Breathing is one of your body's most vital functions. Prompted by your brain, your lungs draw in air consciously and unconsciously around the clock, providing oxygen to your blood and vital organs. You may be surprised to learn that your lungs have no muscles of their own. Instead, they rely on a number of other nearby muscles to get their job done.
Diaphragm
When you are sitting or resting, your diaphragm does most of the breathing work. Merck describes your diaphragm as a large sheetlike muscle that forms a dome shape between your lung cavity and your abdominal cavity. It is attached to your sternum, spine and the lower part of your rib cage. When the muscle contracts, it lowers, lengthening and widening the chest cavity. Air rushes into your lungs to fill up the empty space. This is called inhalation or inspiration. When your diaphragm expands, it presses up against your lungs, forcing air out. This is called exhalation or expiration. When you are inactive, breathing is a passive process.
Abdominal/Core Muscles
When you do strenuous exercise, you need to breathe quickly to supply your body with enough oxygen to keep moving. Your diaphragm isn't fast enough or strong enough to keep up with your breathing requirements. This is when your abdominal muscles come into play. The Fit Step website explains that your abdominal muscles are comprised of six muscles located on the front and sides of your torso's lower half. They force active, rather than passive, breathing by expanding and contracting rapidly, causing the diaphragm to move up and down.
Rib Muscles
Your rib muscles--also called intercostal muscles--are situated between your ribs. According to York University's Voice and Speech Source, there are two types of intercostal muscles: internal intercostals, which wrap around the inside of your rib cage, and external intercostals, which wrap around the outside of your rib cage. These muscles give your chest elasticity. As you breathe in and out, they contract and expand, allowing your chest to accommodate your lungs as they inflate and deflate.
Neck/Collarbone Muscles
Your neck and collarbone muscles don't play a large part in your regular breathing. However, they can act as stand-ins when called upon. If your diaphragm and stomach muscles can't function at full capacity because of an illness or injury, they can provide support for your lungs and help keep you breathing.
