Yoga for Enhanced Physiologic Health
Craig Metcalf, RN, BSN, E-RYT*
If you practice yoga, you’ve probably experienced firsthand that sense of calm awareness and relaxation that sometimes only a self-care session on your mat can provide. We may not think much about whyyoga makes us feel that way, from a physical perspective, but there are numerous physiologic responses that take place in the human body as a result of engaging the asanas (yoga poses). What follows are two of the body’s major systems and yoga’s positive effects on them. I hope you enjoy these teachings and that they help to further empower you in your practice.
The better our spinal posture, the better our breathing, circulation, and oxygenation throughout the body. Slumping and slouching places undo pressure on the heart muscle which causes it to have to work harder over time to pump blood from the heart out to the rest of the body. That added stress on the heart muscle can eventually lead to improper functioning of the heart chambers and valves. Yoga can help to reduce the added stress to the heart through promoting improved spinal alignment. In addition, yoga poses – coupled with the “ocean breathing” – help to reduce blood pressure and lower heart rate. This occurs because mindful movement and yoga breathing both tap into the parasympathetic side of our autonomic nervous system. This is the side of the nervous system which elicits a relaxation response (rest and digest). When we activate the parasympathetic, smooth muscle which lines our blood vessels begins to relax, allowing the blood vessels to widen, which lowers resistance inside the vessel and, therefore, reduces blood pressure. When this happens, the heart doesn’t have to work as hard to pump blood and oxygen throughout the body, so heart rate is decreased. And, because we’ve increased the oxygen levels within the blood through our yoga breathing, we help to better oxygenate the entire body. As the poses reduce tension within the muscles and various organs, there is a subsequent increase in blood circulation to those muscles and organs. And as the yoga breathing heightens the oxygen levels in the blood that’s flowing in, those muscles and organs are encouraged to become homeostatic, or balanced in their functioning and metabolism. From a physiologic perspective, one of the main reasons why we feel so relaxed and calm after a yoga session is because the body is then better-oxygenated, which means all the body’s systems aren’t fighting so hard to maintain a balanced state. When the body experiences this homeostatic state, we naturally feel more relaxed, calm, and at ease.
Sitting atop our kidneys are the adrenal glands. As part of the endocrine system, the adrenal glands are responsible for producing certain hormones which help to regulate various bodily processes. Two of the major hormones secreted from the adrenals are epinephrine (adrenaline) and cortisol. These are stress hormones, produced and released during times of…you guessed it…stress. We often experience the effects of epinephrine when we’re suddenly frightened or faced with a situation which calls for an immediate response, such as when a bus is careening towards us and we need to move FAST. This corresponds with our “fight or flight” response and is associated with the other side of our autonomic nervous system, the sympathetic. Epinephrine functions with lightning speed, travelling along nerves as opposed to within the bloodstream. It takes this route because we need the effects to kick in right away instead of more slowly over time. Epinephrine also metabolizes quickly, being broken down and excreted from the body in a relatively short time. Cortisol, on the other hand, functions on a slower and longer-term basis. From an evolutionary perspective, cortisol is great because down through history it has helped human beings survive bouts of famine. It does so by slowing down the rate at which body fat is used as a source of energy when no food is available for relatively long periods of time. (Incidentally, this can explain why someone who leads a high-stress lifestyle and is trying to lose weight doesn’t seem to get good results with increased exercise and/or dieting. The high levels of stress-related cortisol are, in part, preventing the breakdown of body fat. Such an individual would experience better results if they also learned techniques for managing stress levels more effectively, helping to reduce cortisol levels. But I digress…) However, in the developed world most of us aren’t faced with famine conditions…but we still produce cortisol, many times to an unhealthy degree. Our cortisol production is related to life-stressors; layoffs, mortgages, student debt, toxic relationships, and the like. Because cortisol travels through the bloodstream as opposed to neural pathways, it takes longer to metabolize and excrete from the body. The higher our stress levels and the more chaotic our life feels, the higher our cortisol levels will be because we’re not provided an opportunity to decompress and allow cortisol to metabolize effectively. In short, we just keep adding on and adding on with each stress-laden day. Now, cortisol is a fat-soluble substance which means it has the ability to penetrate the wall of our body’s cells. Since it does travel through the blood vessels, prolonged exposure to cortisol (as a result of unmanaged stress levels) can eventually lead to blood vessel damage. When cortisol penetrates the cell wall of our arterial lining, for instance, it can leave the lining of the blood vessel with tiny micro-tears. These micro-tears, when viewed under a microscope, appear jagged and frayed, almost like tiny little shark teeth. When a fat globule or a molecule of cholesterol passes by, it can get hooked onto those little teeth, causing it to become stuck inside the artery. As other fat particles float by they are attracted to the original particle and begin to accumulate over time. This accumulation can eventually lead to an arterial plaque and subsequent arterial blockage. Such a blockage can, of course, lead to more serious cardiovascular issues, such as myocardial infarction (heart attack) and cerebrovascular accident (stroke). (Do ya like how I tied this back to the previous section? Testament to the fact that no part of our body is an island unto itself.) When we practice yoga and yoga breathing, we again tap into the parasympathetic which allows those adrenal glands to take a break. Consistently practiced, yoga can help to reduce overall cortisol levels through helping us to more effectively manage life’s stressors. When the parasympathetic is activated while we’re on the mat, it gives our body a chance to more effectively metabolize the cortisol that’s already there and subsequently helps to prevent more cortisol from being released into the bloodstream. Over time, this helps to further protect our overall health and wellness.
These are but two of the body’s systems and how yoga can benefit the state of their functioning. But yoga can actually help promote more efficient and effective functioning of all the body’s systems. I’ll try and touch on the others in future posts. In the meantime, enjoy your practice, self-care every day, and enjoy your journey.
*Craig Metcalf is a Registered Yoga Teacher and Registered Nurse. He received his Yoga Teaching Training (YTT) through Greenville Yoga and has been teaching yoga and meditation for over ten years. In conjunction with his nursing practice, Craig has engaged extensive training in the areas of yoga anatomy and physiology. He enjoys sharing with others what he has learned along the way as a means of helping to empower his students on their yoga and meditation paths.