Runner phenotypes are important to determine so that training can be tailored to suit the specific needs of each runner.As more and more information pours out on a daily basis about functional training and as I call "the movement to movement" sometimes information easily becomes misinformation or missed information altogether. One of the central themes surrounding functional training, or at least it should be, is the importance of the THORACIC DIAPHRAGM.
And yes, this does answer the question, what is the most important muscle, and it doesn't matter if you are a sprinter, a marathoner, or any other sport. The diaphragm is central, pun intended, to every athletic movement and the quality of that movement. And yes it is the THORACIC DIAPHRAGM, there are actually 4 diaphragms in the human body; the CRANIAL, CERVICAL, THORACIC, and PELVIC. All of these have played an integral role within the body and between one another. At the foundation of the functional training and athletic training rests the thoracic diaphragm.
First, let’s discuss the action of the diaphragm, the human lungs work on a negative pressure system which essentially means that when we inhale we are essentially forcing air in, and when we exhale we allowing it to escape, this is a very simple explanation but this is not meant to be a physiology lesson. So when we inhale the diaphragm contracts and moves inferior causing a vacuum for the lungs and when we exhale the diaphragm relaxes and rises to allow air out. During these same actions an incredible thing happens, as the diaphragm contracts and moves downward it builds pressure between itself and the pelvic diaphragm or pelvic floor, this is known as intrabdominal pressure or IAP, this IAP is THE PRIME STABILIZER OF THE SPINE! No not the lumbar musculature, not the abs, and not the mystical CORE that everyone is training into oblivion. Now in order for the diaphragm and IAP to properly stabilize the spine and in effect the rest of the body, we must first remember how to breathe.
"Remember how to breathe?" This is a common patient response, and then they lose their minds when I tell them they can keep themselves out of back pain by learning how to breathe. Stick with me, if you have ever watched an infant breathing, not in a creepy way, you have probably noticed that their giant Buddha-like belly expands and falls with little to no movement of the ribs or chest. This is the exact opposite of how 90% of the adult population breathes. Instead most adults, due to extended amounts of seated posture and general lack of movement start to breathe using accessory breathing muscles in the neck and shoulders. These accessory muscles are only meant to be used for labored breathing, as in exercising. Switching to these backup muscles as the main breathing apparatus leads to shoulder tension, lumbar spine pain, headaches, and a whole host of other problems.
Now that we have discussed the general issues with the thoracic diaphragm, we will now move to why it is an athlete’s most crucial muscle. For the purpose of this article, I will use a distance runner, but this does not mean that the diaphragm is not equally important for non-endurance athletes. All runners have at some time probably heard that you should try to breathe in a 3:2 ratio (3 steps breathing in, 2 steps breathing out) this is supposedly done to keep the runner from landing on the same foot with a full exhalation. This theory on breathing is absolutely right, but it needs more specification: 3:2 ratio of ABDOMINAL BREATHING.
I'm sure some of you reading this are saying, what about the glutes, they are the cannon or the powerhouse for running! What about the quads, runners are always getting a bad rap for being quad dominant. What about, what about, what about...all of these are true, but without the ability to properly breathe using the full potential of the thoracic diaphragm, you are working at a poor efficiency level and power output is decreased.
As I stated before when the diaphragm works properly a tremendous amount of IAP is built which acts as a balloon, or better yet as a WEIGHT BELT! Yeah, that giant leather belt used by powerlifters, well for some reason we were built with a spinal stabilizer that beats any bull-skin, the belly-binding belt you'll ever find. When a runner breathes properly through the abdomen, they link the upper body to the lower, they stabilize the spine, thereby stabilizing what is above and below, and most importantly the diaphragm is, in essence, the best shock absorber of the body. I'm going to nerd out for a second but bear with me, when a muscle is eccentrically loaded, like those of the diaphragm when we exhale, the muscle fibers are introduced to almost double the vibrational load. The muscle fibers do this with only 50% muscle activation, but what does this mean. It means that by breathing via the diaphragm, we are muscularly more efficient, and the increased vibrational load capacity means that ground reaction forces are dampened through the entire body. For an endurance athlete, this is a HUGE deal, when we start running marathons or ultras, every step starts to take a toll, so why not get the most out of each stride.
Diaphragmatic breathing does not only equate to increased efficiency but also increased power. If you have ever had the pleasure of reading Anatomy Trains, then you know that the body is now seen more like one giant muscle with multiple fascial pockets, rather than individual muscles encased in the fascia. For those of you who don't know, fascia is the connective tissue that is infused through EVERY structure of the body, it is much like the thin sinew you see in a nice marbled steak. The importance of paying attention to the fascia for training and treatment purposes grows as the body of research constantly mounts. Back to the diaphragm, these fascial pockets or slings connect all parts of the body, but some areas have stronger connections, such as the fascia around the low back, abdomen, and glutes. When we have the cortical ability to relax the abdomen while still breathing properly we allow for a tremendous power transfer from arm swing, to CORE (I just threw up a little), to the glutes, and finally to the ground. I'm not going into a huge amount of details on this but think of it like a bull-whip, yeah the Indian Jones weapon of choice.
The supple leather of the whip is very flexible, with just a small flick of your arm, the power is transferred down the entire length until it reaches the end with enough power to cut that rose in half that your beautiful side-kick has been holding in her teeth. This transfer of energy in a runner cannot happen without this same type of supple energy transfer through the thoracic diaphragm. Sure, good and sometimes great runners, who have poor breathing habits can make it to the peak of running, but this is true for all sports. Athletes are tremendous compensators, and they always find a way to excel, but it is up to practitioners like myself and others in like fields to educate, treat and train people to maximize their performance and decrease injuries.
"When a man has lost all happiness, he's not alive, call him a BREATHING corpse"