Breath training: the diaphragm

It’s impossible to understand breathing without talking about the diaphragm. The diaphragm is a dome-shaped muscle located below the lungs. It is anchored to the ribs, thoracic spine (the spine between the base of the neck and lower back), and sternum (breastbone). The diaphragm performs two key roles: drawing air into the lungs and stabilising the core.

Our lungs are predominantly elastic tissue, allowing them to expand and contract as air moves in and out. The lungs cannot inhale or exhale; breathing relies on the diaphragm and intercostal muscles—small muscles between the ribs. The diaphragm is the key breathing muscle. It is responsible for drawing in most of the air we breathe—approximately 75% in normal conditions, while intercostal muscles are responsible for the other 25%.

When our diaphragm contracts, it moves down towards our abdomen. This movement creates a partial vacuum inside our ribcage. This vacuum, or negative pressure, draws air into our lungs. When our diaphragm relaxes, it moves up, forming a dome that increases pressure in the chest cavity. This compresses the lungs, forcing air out. 

As the diaphragm contracts, it also presses down on the organs in the abdominal cavity, creating positive pressure in that space. The result? Our abdomen expands—hence the name belly breathing. 

Therefore, we must relax our front abdominals (the six-pack) when we breathe. If you hold your belly in to maintain the “flat stomach” look, you limit the range your diaphragm can move. The trade off? Dysfunctional breathing—food for thought when wishing for a six-pack. To be clear, pushing the belly out will not help with inhaling air. That movement indicates functional breathing.

The secondary role of the diaphragm is to stabilise the core. When we inhale, the increased pressure in the abdominal cavity helps stabilise the lumbar spine and pelvis (just ask any weightlifter). Along with other core muscles (pelvic floor, transverse abdominus, and multifidus), the diaphragm creates a “cube” that supports the spine and keeps us stable. When fatigued, the diaphragm prioritizes breathing over core stabilization. Therefore, we need to exercise the diaphragm for functional breathing and to build endurance. The question is: How do we exercise that muscle?

The simplest option is to lie down, place one hand on your belly, and the other on your chest. Inhale lightly through the nose and monitor the chest and belly. Minimise the movement of the chest to encourage activation of the diaphragm. 

Another option is to hold your breath at the end of an exhalation. When you feel the urge to breathe (tension in the chest or a slight muscle spasm in the diaphragm), inhale. Repeat 3-5 times with a few normal breaths between each repetition. Take care not to push yourself too hard. If you are prone to anxiety or panic attacks, only do this with guidance from a coach.

If you are a yogi, you can also try pranayama—yogic breathing. However, advanced techniques should only be performed under the guidance of an experienced yoga teacher.

Like any muscle, the diaphragm strengthens with consistent training—start light, build gradually, and notice the improvement in your breath and stability.