I received quite a few comments, on my personal Facebook page, to my article on headstand. Below are my clarifying responses. While I don’t include the original comments from my FB friends, they are fairly obvious within the context of my replies.
Reply to W.
Fan or not, Hector’s study is hugely important to biomechanics literature as it relates to yoga and to yoga literature as it relates to mechanical considerations of asana. There is very little out there that looks at the mechanics of yoga postures and their mechanical consequences. Hector was not trying to prove that loading the neck was bad. She set out to determine how much load is happening, rate of loading, center of pressure, and neck angle; contextualize these findings within what we already know about spine mechanics (lots); and apply this to an increasingly popular and controversial yoga posture. It’s through this extrapolation that one might conclude (me in this case) that unnaturally loading the neck is not good and that sirsasana provides the type of loading known to cause chronic and acute injuries.
You make a great point about loading of the neck not being limited to compressive forces. There are indeed tensile forces loading our cervical spine via our musculature. Buried within the 100+ pages of Hector’s thesis, she references studies that look at the minimal forces shown to cause cervical failure. These force studies, in humans, must be done in cadavers for obvious reasons. So, to account for the activity of surrounding musculature that would be found in a living person, cadavers’ skeletons were anatomically restrained in order to simulate the stabilizing properties of neck musculature. What they found, surprisingly I assume, is that larger fractures and forces were generated. This indicates that muscular stability or restraint may not increase tolerance for higher loads. Other researchers found that age, gender, disease, endocrine function, congenital factors and arthritis all affect tolerance values for cervical failure. Coincidentally, she does discuss African wood bearers, who are practiced at carrying large loads on their heads. In one small study, 90% of male wood bearers exhibited cervical degeneration compared to 23% of the control group. Elimination of natural cervical lordosis was seen, which puts the spine into pre-flexion – a known condition for cervical failure under axial loading. In other studies, females carrying large loads of wood had more prolapsed discs, herniations, and listhesis than those with moderate loads.
Ethically, a clinical study that seeks to prove that neck injuries are caused by certain loads can’t and won’t be performed on living humans, so we have to rely on research studies with cadavers or retrospective studies like those with wood bearers – which may be the closest thing we have to proving cervical loads do indeed cause injuries. When I put all of this together – case studies, biomechanical studies, anthropological studies with wood carriers, clinical studies done on glaucoma & blood pressure, and all the anecdotal studies from yoga teachers and practitioners, the evidence is clear, if not overwhelming, that supporting more than 8% of your body weight on your neck is dumb. Even if you do strengthen your cervical bones and other tissues by loading, I can’t imagine you strengthen it over five fold. But, again, the studies have not been done, which is why Hector’s study is so important.
Reply to M.
Iyengar taught, in his books anyway, that the full weight of your body should be on your head in sirsasana. Fortunately, many good teachers, like you, instruct students to place little to no weight on their heads. This better protects the neck, but then you have to consider that most people have meager compressive and tensile loading histories in their shoulders and arms, outside of some planks and possibly pull-ups in the gym/studio. I suspect that loads produced in the shoulders & arms from headstand or handstand far exceed most peoples’ loading histories and capacities. Nobody has studied this that I’m aware of.
The context of fear and empowerment is so important to this discussion. In my early 20’s, I was diagnosed with panic disorder, which was layered on top of a history of generalized anxiety. At age 26, I began rock climbing and that was the beginning of the end of my battle with anxiety. Climbing for me was terrifying, but I persevered (main motivator being I was totally in love with the guy who was taking me climbing:) and through overcoming my fears of heights, hanging belays, run outs, and dynos, I overcame my fear of life. Climbing is inherently dangerous, but 99% of the danger can be mitigated by good choices. What I’m learning about headstand (and shoulder stand) is that even the best choices (alignment, good instruction, acquiring strength, etc.) may not protect you from accumulated damage from putting 50% or more of your body’s weight onto your cervical spine, unless you are levitating your head, which I suspect most people aren’t. Listening to your body and doing what is right for you, while in most cases is sound advice, may not override the truth of biomechanics when it comes to standing on your head.
Reply to J.
I applaud you for recognizing your “youth” as a teacher and putting your student’s before your ego. I wish I had showed the same restraint. It took me a while before I realized that just because I can do a headstand, arm balance, etc., it doesn’t mean I have the maturity in my practice to teach it. And, for what is now paramount to me, it does not mean that I understand their impact on biomechanics well enough to be teaching them to students, whose movement and loading histories I don’t know well. I’m not sure, though, if “feeling good” is always a good marker for the safety of a posture like sirsasana. Much of what I’ve read in the case studies and in the personal stories of long term yoga practitioners discusses cervical spine injuries as more chronic or cumulative in nature – not of the burst fracture type – but of accumulated damage from unnatural loading on insidiously degenerating discs and bone density-compromised vertebra. Most of these practitioners “felt good” for those years they were doing sirsasana, until they didn’t.
Reply to H.
You are right; the Hector study did not look at duration in headstand as a risk factor for cervical injury. However, earlier studies of headstand related to glaucoma found that duration positively correlates to increased intraocular pressure. I would posit that greater duration would be associated with fatigue, thus disrupting ecological balance between arm/shoulder forces and head forces. Your advice to students not to kick their legs up in sirsasana, and to work on having the strength to weight ratio to lift them in a controlled, symmetrical manner, certainly aligns with Hector’s study. As for shoulder stand…. it is another posture that has not fared well in the medical literature…more to come.
Reply to a different M
Hector’s study showed repeated loading of the head and neck due to intrinsic bouncing and weight shifts between the arms and head. Unless you were completely levitating your head from the ground (were you?), it seems like you would be unable to completely remove loading forces from your neck. I would love to hear your technique.
Reply to R**
I edited my post to say the following: “I’ve been in many yoga classes, where headstand was cued, but few of them came with warnings about headstand’s potential effects on glaucoma, detached retina’s, neck issues, or uncontrolled blood pressure.” I appreciate the feedback that helps me to clarify what I really mean.
** R is a former teacher of mine and has reached the Intermediate Junior I level in her Iyengar teacher training, which is frankly badass in the exquisitely rigorous training curriculum and testing process that is Iyengar (don’t let “intermediate” and “junior” fool you, this is a remarkable accomplishment). Originally, I said that I had never had a teacher give contraindications for glaucoma, when instructing sirsasana. R challenged me on this. I have taken classes/workshops from a handful or formally trained Iyengar teachers but it has been some years and I don’t recall these contraindications, but I don’t trust my memory either. However, in recent memory, in local and regional studios in the last year or so, I can remember specific times when the warning was not given, because I was listening for it. That is a more fair statement.
General reply to all
I wrote this article from a teacher’s perspective. But as a student/practitioner, I have a different relationship with the King. Ironically, I used sirsasana as a therapeutic exercise (protocol of Loren Fishman that I referenced in my article) after I tore my labrum from the bone and partially tore my supraspinatus showing off in downward dog. I credit sirsasana with my near miraculous, almost full recovery.