In the Yogic and Ayurvedic traditions, the physical asanas or postures of yoga have been revered as a fundamental component of the search for optimal health and human longevity. And finally Western science is beginning to confirm and validate why this is the case.
Whilst all of the physical postures of yoga are important, those that involve inversions – where the head is held in a position lower than the pelvis – are particularly revered with regards to the health optimising properties they induce.
Contextualized around the Western framework of how and why inversions provide such powerful health promoting benefits, all of the evidence points to one principal; the galvanizing effect that inversions have our relationship to gravity.
Gravity has a profound effect on the physiology of the human body. As NASA has proven, once humans enter zero gravity, we are subject to severe biomedical problems. Our sense of balance, determined by the vestibular system of the inner ear and calibrated to minute fluid movements, is destroyed. Blood, no longer weighted in the lower torso and legs, floods upwards and the heart speeds up, provoking dehydration and eventually anaemia. Muscles atrophy and bone mass drops precipitously.
Here on earth, gravity slowly but surely weighs us down and saps our strength. We stand, sit, or walk with head almost permanently above the heart, legs and pelvis. As the years rack up, so do the damages. Fat deposits in the face begin to sag and droop, enhancing the visual signs of ageing. Varicose veins and hemorrhoids erupt due to blood pooling in the veins. Weary of incessantly pumping blood through its vast circulatory network, the heart eventually falters. It is no surprise that the ancient yogis called gravity "the silent enemy." Yet yoga provides us with a powerful sleight-of-hand to overcome these problems: Upend oneself and enlist gravity's power to arrest the ravages of that self-same force.
The human body is sensitive to the fluctuations of gravity because it consists of more than 60% water. From the skin in, the body is dense with cells, floating in a bath of intercellular fluid. A complex network of vessels weaves in and around every cell, steadily moving fluids through valves, pumps, and porous membranes, dedicated to transporting, nourishing, washing, and cleansing.
When we invert, tissue fluids in the lower half of the body begin to drain incredibly efficiently and areas of congestion clear. Research shows that if you can remain in an inverted posture for just 3 to 5 minutes, the blood will not only drain quickly to the heart, but tissue fluids will flow more efficiently into the veins and lymph channels of the lower extremities and of the abdominal and pelvic organs, facilitating a healthier exchange of nutrients and wastes between cells and capillaries.
Through doing so, the regular practice of inversions goes on to positively influence three key systems of the body; the cardiovascular, lymphatic and nervous systems.
The Cardiovascular System:
Turning yourself upside down encourages blood flow back to the heart and clears the pooling and congestion of blood in the lower body. According to Pat Layton, physiology teacher for the Lyengar Yoga Institute of San Francisco's Advanced Studies Program, "People have to do aerobics because they don't invert. You have to run really hard—get the heart pumping hard—to circulate blood down to the feet and effectively back to the heart. Not that you shouldn't do aerobics, but inversions are a healthier way to get the benefits to the circulatory system, particularly as you get older."
Furthermore, inversions give the heart a significant rest. The heart works doggedly 24-hours a day to ensure that freshly oxygenated blood makes its way up to the brain and its sensory organs. When inverting, the pressure differential across the body is reversed, and blood floods the carotid arteries in the neck. It is believed that baroreceptors, mechanisms that calibrate blood flow to the brain, sense the increase in blood, and slow the flow, thus reducing blood pressure and heart rate.
The Lymphatic System:
The lymphatic system is responsible for waste removal, fluid balance, and immune system responses. Because the lymphatic system has one-way valves that keep lymph moving towards the heart, when we turn upside down, the entire lymphatic system is stimulated, thus strengthening your immune system. Viparita Karani (legs up the wall) is the best example of this, as it is a mild inversion that one can enjoy for at least five minutes with no stress to the body when we are ill or fatigued. It's interesting to note that for problems like varicose veins and oedema (swelling) of the feet, when lymph is unable to maintain the appropriate fluid balance in the lower extremities, doctors often simply tell people to put their feet up – in other words, invert!
The Nervous System:
When coming down from a head or shoulder stand, it is common to feel clearer and calmer. One reason for this is that being inverted optimises the opening of blood vessels, making them more efficient at dilating and constricting to efficiently shunt blood to the active areas of the brain, increasing nutrient delivery into, and waste removal from, brain cells. This is turn allows the brain, as an organ, to function more effectively, efficiently and optimally.
Inversions may also affect the movements of cerebrospinal fluid (CSF), the juice of the central nervous system which flows from the brain to the spinal cord. When inverted, the top of the skull comes under increased pressure which may promote elasticity in the cranial bones, thus stimulating the production of CSF in the ventricles of the brain.
Whilst more clinical research is needed into the benefits of yogic inversions, what is clear is that these forms of posture provide overwhelming benefits to some of the most important systems within the body. There are also clear reasons to believe that they help to retard the visual and physiological signs of ageing.
Due to the complex nature of many forms of inversions, we recommend starting slowly with easy to perform and hold postures before moving onto the more demanding head and shoulder stands. To facilitate this, find a great teacher who can help select inversions that are safe and suitable for you as an individual, commit to your practice and observe the benefits of regular inversions in yourself over the coming months and years; we can’t recommend it enough!