I often find myself needing to educate my clients about breathing. On a good day, it may take around 2-3 minutes of education before the priority shifts toward breathing, on other days, it takes much longer, and occasionally, the client's goal of relaxing certain tight muscles trumps my recommendation of improving fundamental functionalities, such as breathing. So here is why I put so much emphasis on breathing.
We often hear the phrase "everything is connected!", and if I had to choose a muscle to tag that slogan, diaphragm will be it! The diaphragm is the main inspiratory muscle, and it is arguably the first muscle that an infant learns to function for survival. The diaphragm originates from 3 different parts of the thorax - the xiphoid process of the sternum, costal bones (mainly the inner surfaces of the cartilages and adjacent bones of the lower 6 ribs), and the lumbar vertebrae (lumbocostal arches). Collectively, the fibers of the diaphragm converges towards the central tendon (or the fibers fan away from the central tendon, whichever way you want to look at it) and it contracts to increase the thoracic cavity for efficient lung expansion. The diaphragm contains 3 openings for important structures to pass through.
From anterior to posterior, superior to inferior, you have the:
1. Caval foramen (at the level of T8): where the inferior vena cava penetrates within the canal. Amazingly the human body has figured out ANOTHER way to help facilitate venous return as we contract the diaphragm, aka. breath.
2. Esophageal hiatus (at the level of T10): Where the esophagus and the vagus nerve passes through. There are definitely sophisticated mechanisms surrounding deglutition or the act of swallowing, but simply put, the physiological advantage of having the esophagus penetrating through a tight hiatus prevents gastric reflux or retroflow of abdominal contents. Why do you think your parents asked you to eat slowly? Well, that is because it allows you to utilize the diaphragm more frequently so the deglutition mechanism will not be overwhelmed by the forceful binge. As for the vagus nerve, it is one of the most sophisticated cranial nerve that is responsible for a numerous responses in the body such as, breathing, speech, sweating, monitoring and regulating normal heartbeat, and gastrointestinal function.
3. Aortic hiatus (at the level of T12): where the aorta, thoracic duct, and azygus vein and artery courses through. Now it is important to know that this hiatus is not traverse the diaphragm, instead, the lumbocostal tendons of the diaphragm (the left and right crus) creates a tunnel for these structure to course through. It makes sense not to allow compression of these structures as the diaphragm contracts, can you imagine if our body is allowed to consistently compress against the aorta? That would not be a smart design at all.
The diaphragm is also the single partition that divides the abdominal content from the thorax, that being said, it has fascial connections (via diaphragmatic ligaments) to the pericardium (via the phrenopericardial ligament), and the lung (via the inferior pulmonary ligament) superiorly, peritoneum, the intestine, kidney and liver inferiorly. Yes, the diaphragm has physical connections to our vicera. But wait, when the diaphragm contracts, it expands the lungs by vertically increasing the thoracic cavity, that means the abdominal contents will get squished? That's the amazing thing about our body, in 2011 Talasz H. et al. found that before inhalation, electrical activity can be observed in the pelvic floor muscles, that means when we have the intent of performing inhalation (whether voluntarily or involuntarily), a subsequent contraction of the pelvic floor is also happening to lower the pelvic floor contents to prevent abdominal structures being compressed.
Still think that the diaphragm is not that important? Well let’s talk about the lumbocostal attachments of the diaphragm. The left and right crus of the diaphragm are the tendons of the diaphragm that extend distally to attach to the lumbar vertebrae, the right extends to the upper 3 lumbar vertebrae (L1 – L3), and the left extends to the upper 2 (L1 – L2). They both blend into the anterior longitudinal ligament for anterior trunk stability, on top of that, each side of the crus expands laterally to form the medial and lateral arcuate ligaments for the support of another 2 amazing structures of our body – the psoas and the quadratus lumborum respectively. WHAT? Yes, diaphragm activity actually affects the activities of the psoas and QL. So the next time you think twice about teaching your clients (especially those who are office workers) how to properly use his/her diaphragm, remember all the connections it has superiorly, inferiorly, medially, and laterally. If you assess that the client has a dysfunctional breathing pattern, whether it is an under utilization of the diaphragm or over-utilization of the diaphragm, the crocodile breathing (see below) is a good introductory breathing exercise that can get them going.
I will talk about the neurological connections of the diaphragm in my next blog post.