is enough for most people. You can also use a few deep core drills as a warm-up before lifting.
Are planks deep core exercises?
Planks train the deep core along with the outer abs. They're useful, but dead bugs, hollow holds and Pallof presses often teach better control because it's harder to cheat the position.
Can deep core training help back pain?
It's often part of a rehab plan, but it isn't a guaranteed fix. Back pain has many causes, so get assessed by a doctor or physical therapist before using exercise to treat it.