The Diaphragm – Anatomy Highlight

diaphragm anatomy

The diaphragm is an under-appreciated muscle that influences many aspects of our physical and mental health. While the diaphragm’s main role is in respiration (breathing), it also plays a part in a wide range of body processes including nerve function, lower back health, stress vs. relaxation, digestion, and more. In this article, I’ll go over the basic anatomy of the diaphragm, briefly touch on its main role in breathing, and then delve into the other processes that it impacts.

Where is the Diaphragm?

Your diaphragm serves as a physical partition between the thoracic cavity (the area inside your rib cage where your heart and lungs are found) and the abdominal cavity (which contains your stomach, intestines, and other major bodily organs). It originates from the xiphoid process, the 6 lower ribs, and the first 2-3 lumbar vertebrae. In its center, the diaphragm is composed of a fibrous tendon structure called an aponeurosis that has no bony attachment.

Where is the diaphragm?

There are a few important anatomical interactions involving the diaphragm I would like to touch on. Because the diaphragm covers the space between the thoracic cavity and the abdominal cavity, it has three major openings that allow important structures to pass through. Important arteries (carrying oxygenated blood from your heart to the body), veins (carrying deoxygenated blood back to the heart), lymph vessels (the pathways of your immune system), nerves, and the esophagus (transporting ingested food to the stomach) all pass through these openings. Crucial among these are the trunks of the vagus nerve. The vagus nerve is an immensely important structure that regulates the function of many internal organs, the parasympathetic nervous system, and even serves as a primary connection between the gut and brain. The diaphragm also shares fascial connections to both the psoas major (read my article on the psoas) and quadratus lumborum muscles.

Diaphragm anatomy

What Does The Diaphragm Do?

As mentioned above, the main function of the diaphragm is in breathing. As the diaphragm contracts, it pulls down. This movement increases pressure in the abdominal cavity while decreasing pressure in the thoracic cavity. As the pressure in the thoracic cavity drops, the lungs expand drawing in outside air. To learn more about this process, check out my previous article that goes over the process of breathing. More diaphragm excursion during breathing translates into more air drawn into the lungs and greater effective oxygen intake.

Diaphragm in breathing

The Diaphragm and The Autonomic Nervous System

It has been demonstrated through numerous studies that deep breathing using the diaphragm increases parasympathetic nervous system activation, reduces stress, and produces numerous positive physiologic effects. Breathing in this way can slow heart rate, reduce blood pressure, promote healthy digestion, improve heart rate variability, and even decrease symptoms of anxiety and depression. The diaphragm influences the autonomic nervous system through multiple pathways.

Deep, diaphragmatic breathing stimulates the vagus nerve directly as the signals that control the rate of breathing pass along the vagus nerve. Thus, when we voluntarily slow the rate of breathing, the vagus nerve is directly stimulated (Source).

The diaphragm can also influence the autonomic nervous system more indirectly. This indirect route essentially states that breathing in a slow, controlled manner voluntarily replicates the natural state of the body when relaxed. By adopting this relaxed physiologic state you signal to your central nervous system that you are safe and calm, leading to greater parasympathetic activation (Source).

Finally, because the trunks of the vagus nerve pass directly through an opening in the diaphragm some have theorized that movement of the diaphragm can mechanically stimulate the vagus nerve directly.

The Diaphragm, Ribs, and Spine

Research has found that individuals with chronic lower back pain often show altered breathing patterns involving less movement of the diaphragm and poor diaphragm activity during loading (Source). This fits well with the mechanism by which the diaphragm contributes to postural stability. The diaphragm works together with the pelvic floor, multifidus, and transversus abdominus to increase intra-abdominal pressure, creating stability for your spine. It also makes logical sense that because the diaphragm is physically attached to the lower ribcage and spine, it can directly influence movement and dysfunction of these areas.


The Diaphragm, Psoas Major, and Quadratus Lumborum

As mentioned above, the diaphragm has direct mechanical fascial connections to the psoas major and quadratus lumborum (QL) muscles. Both the psoas and the QL play play a role in stability and movement of the trunk and pelvis. They are both incredibly important in general function as well as athletic performance. Because of their close relationship with the diaphragm, dysfunction in either muscle can create dysfunction in the diaphragm. The reverse is also true in that diaphragmatic dysfunction can create dysfunction of the psoas or QL.

The Diaphragm and Digestion

The diaphragm plays a role in digestive function both directly and indirectly. Directly, contraction of the diaphragm creates compression and movement in the abdominal cavity. This movement mechanically assists with digestion as it “massages” the stomach and intestines. Indirectly, the diaphragm’s promotion of parasympathetic nervous system activation also stimulates an increase in digestive activity.

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How to Train Your Diaphragm

Now that you understand why a strong, healthy diaphragm is important let’s go over how to train it. Training the diaphragm is relatively simple, but there are many available techniques. I’ll go over two in this article that you can easily start with.

Technique 1: The Sniff

This is a good way to get a feel for the kind of movement you can expect while using your diaphragm for breathing.

  1. Start laying on your back with both knees bent and feet flat on the floor
  2. Place one hand on your belly and one on your chest
  3. Inhale quickly through your nose as if sniffing forcefully
  4. You should feel a rapid rise in your belly with little to no movement in your chest

That rise of your belly is created by the contraction of your diaphragm. As the diaphragm contracts and pushes down into your abdomen, it pushes your belly outward.

Practice this technique just to get a feel for diaphragm activation and contraction, then move on to technique 2, below.

Technique 2: Long Exhale Diaphragmatic Breathing

Exhale emphasized breathing produces immediate increases in parasympathetic nervous system activation. This creates a feeling of calm and a powerful reduction in stress. In this version of the technique, you will also focus on a deep diaphragmatic breath in order to build diaphragm strength and control.

  1. Start laying on your back with both knees bent and feet flat on the floor
  2. Place one hand on your belly and one on your chest
  3. Inhale through your nose deeply, expanding first into your belly starting from the bottom and gradually filling up until your entire belly is full of air
  4. Allow the expansion to then spread into your chest until you feel you cannot pull in any more air
  5. Exhale as slowly as you can either through your nose or mouth (practice both ways)

Start with practicing this technique for five minutes. When you feel comfortable with it, increase that to ten minutes. I recommend starting your practice laying on your back, but you should eventually be able to perform these deep breaths in any position.

Closing Comments

Proper function of the diaphragm promotes parasympathetic activation, reduces stress, assists with digestion, improves postural stability, maintains spine health/function, and increases oxygen uptake. The two techniques above will give you a great start in training your diaphragm. Get to it, and reach out if you have any questions!

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Health Advice Disclaimer

This article provides examples that are applicable to many, but not all people.  They are based on typical presentations seen in my personal clinical practice.  This information represents common findings in the population discussed, but can in no way take the place of professional evaluation and treatment by a licensed medical practitioner.  It is impossible to provide 100% accurate diagnosis or prognosis without a thorough physical examination and likewise the advice given for management or prevention of any injury cannot be deemed fully accurate in the absence of this examination. 

If you are currently experiencing any pain or injury, seek professional evaluation before undertaking this or any exercise program.  Ensure that you are medically cleared for exercise before undertaking any exercise program.  Significant injury risk may occur if you do not seek proper evaluation.  No guarantees of specific outcome are expressly made or implied in this article. 

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