Yoga is perhaps the discipline that has taken the art of breathing to its highest level. Through pranayama (term meaning “control of the vital force”), he notably offers techniques aimed at improving health through breath control. Modern research has confirmed that the regular practice of certain breathing exercises is beneficial, both from a physiological point of view – reducing the risk of cardiovascular accident, for example – and psychologically – increasing well-being and reducing stress. More recent results, obtained by American researcher Selma Yildiz and her colleagues at the University of Oregon, have just found a new virtue in it: yogi breathing would optimize the cleaning of neurons, by increasing the speed of circulation of cerebrospinal fluid. , or CSF, the fluid that bathes the inside of our brain and spinal cord.
This fluid has multiple functions. First, it “supports” the brain and protects the neurons from external shocks. But the LCR is not a lake, it is a river. Or rather, it’s an inland sea, with its ebb and flow: it oscillates between the bottom of the spinal cord and the brain, through which it circulates via a complex system of channels and “caves”, perhaps even passing between the brain cells themselves. On this journey, it carries many nutrients and hormones to the nerve cells: this is its second role. In recent years, a third function has been the subject of particular attention by scientists. The CSF plays a crucial role in the elimination of waste products produced by the activity of neurons, which it collects during its circulation – a bit like a sewage system. It would therefore “detoxify” the brain, before passing the waste into the bloodstream, which would bring them to the kidneys or the liver where they are destroyed.
Two main engines
But what is driving this circulation? First, the heart. CSF is produced in the brain from the filtration of some of the blood passing through it, so that each heartbeat sends a pulse which communicates with this fluid and propels it forward. As a result, CSF oscillations follow the rhythm of these beats. However, breathing has a significant influence on this mechanism. Each breath in fact creates a drop in pressure in the thorax, which “sucks in” not only the outside air, but also the blood coming back from the brain. All the blood circulation then accelerates, as well as the heart beats and, by rebound, the CSF. Exhalation, on the other hand, has little effect, because it does not mobilize any muscular action – except during certain activities.
This “breathing engine” is all the more interesting because, unlike the heart, we are able to control it. Would we then be able to optimize CSF circulation in this way? A study published in 2019 by the team of Gökmen Aktas, of the medical-university center of Göttingen, in Germany, already suggested that it was possible: it showed that inhaling in a large and prolonged way accelerates the CSF more than an inspiration short – the depression in the thorax then being stronger and longer. Selma Yildiz and her collaborators have studied the influence of four yogic breathing techniques. All involved slow, deep breathing—participants had to count 3, 4, or 5 seconds of their choice per inhalation and exhalation—without further instruction in any of the techniques, and using different respiratory muscles in the 3 other techniques: either the diaphragm alone (which corresponds to the famous “belly” breathing), or the muscles that spread the lower ribs (both the diaphragm and part of the intercostal muscles), or the muscles of the top of the rib cage.
In their study, which included 18 volunteers aged 18 to 61, the researchers quantified CSF movements (their direction, amplitude and speed) using ultra-fast magnetic resonance imaging methods. They first established baseline values during the participants’ natural breathing, then compared them to the values noted during the practice of the four yogic breathing techniques. As expected, amplifying the breath accelerated the flow of CSF, increasing the suction applied to it. All the breathing modalities studied had this effect, with an acceleration ranging from 16 to 28% depending on the technique. But, and this is what makes the particular interest of this study, the effect was maximum during exercises favoring the contraction of the diaphragm.
The diaphragm, a particularly powerful pump
Why this feature? This point is not addressed by Selma Yildiz and her colleagues, but it deserves attention. The diaphragm is a cupola-shaped muscle that separates the chest from the abdomen. When it contracts, it descends and compresses the abdominal contents – this is why the belly swells on inspiration during diaphragmatic breathing. The abdominal cavity is then in overpressure, which pushes the blood from the veins towards the heart. There follows a marked acceleration of the blood flow, and therefore of the CSF that this flow feeds. The diaphragm, “main respiratory pump”, is thus qualified as “accessory blood pump”. Contracting it, as during yogic breathing, therefore accelerates the circulation of CSF by two mechanisms: the amplification of inspiration itself (also present during costal inspiration) and the increase in cardiac output (absent or minimal during costal inspiration).
A benefit against Alzheimer’s disease?
What to remember from all that ? That breathing contributes to “washing” the brain by promoting the movements of the CSF, recognized as detoxifying. That breathing hard and slowly accentuates this phenomenon. That breathing “yogically”, with your diaphragm, maximizes it even more. This is all the more interesting since an abnormal accumulation of brain waste, in particular the beta-amyloid protein, is suspected to be the cause of certain neurodegenerative pathologies, such as Alzheimer’s disease. It remains to be determined whether diaphragmatic breathing would help fight these diseases.
Note that breathing is not the only “good practice” likely to give a boost to the CSF. In 2019, Nina Fultz, from Boston University, and her colleagues showed that during certain phases of sleep, the circulation of blood and that of the CSF accelerate concomitantly. Sleeping well is therefore also important for cleaning the brain!
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Yoga: breathing that cleans the brain
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