This is the first position of eka pada sirsasana. It's not held for 5 breaths, it's a transition pose. Nevertheless it can be a recommendation to hold it longer in order to get accustomed to the pose. Important is that the knee is as far as possible behind the body. It helps to keep the leg where it is supposed to be when the foot is pointed. I work on stretching the upper body when I inhale. One can also hold the chin with the hands to have additional support. Patience is necessary. Once the pose can be done, the next challenge follows. By now I've to hold the leg when I move forward into the next positon.
This is the position that is held for 5 breaths or longer. Engaging the muscles is important and stretching the body. Engaging the bandhas help. To come up without holding the leg that is behind the head is the next challenge.
From this position one swings into chaturanga dandasana. It might be good to hold the position for several breaths. In the traditional form it's a transition pose, too.
Not only the poses also the vinyasas are advanced. Intensive breathing comme il faut supports the execution of this asana.
To lean backwards is good.
I repeat this asana sometimes as this pose is still volatile. I also practice it while lying on the back. Being on the back facilitates it. A lot. It's even possible to relax.
A happy start in the new week.
Oh, and if you like my blog I appreciate it if you recommend it to your friends. I'm on facebook, google+ and twitter. Links are on the right side of this blog.