The Diaphragm: Breathing, Stability and the DNSLens

Your diaphragm has two jobs, and most people only know about one of them.
Ask anyone what the diaphragm does and you’ll hear “breathing”. Correct, but incomplete. The same muscle also helps pressurise your trunk so your spine has a stable base to move from. It does both, often at the same time, every time you lift, reach, run or carry.

That dual role is the focus of this piece. We’ll look at it through the lens of Dynamic Neuromuscular Stabilisation (DNS), an approach built on how babies learn to move. Then we’ll be honest about what the evidence does and doesn’t support, because that part usually gets left out.

What the diaphragm actually is

The diaphragm is a dome-shaped sheet of muscle that separates your chest from your abdomen. Picture an open parachute sitting under your lungs and heart.
Its attachments explain a lot about why it matters beyond breathing:

What the diaphragm actually is

The diaphragm is a dome-shaped sheet of muscle separating your chest from your abdomen — picture an open parachute sitting beneath your lungs and heart.
Its attachments help explain why it matters beyond breathing:

• Front: the back of the sternum (xiphoid process)
• Sides: the inner surface of the lower six ribs
• Back: the lumbar spine, via two tendinous legs called the crura
• Centre: a flat central tendon that the muscle fibres pull on

That last attachment at the back is the one people forget. Your diaphragm is physically anchored to your lower spine. It sits directly above your pelvic floor and is wrapped by your deep abdominal wall. Together these form the walls, roof and floor of a pressurised container: your trunk.
It is driven by the phrenic nerve, which exits the neck at C3–C5. Breathing is automatic, but you can also override it voluntarily. That makes the diaphragm one of the few muscles run by both your brainstem on autopilot and your conscious control.

Job one: breathing

The diaphragm is your primary muscle of inhalation. At rest, it does most of the work of each breath.
When it contracts, the dome flattens and moves down. That increases the volume of your chest, pressure in the lungs drops, and air flows in. When it relaxes, the dome rises again and you exhale, mostly passively.
Here’s the part that links to job two. As the dome descends, it pushes down on your abdominal contents. Those contents have to go somewhere. If the abdominal wall and pelvic floor allow some give but also provide some resistance, pressure inside the abdomen rises. That pressure is the starting point for stability.
When the diaphragm isn’t doing its share, the neck and upper chest muscles tend to pick up the slack. Scalenes, upper trapezius and sternocleidomastoid are built as backup breathing muscles, not primary ones. Using them for every breath, all day, is a pattern worth noticing.

Job two: stability

The diaphragm also contracts to stabilise your trunk, and it can do this while you keep breathing.

The clearest early evidence came from Australian researchers Paul Hodges and Simon Gandevia. When people made repetitive arm movements, the diaphragm didn’t just switch on and off with each breath. It stayed active through the whole breathing cycle, including the out-breath, with extra bursts timed to the arm movement (Hodges & Gandevia, 2000a). That tonic activity raised pressure inside the abdomen (Hodges & Gandevia, 2000b).

Why does that pressure matter? Intra-abdominal pressure (IAP) makes the lumbar spine stiffer and better controlled under load, even without help from the abdominal or back muscles (Hodges et al., 2005). Think of a sealed can of soft drink: hard to crush while it’s full and pressurised, easy once it’s opened..

The catch: one muscle, two jobs

When breathing demand goes up, breathing wins. In a follow-up study, the diaphragm’s postural activity dropped off or disappeared once breathing demand was pushed up by rebreathing CO2 (Hodges, Heijnen & Gandevia, 2001).

That makes sense from a survival standpoint. Oxygen comes first; stabilising your spine for a reach comes second. But it raises a practical question for anyone who lifts, runs, or lives with a respiratory condition: what’s picking up the stabilising job when the diaphragm is busy?

There are hints that this matters beyond the lab. A large survey of Australian women found breathing and continence disorders were more strongly associated with back pain than obesity or physical activity levels (Smith, Russell & Hodges, 2006). That is an association, not proof of cause. It is still a strong signal that breathing, the pelvic floor and the back are not separate systems.

The DNS lens: what babies already know

Dynamic Neuromuscular Stabilisation starts from a simple premise: the way a healthy infant learns to stabilise is the template for how adults should.

DNS comes out of the Prague School of rehabilitation (Vojta, Janda, Lewit) and was developed by Czech physiotherapist Pavel Kolář. It draws on developmental kinesiology, the study of how movement emerges in the first year of life (Frank, Kobesova & Kolář, 2013).

The idea is that these early patterns are largely driven by the maturing nervous system, not taught. No one coaches a baby to hold their head up or roll. The central nervous system unfolds a sequence, and the trunk learns to stabilise before the limbs learn to do skilled work.

The three-month-old

Watch a healthy three-month-old lying on their back with legs lifted. Their spine is long and neutral. Their chest sits low rather than lifted. Their belly is rounded all the way around, not just at the front.

In DNS terms, this is ideal trunk stabilisation. The diaphragm sits roughly parallel to the pelvic floor. When it descends, pressure spreads evenly through the whole cylinder: front, sides and back. The abdominal wall works against that pressure rather than sucking in or pushing out.

What changes in adults

Many adults drift from that pattern. A common version is what DNS practitioners call the “open scissors” posture:

• Lower ribs flared up and forward
• Pelvis tipped forward, low back arched
• Diaphragm and pelvic floor no longer facing each other Breathing driven by the upper chest and neck
• Back extensor muscles doing more of the stabilising work

In this position, the diaphragm and pelvic floor can’t form an efficient pressure seal. The system still works, but it may lean on muscles that weren’t designed to carry that load all day.

How this differs from “engage your core”

DNS is not about sucking your belly button to your spine. It’s also not maximal bracing. The target is a coordinated pattern: diaphragm descends, the lower trunk widens in every direction, and the abdominal wall resists that widening. The emphasis is on the pattern and its timing, and on getting it into real movement, not just lying on a mat.

The honest verdict: what the evidence supports

The physiology is solid. The clinical claims built on top of it are promising but not proven. Here’s how it breaks down.

Claim	Evidence	Verdict
The diaphragm contributes to trunk stability, not just breathing	Repeated lab studies using EMG, pressure and imaging	Well supported
Intra-abdominal pressure helps stiffen the lumbar spine	Lab and mechanical studies	Well supported
High breathing demand reduces the diaphragm’s postural contribution	Lab studies in healthy adults Well supported	Well supported
People with chronic low back pain show different diaphragm behaviour	Small imaging studies (e.g. 18 patients vs 29 controls in Kolář et al., 2012)	Plausible, early
Breathing and continence problems travel with back pain	Large population surveys	Association, not cause
DNS exercise beats other active exercise for back pain	Small, mostly short-term trials	Not established

That last row matters most. The best summary evidence for chronic low back pain says exercise helps, and that no single type is a clear winner (Hayden et al., 2021, Cochrane). DNS is a reasonable, well-reasoned way to deliver exercise. It is not a magic key.

So why use it? Because it gives a clear framework for assessing how someone breathes, stabilises and moves, and for linking those findings to a specific plan. The lens is valuable. Overselling it is not.

Try this: three things to notice

These aren’t a diagnosis. They’re a way to start paying attention to how you breathe and brace. Lie on your back with knees bent, or sit tall.

1. Where does the breath go? Place your hands on the sides of your lower ribs, thumbs towards your back. Breathe in through your nose. Do your ribs widen into your hands, sideways and back? Or do your shoulders and upper chest rise first?
2. Where do your ribs sit? Stand side-on to a mirror. Are your lower ribs flared up and forward, with a deep arch in your low back? Or does your rib cage sit stacked over your pelvis?
3. Can you breathe under load? Hold a light object out in front of you at chest height. Can you keep breathing smoothly while you hold it? Or do you hold your breath or tense your neck to keep it steady?

If you noticed upper-chest breathing, flared ribs, or breath-holding, that’s useful information. It isn’t a problem on its own. Plenty of people move this way without pain. It becomes worth exploring when it shows up alongside pain, recurring injury, or a performance plateau.

When to get it checked

Seek urgent medical care (call 000) if you have:

• Chest pain, pressure or tightness
• Sudden or worsening shortness of breath, or breathlessness at rest
• Coughing up blood
• Back pain with numbness around the groin or inner thighs, or new changes to bladder or bowel control Back pain with progressive leg weakness

See your GP promptly if you have:

• Back pain with fever, unexplained weight loss, or a history of cancer
• Back pain after a significant fall or accident
• A cough or breathlessness that isn’t settling

These symptoms need medical assessment first. Breathing drills are not the answer to them.

Working with Kiome Wellness Group

If none of the above applies and you want to understand how you breathe, stabilise and move, that’s what we assess. Sam Rattu, principal physiotherapist at Kiome Wellness Group in East Melbourne, has completed formal Dynamic Neuromuscular Stabilisation training through the Prague School of Rehabilitation. An assessment looks at your

breathing pattern, trunk control and movement together, using DNS and developmental kinesiology principles. You’ll leave with a clear picture of what we found and a plan built around it.

We see clients in clinic at 62 Wellington Parade, East Melbourne, in the community, and via telehealth. Book an assessment online at kiome.au.

References

1. Frank C, Kobesova A, Kolář P. Dynamic neuromuscular stabilization & sports rehabilitation. Int J Sports Phys Ther. 2013;8(1):62–73.
2. Hayden JA, Ellis J, Ogilvie R, Malmivaara A, van Tulder MW. Exercise therapy for chronic low back pain. Cochrane Database Syst Rev. 2021;9(9):CD009790. doi:10.1002/14651858.CD009790.pub2
3. Hodges PW, Gandevia SC. Activation of the human diaphragm during a repetitive postural task. J Physiol. 2000;522(1):165–175. doi:10.1111/j.1469-7793.2000.t01-1-00165.xm
4. Hodges PW, Gandevia SC. Changes in intra-abdominal pressure during postural and respiratory activation of the human diaphragm. J Appl Physiol. 2000;89(3):967–976. doi:10.1152/jappl.2000.89.3.967
5. Hodges PW, Heijnen I, Gandevia SC. Postural activity of the diaphragm is reduced in humans when respiratory demand increases. J Physiol. 2001;537(Pt 3):999–1008. doi:10.1111/j.1469-7793.2001.00999.x
6. Hodges PW, Eriksson AEM, Shirley D, Gandevia SC. Intra-abdominal pressure increases stiffness of the lumbar spine. J Biomech. 2005;38(9):1873–1880. doi:10.1016/j.jbiomech.2004.08.016
7. Kolář P, Šulc J, Kynčl M, Šanda J, Čakrt O, Andel R, Kumagai K, Kobesová A. Postural function of the diaphragm in persons with and without chronic low back pain. J Orthop Sports Phys Ther. 2012;42(4):352–362. doi:10.2519/jospt.2012.3830
8. Smith MD, Russell A, Hodges PW. Disorders of breathing and continence have a stronger association with back pain than obesity and physical activity. Aust J Physiother. 2006;52(1):11–16. doi:10.1016/S0004-9514(06)70057-5

This article is general information only and is not a substitute for individual assessment or medical advice. If you have symptoms, speak with a registered health professional.