Inversions help with blood pressure issues. This has been born out in numerous studies.
Some inversions, such as headstands and shoulder stands, however, can offer significant risks of physical injury. It turns out the small bones in the neck just beneath the skull, C1 through C7, are crafted to hold a 10-15 pound mass known as the human head. They were not designed, on the other hand, to hold the entire weight of a human body. Turns out, they suffer greatly from headstands and shoulder stands, especially when practiced by the ill-informed.
There are ways to approach these extreme inversions that are safer, at least in theory. But is the benefit worth the risk? Ask the healthy 28-year-old lady who suffered a stroke while in a classic wheel pose. Her head was wretched back too far while the crown was in contact with her yoga mat.
She had difficulty getting up, and when helped into a standing position, was unable to walk without assistance. The woman was rushed to the hospital. She had no sensation on the right side of her body; her left arm and leg responded poorly to her commands. Her eyes kept glancing involuntarily to the left. And the left side of her face showed a contracted pupil, a drooping upper eyelid and a rising lower lid — a cluster of symptoms known as Horner’s syndrome. Nagler reported that the woman also had a tendency to fall to the left.
- Broad, William J., The Science of Yoga, New York, NY, Simon and Schuster Paperbacks, 2012
Is it worth the risk? There are several anecdotal accounts of stroke caused by inversions in yoga. Is it worth the risk? Turns out, that's a personal question. Up to you. You gotta make the call for yourself. For me and my house, I'll take a more gentle inversion over the risk of injury.
Science is good. Yoga is good. Why not practice the one with an eye towards the other? Just a thought.