Every day since I began learning muscle anatomy and physiology in massage school in 1997, I have studied at least one of my old muscle flash cards each morning, reviewing the origins, insertions, actions, and other characteristics of a randomly selected muscle.
Today it was the diaphragm, the big dome-shaped muscle across the top of your abdomen that pulls the base of your thorax down to help you fill your lungs when you take a breath. I recalled that the psoas, a muscle that lies deep inside your abdomen, running from the front of your lumbar vertebrae to the front of your hip joint, is connected to the diaphragm. The very topmost fibers of the psoas mingle with the diaphragm in a relationship that anatomists call interdigitation (like fingers interlacing).
You can’t quite see the interdigitation in the image at right. Like most anatomy pictures, it has removed the fuzzy myofascial connective tissue that stitches everything together (and obscures the muscles it wants to show). But you can clearly see how the lower part of the diaphragm (below the yellow dot) lines up with, and is adjacent to, the uppermost fibers of the psoas muscle (green dot).
In my morning reverie, I pictured the overall relationship like a big soup ladle, the dome of the diaphragm the bowl and the psoas the handle. I also pictured how as the diaphragm contracted it could pull on the psoas, perhaps causing it to contract a bit. The action of the psoas is to flex the hip, so I thought about how breath could be connected to locomotion, and vice versa. I set that thought aside and got on with my day.
A couple of hours later I was walking from the bus stop to my office. Just as I took a step with my right leg, I sneezed. As I sneezed, I felt my psoas contract and jerk my leg up a bit more. Much like I had imagined in the morning, the connection between the diaphragm and the psoas had pulled taut. As I coughed, my lungs forcefully emptied, pulling my diaphragm up and tugging on the psoas via the myofascial interdigitation, giving that one step a little more flexion than my non-sneezing steps.
OK, this whole post may just be some weird massage therapist TMI, but I found this interesting and instructive. It reminds me of that drawing in Ida Rolf’s book about how the web of fascia in our bodies ties together remote and apparently disparate parts of our body, connecting large swaths of our body like the fabric in a sweater. Tug at the waist and it can pull on the shoulder, and vice versa. Reminds me, too, that I should spend less time looking at those overly dissected pictures of pure muscle with no connective tissue and more time in a dissection lab.