Can You Actually Strengthen the Diaphragm?

 My recent post about sandbag breathing raised a broader issue I'd like to address: Can the diaphragm actually be strengthened through exercise?

The answer is yes. But that doesn’t mean every exercise advertised as “diaphragm strengthening” works for the stated reasons—or that strengthening is necessarily what's happening when an exercise improves diaphragm function.

Rolf Sovik is hardly alone in promoting the idea, so it was perhaps a bit unfair of me to call out only him in my previous post. The Cleveland Clinic says diaphragmatic breathing can strengthen the diaphragm and suggests increasing the effort by placing a book on the abdomen. Harvard Health makes a similar strengthening claim, particularly for people with COPD, and Physiopedia specifically lists sandbag breathing among techniques for strengthening the diaphragm.

There is even evidence that progressive abdominal loading can work as resistance training. A 2024 study of ventilator-dependent patients with chronic respiratory failure used progressively heavier sandbags on the upper abdomen and found increases in respiratory pressure, diaphragm thickness and diaphragm movement after three months.

That’s important evidence—but, as always, context matters. A diaphragm weakened and deconditioned by prolonged mechanical ventilation is in a very different starting state from that of a healthy yoga practitioner. Showing that an atrophied respiratory muscle responds to progressive overload does not establish that a healthy diaphragm needs the same sort of strengthening, much less that sandbag loading is the best way to accomplish it.

There is also a more fundamental problem with the terminology itself.

“Diaphragmatic breathing” is routinely used as a synonym for belly breathing, as though a bulging abdomen proves that the diaphragm is working and a moving rib cage proves that it isn’t. I’ve been arguing against this false dichotomy for decades. Except in cases of paralysis, all breathing is diaphragmatic breathing.

The action of the diaphragm is capable of producing three-dimensional shape change in both the thoracic and abdominal cavities. The crucial distinction is that the thoracic cavity can change both shape and volume, whereas during breathing, the abdominal cavity changes shape but not volume. What is commonly called abdominal “expansion” is therefore more accurately described as a bulging of the abdominal cavity—in the same way one part of a water balloon bulges when another region is squeezed.

Whether diaphragmatic action manifests primarily as abdominal bulging, rib-cage movement, or some combination depends on what parts of the system are stabilized and what parts are free to move. To deliberately produce a belly breath, therefore, we aren’t simply “using the diaphragm.” We are using other muscles to steer the diaphragm’s action toward abdominal shape change while restricting movement elsewhere.

That makes the common recommendation to place a book on the belly particularly interesting. A book isn’t much of a strength-training device. Unless progressively heavier books are being employed, there’s no meaningful progressive overload. What it does extremely well, however, is make abdominal movement easier to feel, and that points toward something that gets lost when every improvement is attributed to strengthening.

Breath training isn’t a one-way process in which exercise strengthens the muscle, leading to better breathing. Anything that increases proprioceptive and interoceptive awareness of respiratory movement changes how the nervous system recruits and coordinates the diaphragm and its associated musculature. Changes in how a muscle is recruited and used can, over time, produce measurable morphological changes in the muscle itself.

So if someone’s diaphragm movement or thickness changes after weeks of breath training, that doesn’t necessarily mean we’ve discovered a clever way of doing the equivalent of diaphragm bench presses. Awareness changes use, use changes function, and function can eventually change structure.

We also know that the diaphragm can be progressively overloaded much more directly by mechanically increasing airway resistance with inspiratory muscle training (IMT) devices. A 2026 randomized trial of professional dancers, for example, found increased inspiratory strength and diaphragm thickness after progressive IMT.

Even more interestingly, research suggests that the diaphragm doesn’t need a “breathing exercise” to receive a training stimulus. A small but fascinating 2004 Journal of Applied Physiology study found increases in diaphragm thickness and inspiratory strength after subjects trained only with sit-ups and biceps curls—activities that substantially increase transdiaphragmatic pressure.

All of this brings me back to a principle I’ve been teaching for decades: There is no single correct way to breathe. But there are correct ways to perform specific breathing techniques.

That’s not a contradiction. A technique is a deliberately imposed pattern: breathe this way, at this rate, with this part of the body stabilized and another part allowed to move. If you’re practicing a particular pranayama or other breath exercise, there are specific actions that define what you’re practicing, and those actions can be performed more or less skillfully.

But the technique itself is not the goal. The value of learning a new way to breathe is that, by definition, you have to unlearn your old way of breathing in order to master it. A technique interrupts habit. It asks the respiratory system to organize itself differently, bringing movements and sensations into awareness that may have disappeared from your repertoire through years of unconscious repetition.

This is why deliberately steering the breath isn’t inherently problematic. Restricting one direction of movement in order to explore another can be an extremely useful practice. The problem arises when the exercise is mistaken for an anatomical ideal—when “practice a belly breath” becomes “belly breathing is the correct way to breathe,” or when a useful sensory exercise becomes evidence that we’ve isolated and strengthened the diaphragm.

We practice unusual and deliberately constrained breathing patterns not because we should breathe that way all the time, but because learning new patterns gives us alternatives to our old ones.

The goal of breath training isn’t to replace an incorrect breathing habit with another, more correct habit—that’s just trading one way of being stuck for another. The goal is resilience and freedom: a respiratory system with enough options to respond appropriately to whatever life asks of it.

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