This intrigues me as a Podiatrist and Tai Chi instructor. I'm having trouble understanding as in a correct bow stance the groin would not crease to the extent that you are indicating...so his posture needs more correction in the video.
What other postures are you stating that closes the Kua?
It is an interesting observation none the less but question whether the Kua would actually be closed in correct postures.
-Colin Power 3/21/12 Comment to http://www.youtube.com/watch?v=aKtbIh0NnRI
Thanks Dr. Power for your inquiry....Not to sure where or how you studied but all postures should have Kua in the Yang Family form(obviously except the beginning and ending postures)The Kua opens and closes as we put the weight on one leg(closed) and as we are shifting(open) to put the weight on the opposite leg(closed) and so forth....Curiously, in my 30+ years of practice and 12 years of China.... I have never heard of a bow stance in Tai Chi, I did practice those(bow,horse,cat,mantis,monkey, T, etc. stances) 40 years ago in my¬ Karate/Kung Fu / hapkido / Ju-Jitsu days....maybe its semantics, recent vernacular, or superimposition?....don't know.....
Yang Tai Chi has its own specific stances, none of which in my humble opinion, could be described as a Bow(and arrow) stance(ie. the weightless / empty leg is never straight)...Im thinking you were not taught about double-weighting....Were you taught by a karate or kung-fu teacher.....studied Chen Family style?Since Yang Family Tai Chi is a Yin Predominant¬ art and all about yielding not fighting, there is no need for warrior/Yang predominant stances...
I may address this in a future video(if you have a question others might also)......sadly Tai Chi in America is a watered down version of the original(foundational principles are not taught just like alot of Yoga) Another example is the imitation Chinese food we eat here in the US (I really miss the food in China).....hope you keep watching
PS Wondered what you thought of the applications? Have you learned applications to the movements of the form?
Ok worked out why the Heart rate increased...not magic just science. You have your student in an over rotated bow stance (deliberately maybe) to compress the Pudendal nerve of the groin region. Compression of this nerve is Known to increase the Heart rate and blood pressure because it consists of both Somatic and Autonomic fibres. Hope it was just an honest mistake on your part rather manipulating science to Sell the Magic of Taiji. My Masters degree in Podiatry is good for something :)-Colin Power 3/22/12 Comment to http://www.youtube.com/watch?v=aKtbIh0NnRI
No Mistake / No magic (im versed in the sciences also)....My goal is to show interested and open-minded people that the "science" of today corroborates what the Taoists said(many times without detailed explanation) and did thousands of years ago without the aid of dissection or microscopes....I was going to talk more about the science in further videos but now I guess is the "teachable moment".......Hope my anatomic knowledge can better explain the mechanism of the Kua in Tai Chi(doctor to doctor)....Actually the compression happens to the femoral artery http://www.bartleby.com/107/Images/small/image549.jpg .... not to the pudendal nerve http://en.wikipedia.org/wiki/File:Pudendal_nerve.svg (which is far too interior to be affected much) If we were talking nerves it would be the Lateral and Anterior cutaneous nerves.... but nerves have a miniscule role to play in the Kua concepts however they have a primary role in acupuncture. ....Focused compression of a nerve would have been difficult to do without assistance, caused numbness and weakness in the legs(loss of function) and would have been difficult anyway without some sort of external pressure(ie. the Common fibular/peroneal nerve when we cross our legs for an extended period)....
Taoists didnt know anatomy like we do today but they knew what worked...they were tapped into the universal knowledge that comes from daring experiments and original thought not preconceived notions, reductionist ideology, or western scientific method.........
Returning to the science / physiology of the Kua topic..... blood pressure / heart rate increase is a response of the hypothalamus and to some degree the amygdala to the occulsion of the femoral artery http://1000awesomethings.files.wordpress.com/2010/11/femoral-artery-e1290384324238.jpg?w=156&h=276 (in the center of the Kua) caused by the person using kua to its fullest extent(more kua more occlusion...committing to one leg).....This closing and opening¬ of the Kua is the subtle "magic" that the west cant understand and so we see few people in the west study Tai Chi....The Kua is key to the hidden aerobic component of Yang Tai Chi......I hope to remedy many misconceptions(like the above) with my videos.
For example, in Thai massage there is a technique called "Leg Blood Stop" where the practitioner palpates the femoral arteryhttp://www.aclandanatomy.com/images/videoTnails/abstract_2-1-14.jpg¬ and then places their palm-heel on that area and translates pressure to the area by raising the body(kneeling push-up style)....as the blood flow is reduced to the lower leg the hypothalamus is afferently notified and it increases heart rate to try to relieve the obstruction hydraulically (by an increase in the rate and amount of blood flow)....after 30 seconds the therapist feels the pulse increase dramatically and the palms are quickly¬ removed .....Immediately a strong rush of blood is felt by the client as serum under higher pressure and speed travels inferiorly finding its way to and perfusing even the smallest capillaries thus reducing pain caused by ischemia whether it be mechanical or chemical(Warning: this technique not recommended for those suffering from Advanced Diabetes II, HBP, CHF).
This works well on borderline diabetics and people with cold feet/poor circulation....(maybe as a chiropodist your patients would benefit from this technique and using Kua in the form---I know many people that do)......this technique was first used in Thailand by the Buddhist monks to bring their legs "back to life" after long hours of seated meditation(ie. Thai massage is their national healing modality...not drugs and surgery).....Finally, sorry to disappoint but my student was not over-rotated ....he was fully committed to his support leg(single-weighted)..... from your postings I presume you studied US tai chi and are under-committed to one leg when you practice(ie. w/o kua / double-weighted / bow stance or you wouldnt have asked....right?)....no worries that's a common sophomoric mistake in the "Way" of Yang Tai Chi.........hope this helps in your journey......Dr. T