In this article I will explain what the diaphragm muscle is, why it is essential and how it works. I will also outline the characteristics of belly breathing and diaphragmatic rib cage breathing and the differences between them.
What is the diaphragm?
The diaphragm is a dome-shaped muscle which has the form of a sheet. It is situated in between your rib cage and abdomen. Imagine your torso is split in two halves. The upper part (thoracic cavity) contains your lungs, heart, trachea, esophagus and thymus. The lower part (abdominal cavity) contains your stomach, liver, gallbladder, small intestine, large intestine, kidneys, spleen, bladder, pancreas, etc. The diaphragm is the muscle dividing the thoracic from the abdominal cavity. It is attached to your sternum, at the sides of your lower ribs and to your spine. If you touch the middle of your sternum with your finger, you will feel where the top of the dome is. The diaphragm contracts rhythmically and most of the time involuntarily while you are breathing.
How does it work?
The diaphragm is the major muscle in respiration. When you breathe in your brain tells your diaphragm to contract, move down towards the bottom of your rib cage. This moves all the abdomen organs including your stomach down, so your belly expands. The lungs expand down and to the sides because of the extra space provided by the diaphragm. When inhalation is complete your brain signals your diaphragm to back to its original position, the muscle relaxes and your belly collapses. There is now more space for your abdomen organs and less space for your lungs. They deflate like a balloon.
Why is it important?
The diaphragm plays an essential role in Pranayama (breathing exercises) and Asana practice. There are two types of breathing which are not directly initiated by your lungs: belly breathing and diaphragmatic rib cage breathing. Although these two are often referred to as the same, they have some differences, which we will outline now. Belly breathing if done wrong, can even have negative effects. Diaphragmatic or rib cage breathing is the foundation of Pranayama and meditation.
This type of breathing is great to practice when you want to fall asleep faster or just relax. It helps with stress and anxiety by stimulating the vagus nerve and activating the parasympathetic nervous system PNS (rest and digest conditions).
Belly (abdominal) breathing
In belly breathing, which is also referred to as abdominal breathing the belly rises and falls while the chest remains relaxed. On the inhalation the diaphragm moves down pushing the abdomen organs down. On the inhalation the diaphragm goes back up, relaxes and the abdomen moves up.
Belly breathing is much more efficient method than chest breathing because of the lungs form. They are narrower at the top and wider at the bottom, where most of the blood is situated. Belly breathing uses the lower wider part of the lungs in contrast to chest breathing which uses the upper part of the lungs. Despite this, there are some limitations of belly breathing.
Pros and cons
It is great to practice if you have insomnia and want to fall asleep. However, if you want to mediate or practice Pranayama you need mental concentration and belly breathing is not suitable for that. In addition, it does not engage your core muscles and doesn’t make them more stable. This is only the case for diaphragmatic breathing.
Diaphragmatic rib cage breathing
In diaphragmatic breathing, also known as rib cage breathing, the lower ribs and the middle back expand and collapse. In contrast to belly breathing where only the abdomen moves, diaphragmatic breathing is a 3 dimensional movement involving the low ribs and middle back. The belly remains almost still. The right and left lung are not of the same size. The right lung consists of upper, middle and lower lobes, while the left one only has upper and lower lobes and is usually smaller because it has to make space for the heart.
In diaphragmatic breathing the lower lobes of the lungs are utilised. This is where also most of the blood is located. The lower lobes expand in all directions, also towards the back. By creating a multi-dimensional expansion the abdomen is also being engaged.
On the inhalation you can slightly contract he abdominal muscles to prevent the belly from rising. This pushes the abdominal organs up towards the base of the diaphragm, so the top of the dome cannot move down (like in belly breathing). The dome is now supported from below with the abdomen organs. The rib cage expands in all directions: to the front, to the back and to the sides, because the diaphragm is attached to it. Thoracic cavity is now much wider and bigger. On the exhalation the diaphragm relaxes, the lungs move down and the top of the dome goes up to its original position
Pros and cons
Diaphragmatic rib cage breathing is especially good for improving your backbends because it expands the rib cage, in particular you can use the exhalation phase to deepen your backbend. Some good backbends to start with are Ustrasana (Camel Pose), Urdhva Dhanurasana (Wheel Pose) or Dhanurasana (Bow Pose). However, to learn diaphragmatic breathing it is best to start practicing it while lying down before using it in your backbends.
Belly breathing vs. diaphragmatic breathing
Although some websites like Harvard.edu, Healthline and even Wikipedia say belly breathing and diaphragmatic rib cage breathing are the same, they are not. In belly breathing the belly expands and collapses, whereas the main movement in diaphragmatic breathing comes from the lower ribs. Belly breathing is more suitable for beginners or people used to chest breathing, as it’s easier to learn. It is a great way to move away from chest/Clavicular breathing and instead use the belly. Diaphragmatic rib cage breathing requires more advance practice to master. If done properly, it can be much more beneficial because it uses the lower lobes of the lungs. Also, it is very relaxing and much better for core muscles stabilisation than belly breathing.
A great post about the differences between them is the one I found from Marco Pino at path2yoga and one which inspired me to write this article, so for more information please check out his post. You can find another great explanation in this post Yogajournal.