The Diaphragm PAradox
Updated: Dec 24, 2022
Ever wonder why you drop to the ground after a hard workout?
First and foremost, it lowers the load on your heart improving its ability to circulate blood and oxygen to the body. But there is another reason of which you may not have thought; it has to do with the diaphragm (a profoundly important, dome-shaped muscle in your thorax, separating your chest cavity from your abdominal cavity).
It is widely known that the diaphragm is essential for proper respiration (a la belly breathing, diaphragmatic breathing, yoga, meditation, etc). What is not so widely known is its roll in creating/modulating trunk stiffness, and therefore, contributing to overall trunk stability. To keep it short and sweet, the diaphragm generates trunk stiffness via working with the torso musculature to 1) synchronize the muscles of the torso (specifically the abdominal wall & pelvic floor) into a powerful co-contraction and 2) generate/regulate intra-abdominal pressure (IAP).
This dual function of the diaphragm as both a respirator and stabilizer creates a paradox of sorts. Maximal respiration is in direct conflict with maximal spinal stiffness. The more torso stiffness required for a given task, the more intensely the torso must brace. This brace involves a strong contraction of the diaphragm. The stronger the diaphragm contracts, the more its ability to move air in and out of the lungs is compromised. A maximal brace, with the end goal of generating absolute torso stiffness (aka rigidity), requires full contraction of the diaphragm to generate the necessary IAP. This maximal contraction prevents any and all respiration. Respiration, specifically exhalation, requires the diaphragm to relax (for the central tendon to move upward toward the head). If the diaphragm relaxes, IAP is reduced. If IAP is reduced, then torso stiffness is compromised.
Holding our breath for maximal force production, be it very briefly as would happen at impact as a baseball player hits the ball (microseconds) or for longer periods like you would see when Eddie Hall rips 1,000 lbs. off the floor executing a deadlift (3-5 seconds’ish) is normal and dare I say optimal. In these moments where torso stiffness is the brain’s priority, it is acceptable and even necessary to stop respiration.
On the extreme other side of the diaphragm’s function is respiration (which brings us back to the original question: Ever wonder why you drop to the ground after a hard workout?). At the end of a difficult metabolic or aerobic effort, the body’s need for oxygen is high. Because of the dual function of the diaphragm (that of respiration AND stabilization), in moments where oxygen uptake is of primary importance, the brain must reduce the need to stabilize so that the diaphragm can focus on the task at hand…getting oxygen to the body. This is one of the reasons you put your hands on your knees, drop down in all 4’s or lay completely on your back at the end of a difficult workout — you’re exhausted and need as much oxygen as possible as fast as possible. Each of these positions require less of a stabilization effort from the diaphragm, allowing it to focus on respiration. This is the answer to the question at hand. By dropping down to the ground, you are able to breathe better, which increases the rate of oxygen circulation to the much needed hypoxic tissues of the body.
When it becomes dicey are in moments where both high levels of stiffness and respiration are needed. Challenging situations like this are most prevalent in CrossFit. In traditional strength training, one will have adequate rest between efforts (sets) so the respiratory demand remains relatively low. In Crossfit, it is common to perform big strength training movements, such as back squats or cleans, with an elevated heart rate for a sustained amount of time. This places a challenging demand on the dual function of the diaphragm - asking it to participate in both respiration and stabilization simultaneously. Another good example in strength and conditioning are longer carries. With an adequately heavy load, the intensity of the brace is such that respiration is hindered. If you’ve ever done a carry like this (be it a farmer’s walk or yoke carry), you can remember the super short breaths that you had to use. This is for the simple fact that maintaining the requisite stiffness requires the central tendon of the diaphragm to remain relatively close to the pelvis. If you take a large breath, the central tendon of the diaphragm would move too far away from the pelvis, IAP will be lost, and your torso stiffness will reduce - causing you to either put the weight down or to continue with a compromised position that may result in an injury.
This skill of maintaining what I call braced or loaded respiration needs to be trained, particularly if you or your athlete are exposed to such a situation consistently in sport. Below is a workout example of how I would train this. You could also give this workout a go and see what it feels like to challenge the dual function of the diaphragm.
Train hard. Train Smart.
Richard Ulm, DC
Here’s the workout:
8 Minutes (Cals & Carries)
Calories on the Assault Bike or Rower (12/15 calories)
200’ Single Shoulder Sandbag Carry (60lbs / 80 lbs)
*100’ each side