Updated: Jun 15
Yoga teachers often identify belly breathing as the best type of breath. Belly breathing occurs when the abdomen is displaced outward as a result of the diaphragm pressing down onto the abdominal contents. (Just to be clear: Even though asking someone to breathe down into the belly can be a useful and valid cue, no air is of course descending into the belly, only into the lungs.) Some incorrectly think that belly breathing is synonymous with diaphragmatic breathing, but, in fact, one can breathe diaphragmatically with only the chest moving while the belly remains still.
Rib cages can vary between the sexes and between ages. Women’s ribs tend to point down significantly more than men’s (Bellemare et al., 2003). As a result, women’s ribs are more likely to move during respiration than men’s and women’s rib cages can achieve a greater volume expansion. Evolutionarily, this may suit the lack of abdominal displacement possible during pregnancy.
The ribs of the elderly and newborns also point outward more than downward, so their ribs cannot expand outward during inhalation, and they both will be inclined to belly breathe (Weaver et al., 2014). Think of a baby lying on their back and how much the belly distends outward on inhalation. This is not because they are breathing correctly and adults are breathing poorly; rather, our bodies naturally change through the course of our lives. Therefore, seeing someone’s chest rise as they breathe does not necessarily mean that they are breathing incorrectly or that they have dysfunctional breathing.
The "three-part breath," a practice common in yoga, is where you try to first breathe down into the belly, then the middle of the chest, then up into the collar bones. It is sometimes likened to filling a glass with water. However, when it comes to our lungs, air does not follow the principles of fluid dynamics. It follows the principles of aerodynamics. Imagine blowing up a balloon and trying to fill it from the base of the balloon and moving upward. Of course, that is impossible.
In a person with a complete upper spinal cord injury, the abdominal muscles are completely paralyzed (Estenne et al., 2000). As a result, the belly distends with each inhale, which makes the rib cage contract, which is described as “paradoxical breathing.” A person with complete upper spinal cord injury will therefore experience inefficient breathing, and it can be difficult for them to increase breathing rate or deepen their breath, as is required when performing exercise.
Furthermore, engagement of the abs also affects belly breathing. Belly breathing requires the contents of the abdomen to be displaced outwardly. If the abdominal muscles are strongly contracting, say during core work or a physically demanding yoga pose, the abdominal contents cannot displace outwardly. The abdominal muscles are busy making a stiff wall on all sides of the abdomen. Therefore, the ribs are more likely to move during these more strenuous tasks.
So, belly breathing might be a great practice for slowing the breath and bringing our mind’s focus to the breath. However, rib cage angles vary between sexes and between ages. Some populations, namely women, are more likely to experience rib cage movement even during diaphragmatic breathing while other populations, namely newborns and the elderly, are more likely to see their bellies move as they breathe. We cannot choose which parts of our lungs the air fills and our bellies are unlikely to move if we are stiffening our abdominal wall through contraction of the abs. Rather than thinking that the best and only way to breathe is in the belly, we should remember that the breathing type will vary depending on the task at hand.
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This post is adapted from my book The Physiology of Yoga.
Bellemare, F., Jeanneret, A., & Couture, J. (2003). Sex differences in thoracic dimensions and configuration. American journal of respiratory and critical care medicine, 168(3), 305-312.
Estenne, M., Pinet, C., & De Troyer, A. (2000). Abdominal muscle strength in patients with tetraplegia. American journal of respiratory and critical care medicine, 161(3), 707-712.
Weaver, A. A., Schoell, S. L., & Stitzel, J. D. (2014). Morphometric analysis of variation in the ribs with age and sex. Journal of Anatomy, 225(2), 246-261.