Six simple Fundamental Asanas (postures) build the foundation of an Astanga Vinyasa Yoga practice. They are often called “standing positions” because they are composed of six relatively easy standing asanas. Parsvottanasana is the sixth of these fundamental postures.
The six fundamental postures are right at the beginning of every Astanga Yoga practice. No matter how advanced you are, after five rounds of Surya Namaskara A and B, you start with these postures. Here, you carry the rhythm you have set up in Surya Namaskara A & B in a flow from asana to asana. With this solid basis, you are perfectly prepared to enter whichever series you are practising.