Saturday, May 4, 2013

Investigating the Benefits & Risks of Headstand: Part 2

Part 2 of a three part series on headstand.

by Kathleen Summers, MD, PhD, RYT500

In part one of this series, we investigated the historical importance of the headstand in yoga and learned that it is not mentioned in the classic triad of traditional yoga texts from centuries past. Although the texts describe various asanas and note when they are useful for the treatment of certain medical conditions, there’s no indication that yogis were doing sirsasana back then – or that it’s helpful for any particular condition.

Yet, if you read the various websites out there, just about everything is considered curable by sirsasana. I’ve searched the medical literature and the oldest reliable yoga works I can find in English, and I can’t figure out where they get some of that stuff.

If I had to guess, I would say that much of it originated with a favorite guru of mine, Swami Sivananda. He was a medical doctor, a prolific writer, and by many accounts, a great yogi and healer. He was ahead of his time – but a little behind ours. He died in the early 1960′s, before I was born, and medical science has advanced quite a bit since then.

So, let’s take a fresh look at some of the claims and see what health effects sirsasana may bring.

1)    Detoxes


Turning upside-down helps to get rid of stagnant venous blood and lymphatic fluid. Since it’s exactly those bodily fluids that carry carbon dioxide and other metabolic products, as well as other toxins washed from the cells through natural cleansing processes, returning those fluids back to the heart for further pumping to the liver and kidneys for excretion is important. Using gravity to facilitate a sluggish process is smart. Although it’s particularly helpful for those with bad veins and for those who stand on their feet a lot throughout the day, we can all benefit. Veins and lymphatic channels don’t have muscles within their tubular walls, so they can’t pump alone. When walking, skeletal muscle contraction squeezes the fluids back towards the heart, but it can be an inefficient process.

Inversions employ gravity to improve efficiency in a complimentary way. The increased venous return increases the stroke volume of the heart and thus its cardiac output, so, in a way, you can say that sirsasana improves heart function. But this is a temporary phenomenon related to the extra volume draining from the lower extremities. At some point the reverse happens, and the heart becomes less efficient since it’s harder to pump against gravity to the lower legs, and less and less venous return eventually occurs. In fact, the cause of death in people who have been suspended upside down is heart failure. In other words, the heart simply can’t keep up with the burden of pumping against gravity to the majority of the body’s tissues. It requires too much extra work. (Of course, the extreme situation won’t occur with sirsasana as you would collapse before that happens.)

2)   Treats respiratory illness 


There could be some truth to the claims that turning upside-down may facilitate healing from a chest cold, bronchitis, bronchiectasis, and emphysema. As in #1, gravity will provide an expectorant effect, using this basic force to facilitate the work of cilia. Cilia are fine hair-like projections in the major air tubes that slowly beat back and forth like windshield wipers, pushing mucus and particulate debris up to the oropharynx to be spit out the mouth or swallowed. It won’t rid the body of a virus causing a respiratory illness, but then neither does any of the cough and cold preparations available over-the-counter at the drugstore – or even prescription antibiotics (which kill bacteria and not viruses). It’s another, possibly valid, way to help relieve symptoms of chest congestion. The caveat here is that inverted postures are uncomfortable when sinus congestion is present, and chest congestion and sinus congestion frequently go hand-in-hand. With the latter, you’re working against gravity as more mucus produced will fall into the sinuses rather than out through the nose or swallowed down the oropharynx. You’re probably better off with simple steam and neti.

    3)   Increases cerebral blood flow


    Possibly you might get increased blood flow to the brain by turning upside-down. While it seems logical, it’s never been documented to occur, and the theory completely ignores what we know about auto-regulation. Blood flow to the brain cells and glandular tissue (like the pituitary and pineal glands so often mentioned) is tightly regulated to a narrow range. And even if blood flow were improved so that each cell or gland received more nourishment, it’s an extra step to suggest that this leads to improved memory or better performing, more balanced glands. For sure, there’s no evidence of either, and it’s quite the stretch to suggest that improving blood flow beyond the usual controlled range improves any physiological function. H. David Coulter essentially agrees with me in his book, Anatomy of Hatha Yoga:


    The brain already, on a normal basis, receives a whopping 20% of blood flow from the heart. In an adult, that’s about one liter every minute. You don’t want much more than that, or a condition known as cerebral hyperemia develops, one in which intracranial pressure is so high within the strict confines of the bony skull that it begins to compress and damage delicate brain tissue. There’s also a big problem if the opposite circumstance occurs – too little blood flow. Ischemia develops and brain cells begin to die. So, the body has developed a sensitive and intricate mechanism that tightly controls the amount of blood flowing into the brain. It’s regulated by pressure and metabolic demands – the need to lower carbon dioxide levels, for instance. Blood vessels in the head are able to change the flow of blood through them by altering their diameters. Vascular smooth muscle in arteriolar walls constricts in response to increased wall tension from elevated pressure (when you stand on your head), preventing any large increases in blood flow.

    4)  Strengthens skeletal muscles


    The more you use a muscle, the more you strengthen it. In sirsanasa:
    • Triceps are active with biceps counteracting
    • Deltoids and trapezius work to lift up
    • Erector spinae remains active for stabilization
    • Rectus abdominus works in opposite direction for balance
    • Quadratus lumborum and psoas support lower back and balance pelvis
    • Psoas and gluteus maximus stabilize core to prevent wavering
    • Adductor muscles of thighs bring legs together
    • Quadriceps straighten the knees

    5)  Improves balance


    Yes, this makes a lot of sense. The brain is plastic. It's trainable. You can think of the cerebellum, the part of the brain primarily responsible for balance, as the muscle of balance. The more you work to build the muscle with more challenging tasks, the more balance will improve. There's some evidence to support this theory here and here (although it's not specific to sirsasana).

    6)  Increase flow of subtle energy, or sublimation


    This one is outside the realm of modern medicine, so all we have is theory and you can choose to believe it or not. While some Yoga experts relate chakras to anatomical correlates and describe prana in terms of physiologic energy like nerve conduction, I believe the essences of what's described as esoteric energy is beyond what modern physics is able to measure.

    None of these potential benefits of inversion are confined to sirsasana. The classic early mudra of viparita karani, performed without hands supporting the hips but instead with palms flat on the ground, would also do all of the above.

    References:

    Haennel RG, Teo KK, Snydmiller GD, Quinney HA, Kappagoda CT. Short-term cardiovascular adaptations to vertical head-down suspension. Arch Phys Med Rehabil. 1988 May;69(5):352-7.

    Ray Long. The Key Poses of Yoga: Scientific Keys, Volume II. Bandha Yoga, 2009.

    ****

    Kathleen Summers, MD, PhD, is a contributor to Prevent Yoga Injury. She is a board-certified internist specializing in natural, Yoga-based care. Dr. Summers is a graduate of Northwestern University Medical School in Chicago and holds a second doctorate in neuro-pharmacology from Southern Illinois University. Currently, she is an Adjunct Clinical Instructor at Southern Illinois University School of Medicine, and she is a member of the American College of Physicians, the American Society of Nutrition, and the International Association of Yoga Therapists. 

    During her frequent travels to India, Dr. Summers researches Yoga and its therapies. She enjoys uniting her two passions, Yoga and medicine, and is continually exploring Yoga's healing concepts and integrating them with modern, evidence-based care. Her primary Yoga influences have been the tantric styles of Sivananda and Agama. She holds a 500-hr Yoga teacher training certification. You can follow Dr. Summers on Facebook and Twitter. This article originally appeared on Dr. Summers' blog and is re-posted here with her permission.

    3 comments:

    1. Nice piece of information, I would like to know some more information regarding other yoga practices.

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    2. Yoga is one of the trending exercise which is practiced by people who wants to change their lifestyle into a healthier one. I am one of those practitioners but there is one question that I would like to ask is, is it alright to do yoga while I am taking some supplements such as zinc or even an l arginine benefits What I mean is, does it affect any performance or will it damage my health furthermore?

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    3. This comment has been removed by the author.

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