If you've ever attended a yoga class, you've likely heard the term "belly breathing", and have probably learned how to do it yourself. It's often referred to as the best way to breathe, and is taught as a method to avoid shallow breathing. For those who tend to breathe up high in their chests with a short, shallow breath, belly breathing is a great tool for increasing oxygen intake and allowing the diaphragm to get more involved. However, belly breathing can cause trouble just like shallow chest breathing can.
When you belly breathe, your belly expands because you are sending the air pressure of your breath down towards your feet. Ideally, that means that your diaphragm is engaging, pulling down, and creating a vacuum that pulls air into your lungs. This allows them to expand fully and gives you all the oxygen you need. Healthy movement of the diaphragm also stimulates the vagus nerve, which helps with heart health, anxiety, digestion, and more.
Here's the trap: you can expand your belly without taking a deep breath. Try it. Hold your breath and expand your belly. You can do that muscularly without moving air pressure around. Similarly, you can take a low but very shallow breath and expand your belly at the same time.
I regularly see clients who think they are taking a deep breath, but their rib cage barely moves, indicating that their lungs are not actually filling. Almost all of those clients suffer from anxiety of some kind, even though they likely learned belly breathing to stem anxiety. Their breath is often nearly as shallow as before - it's just shifted pressure from high to low in their abdomen and begun to get the diaphragm more involved. When they learn how to take real deep breath, they often get momentarily lightheaded and a little giddy from the amount of oxygen they suddenly have access to! It also relieves anxiety in a way that yoga-instructed belly breathing rarely does.
Deep breathing involves a lot of rib movement. If you've ever watched the rib cage of a professional singer or athlete, you know what I'm talking about. Air pressure (what a singer needs to be heard across a concert hall) and oxygen saturation (what an athlete needs to move as fast as possible) come from creating space inside the rib cage so the lungs can fill completely. Think of how a balloon being blown up expands in all directions at once. When they have the space to do so, lungs work the same way.
Try this: place your hands on your lower ribs. Take a deep breath and find out if your belly breath involves any rib movement at that level. If your hands don't move, that means your lungs are not expanding in that direction. You can use the same test on different parts of your rib cage to see where your lungs expand or don't - along your sides, your chest all the way up to your collarbones, and your back.
Take some time to learn how to actually breathe deeply, and it will serve you well in countless circumstances. Be patient with the places that don't know how to expand yet. Learning takes time.