Some hold this pose on the above picture for 5 breaths, but it's thought only for transition. It can make sense to hold the pose longer because one can work on stretching the upper body. moving the shoulders backwards and feeling comfortably in that pose. The challenge is when moving forward that the back remains straight. This got better in my case.
Leg behind head poses seem to be important in Ashtanga yoga. The first very deep legs behind head pose is already in primary: it's supta kurmasana. I was able to do supta kurmasana when I practiced dwi pada sirsasana, the next pose. Most people can only cross their feet behind their heads and not in front of it. It requires very long legs in order to be able to do it. The earlier one can start second series, the better. P. Jois didn't stop people, he pushed them through first and second. He taught as many asanas as possible very quickly. I learned this from the book "Guruji".
My trick to learn it: Try it in the evening on the bed. Lie on your back. Bring the knees next to the body on the mattress. The soft ground makes it easier than a floor. Be patient.
For your own safety: Think to bring the knee back. The foot shall be rather next to the face, then bring the foot behind your head. To bring the foot from before the head to behind the head is a long way. Take care.
My next steps:
- the vinyasa needs extra attention
- I try to bring my foot more down on the back. This is also necessary for asanas to come.
- to keep the upper body upright is also a goal.
Today is Thursday: I'll practice primary and I'll work on third series. This is the plan. I also feel fit and ready for it.