'This book, representing the system of of vinyasa krama contains a progression of vinyasas. In each sequence and subroutine, the flow progresses from the simple movements to those that may appear impossible at first glance.' pXX
Each asana within a sequence can be seen as preparing you for the one that follows. Problems come when you take a portion of a subroutine from here and part of another from there and so on, building up a daily practice routine or in the case of Ashtanga a series. Unless you want a four hour practice you're going to end up losing some of the preparation poses for some of your chosen asana, can't be helped.
I've always felt this to be the case in Intermediate series. Kapotasana is immediately proceeded by six progressively deeper or at least less supported backbends. How different that is from the first Leg behind head posture Eka pada Sirasana. It's been put to me that if you follow the modern Ashtanga approach of adding Intermediate poses to Primary, one at a time, by the time you arrive at practicing LBH you will never have another problem getting straight into the posture. Perhaps that's true for some, sitting here in frount of the Mac I've just put my leg behind my head, cold and it's true I'm flexible enough to do it. However, I personally find that if I have had some LBH preparation poses I can get my leg further over my shoulder, I can get deeper into the posture and feel more comfortable while I'm there.
So, while I seem to be back following a traditional Ashtanga practice again, I do occasionally, add a posture or two, here and there, where and when I feel it's appropriate. That's not traditional you might argue shaking your head in despair and/or wagging your finger in displeasure. Whereupon I might choose to direct you to this quote form Manju Jois
6. Which was the type of practice your father asked you to do when very young? Did you practice the normal Ashtanga Series or something adapted to your own capacity and age?
At the beginning I could make the postures that I wanted to do. He was not too strict when I was 7 years old, he let me do only the asana that I wanted, but when I started growing up he slowly got serious and he wanted to be sure I learned in the right way. Then I had to practice yoga in his presence in order to be sure that my bandhas were right, my Ujjayi breathing was right, my postures were right. Then he started to give me postures and if I couldn't’t make one he gave me another one to try. That helped me to master the postures. He never told me you have to stop here because you have to master the posture before passing to the other one. He always encouraged me to go other way round in order to master the posture. And this gave me a lot of flexibility that helped me a lot and yoga should be taught like my father did with me.
IN THE FATHER’S NAME
Interview with Sri Manju Jois
By Giuliano Vecchiè
Flexibility, that pretty much sums up Krishnamacharya's later teaching, as presented by Desikarchar and Ramaswami, could it be that he was teaching flexibility back in the 30's and 40s in Mysore when SKPJ was his student.
Here then, as promised, are some LBH preparation poses that you can slip into your practice as you see fit.
Leg behind head postures appear in several Vinyasa Krama sequences
In the Asymmetrical sequence Eka Pada Sirasan is preceded by
Arkana Dandasana (Archer)
and Kraunchasana (heron )
In the Supine sequence Dakshina Bhairava or Kasyapasana is preceeded by several leg stretches but this one in particular.
In the On one leg sequence there are several leg stretches also including Trivikamasana (conqueror), sorry forgot to take a picture of this one, mine's pretty lame anyway so your not missing much. These are before Durvasana (standing leg behind head).
In Ashtanga's Primary before Supta Kurmasana, we have of course
And while practicing some Yin Yoga the other evening I came across these two which make great LBH preparation poses.
Eka Pada Rajakapotasana Variation
Utthan Pristhasana Variation