Where exactly is my diaphragm?
The diaphragm is your main muscle of respiration (breathing), and therefore sits at the base of your lungs & ribcage. It's dome-shaped to match the curvature of the bottom of the lungs. (PS—if you are an anatomy nerd, I highly recommend checking out the KenHub page on the diaphragm for some additional interesting perspectives on how the diaphragm appears from all angles, including on X-rays and CT scans!)
But first, the basics: all muscles have an origin and an insertion. The biceps, for example, originates at your shoulder, and then inserts into your elbow. The diaphragm is unique in that it has multiple origin points, and then attaches onto itself. That's right—it's the only muscle in the body to do so! And, it's why picturing the movement of the diaphragm can be more than a little confusing if you don't have a medical degree. 🙃 So here are the details:
Sternum (breastbone), specifically the xiphoid process—that little pointy bit of bone that sticks off of the end of the sternum
Ribs 7-12—both the bones and cartilage
Bones 1-3 of your lumbar spine (lower back), plus the discs and ligaments of those vertebrae
On itself! On its "central tendon," i.e. the middle of the diaphragm muscle.
Crazy! How does it relate to other muscles of the abdomen and lower back?
This is the really cool part about the diaphragm, and also why it tends to be responsible for a lot of underlying muscle dysfunction and even pain in our bodies. The diaphragm actually has ligaments that DIRECTLY CONNECT it to our quadratus lumborum (QL—the muscles on the sides of your lower back) and psoas (the biggest hip flexor)! So, if the diaphragm isn't moving properly or is holding a lot of extra tension, then that tension can pretty easily flow into our lower back and hip muscles. And the reverse is true—chronic tension, spasm, or pain in the lower back and hip flexors can then create tension and issues in the diaphragm! It's all connected…
And, BONUS—note that the diaphragm has holes in it! Your aorta, vena cava, and esophagus all pass through the diaphragm. The aorta is taking blood away from the heart to the rest of your body, vena cava is returning blood from the lower part of the body to the heart, and the esophagus is the tube that carries food into your stomach. This is where hiatal hernias occur - they are a hernia in the diaphragm that allows part of the stomach to move upwards above the diaphragm. This causes heartburn/acid reflux, and even the backflow of food or liquids up into the mouth.
What happens when the diaphragm moves?
When the diaphragm contracts, it flattens (the central tendon moves towards your feet), and by doing so the ribs expand. This creates negative pressure in your thorax to help your lungs fill with air.
Then, the part I always found confusing at first, is that when you exhale the diaphragm is actually relaxing. This allows the volume of the ribcage to decrease, and your lungs to expel air. Check out my favorite YouTube video of this happening, as it shows the diaphragm and ribcage movement from all angles.
So what should my belly and ribcage be doing as I'm completing diaphragmatic breathing?
This is where there is a lot of misinformation about diaphragmatic breathing. Most people do recognize that the belly needs to expand as you inhale (although for a lot of us, initially we are even doing this part backwards!). However, the key to true diaphragmatic breathing is the ribcage movement.
As the central tendon of the diaphragm moves towards the feet upon inhalation, it flattens the natural dome shape of the diaphragm. This in turn assists with increasing intra-abdominal pressure, and the belly moving outwards. However, the key here is that the ribs also need to expand outwards. And, since we know the diaphragm is a 360-degree muscle with attachments to your ribs on the front, sides, and back of the body: we also need to see movement of the ribs on all sides of the body for a true diaphragmatic breath!
Or to put it more simply: diaphragmatic breathing is not JUST belly breathing. It's also expansion of the ribs to the sides and back of the body. (Of course there are more muscles on & in between the ribs themselves that also help with this movement—it's not just the diaphragm!) Then, as you exhale, the diaphragm lifts up towards your head, and the belly falls towards the spine. And another key here: the ribs need to COMPLETELY relax, or fall inwards towards your trunk as well. If you don't relax the ribs fully and exhale fully, then the next breath will be more shallow. And the cycle of impaired or dysfunctional breathing continues.
What about my pelvic floor?
It helps here to think about the diaphragm & pelvic floor like a piston. The curve of the pelvic floor is opposite of the dome of the diaphragm. So as the diaphragm descends towards your feet on an inhale, the pelvic floor also descends or drops away from the body. Then as you exhale, the diaphragm lifts back up towards the head and resumes its natural dome shape. The pelvic floor then also lifts up towards the head, and loses its inverse dome shape or flattens. Click here for a great gif that shows how the diaphragm, pelvic floor, and belly all need to work together! Normally, this is a pretty passive process. But then of course if the rate and force of breathing increases, the belly and pelvic floor also rise to the occasion to meet that demand. So, if you are exhaling quickly or forcefully, the belly and pelvic floor will also contract to help to decrease intra-abdominal pressure, and force the air out of your mouth. PS—this is the mechanism that gets impaired after having babies that can lead to urine leakage with coughing and sneezing! Coughing, sneezing, laughing, yelling, etc are all very forceful exhalations. So, if your pelvic floor & deep abs aren't on board with contracting during these exhalations, then you are more likely to leak urine! A pro tip to help with this is that every time you feel a cough or sneeze coming on, be sure to do your brace and blink/rocket. Then, try to hold these contractions through the duration of the cough or sneeze. See this gif for a great visualization of this movement that includes your bladder!
This is all so helpful! But, I'm wondering what any of this has to do with my nervous system & stress?
This is a wonderful question with another very long and complicated answer! So, check out the next article called “Diaphragmatic Breathing: Give your nervous system a hug!” for more information.
"Cenveo - Drawing Diaphragm, rib cage and lungs during inhalation - English labels" at AnatomyTOOL.org by Cenveo, license: Creative Commons Attribution
Diaphragm anatomy. https://www.kenhub.com/en/library/anatomy/diaphragm