Function of the Diaphragm (Health Benefits)
The diaphragm, in normal health, does over 75% of the work of breathing at rest (Ganong, 1995; Castro, 2000). Most modern people, as it is easy to observe, have predominantly chest breathing. Does chest breathing interfere with the health of humans and the normal functioning of the diaphragm? What are the benefits of diaphragmatic breathing?
Two Main Functions of the Diaphragm and Benefits of diaphragmatic breathing
- To regulate efficient O2 delivery and (partial) CO2 elimination. (Note that, while the majority of modern people believe in the deep breathing myth and the poisonous nature of CO2, medical science has found dozens of benefits of CO2 in the human body.)
Respiratory Physiology, by John West, documents that the upper 7% of the lung delivers 4 ml of oxygen per minute, while the lower 13% of the lung brings in 60 ml of oxygen every minute (West, 2000). Therefore, lower parts of the lungs are about 7 times more productive in oxygen transport. While normal breathing at rest has a small tidal volume (only about 500 ml for a 70-kg person), it provides hemoglobin in the arterial blood with up to 98-99% O2 saturation due to the leading role of the diaphragm in the respiratory process.
In contrast, chest breathing is usually larger and deeper (up to 12-18 L/min for minute ventilation, 700-900 mL for tidal volume, and 18-25 breaths/minute in mild forms of heart disease, diabetes, asthma and so forth). But during thoracic breathing, blood oxygen levels are actually reduced due to inhomogeneous gas exchange: lower the parts of the lungs do not get fresh air supply during chest breathing. In certain cases, this pathology (chest breathing) can greatly contribute to or even lead to pneumoperitoneum, emphysema, chronic respiratory fatigue, severe asthma, bronchitis, cystic fibrosis, heart disease, diabetes, cancer tumor growth, and other pathologies.
- To perform lymphatic drainage of the lymph nodes from the visceral organs. The diaphragm is a lymphatic pump, since about 60% of all lymph nodes in the human body are located just under the diaphragm. Dr. Shields, in his study, "Lymph, lymph glands, and homeostasis" (Shields, 1992), reported that diaphragmatic breathing stimulates the cleansing of the lymph nodes by creating a negative pressure pulling the lymph through the lymphatic system. This increases the rate of toxic elimination by about 15 times.
Chest breathing at rest causes lymphatic stagnation in the stomach, pancreas, spleen, liver, kidneys, large and small colon, and other organs. Hence, effective lymphatic drainage is also among the benefits of diaphragmatic breathing. This may sound as confusing as trying to explain how does an annuity work to someone who has never heard of one, but simply each function works off each other to create the bigger picture.
Other functions and benefits of using the diaphragm (not related to breathing)
- To help in defecation, urination, and vomiting by increasing the intra-abdominal pressure. All these processes are mainly reflexive in their nature and the contribution of the diaphragm to these processes, in health, is small but valuable.
However, alveolar hyperventilation (or elevated minute ventilation rates, due to thoracic breathing) can lead to spasm in the muscles of the lower digestive tract, causing constipation. People with constipation strain themselves too much (in the elderly, this often results in the formation of diverticula). But with regular, gentle diaphragmatic breathing, bowel movements occur more easily - and it becomes unnecessary to use the diaphragm forcefully (which creates high intra-abdominal pressure) to make the bowel movement.
- To help in the production of speech (with one's voice) and other sounds (e.g., laughter) by changing the intra-abdominal pressure. In normal health, high CO2 levels dilate the airways, making air movements easier, while the diaphragm naturally remains relaxed. In this case, the diaphragm plays a main role in the generation of speech sounds and voice sounds.
When we switch to thoracic breathing (as during unnoticeable hyperventilation), this function of the diaphragm is taken over by the chest muscles. The resulting hypocapnia constricts bronchi and bronchioles, leading to a tenser voice and a higher pitch of the voice. This effect is especially noticeable during singing, so it is not a surprise that singing teachers encourage diaphragmatic breathing in their students.
Causes of the diaphragm dysfunction and chest breathing in modern people
Hyperventilation is the main, and generally the only, cause of chest breathing in modern people and their inability to enjoy the diaphragmatic breathing benefits. Why? Because alveolar hypocapnia, regardless of the presence of the ventilation-perfusion mismatch, leads to hypoxia in body cells, including the muscle cells of the diaphragm. As a result, the diaphragm gets into a state of spasm. If breathing gets slower or closer to the norm (e.g., due to breathing retraining), the oxygen level in the diaphragm will increase and it will be again the main respiratory muscle used for breathing at rest.
How to restore function to the diaphragm
Diaphragm function can be improved using simple Diaphragmatic Breathing Exercises, Techniques and Instructions. In order to achieve constant abdominal breathing, it is necessary to use more special techniques. Medical research and numerous clinical trials suggest that resistive breathing (e.g., pursed lip breathing and western respiratory sport trainers) improves diaphragm function and lung function results. However, there are faster and better ways to restore the functioning of the diaphragm and enjoy the benefits of diaphragmatic breathing. You can find the names of these techniques right below here as your bonus content.
Here are 2 great abstracts from medical studies that provide clear and accurate information about function of diaphragm in health and disease.
Castro M. Control of breathing. In: Physiology, Berne RM, Levy MN (eds), 4-th edition, Mosby, St. Louis, 1998.
Ganong WF, Review of medical physiology, 15-th ed., 1995, Prentice Hall Int., London.
Shields JW, MD, Lymph, lymph glands, and homeostasis, Lymphology, Dec. 1992, 25, 4: 147.
West JB. Respiratory physiology: the essentials. 6th ed. Philadelphia: Lippincott, Williams and Wilkins; 2000.
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