Here's an overview of the Ashtanga yoga system.
Ashtanga Yoga Index
Basic Yoga Poses in the Ashtanga Primary Series
These move between standing poses and belly down poses.
Then from there the focus is on standing poses, some of them balancing on one foot poses like Big Toe Pose, then seated poses, most of them seated forward bends or hamstring stretching yoga poses, and supine (belly up) poses, followed by some inverted yoga poses, namely headstand and shoulderstand.
A closer look at the actions included in the sun salutations
A closer look at sun salutations shows that they include backward and forward bending spine actions. So for example, the first movement of each sun salutation, lifting the arms, can be accompanied by a backward bend of the spine. Also, upward dog involves a backward bend of the spine. Meanwhile, The second movement, bending forwards, can involve a forwards bending of the spine.
They also include backward and forward bending hip actions. The main backward bending hip action happens in upward dog. Forward bending hip actions occur in the standing forward bends, chair pose (at the beginning of sun salutation b) and in downward dog pose.
A closer look at the standing poses
As for the standing poses, they include a mix of bent and straight knee poses, as well as asymmetrical poses with the legs spread front to back (longitudinal standing poses) and then side to side (lateral standing poses).
The lateral asymmetrical poses are noteworthy because in these poses, triangle and side angle, the hip is bent to the side with the thigh turned out (or if you prefer, externally rotated.)
A closer look at the seated oses
The seated poses are mainly forward bends for the hips. A lot of these are asymmetrical with one leg straight and the other knee bent. But, the bent knee leg is taken through a wide variety of bent knee positions.
These include positions with the shin folded to the inside of the thigh and to the outside of the thigh.
As an example, the first two asymmetrical seated poses are a lotus pose variation which folds the foot to the inside of the thigh and a hero pose variation which folds the foot to the outside of the thigh.
How the seated poses "mirror" the standing poses
If you look closely at the ashtanga primary series with a discerning eye you'll see that a lot of similarities between the standing poses and the seated or supine poses. It's almost as if the seated part of the series is just the standing poses done sitting down.
Neil Keleher is a Systems Design Engineer with a bachelor's degree from the University of Waterloo.
He has taught yoga for over 22 years. He specializes in anatomy related to proprioception and movement.
He illustrates his own anatomy articles.
His classes focus on improving body awareness while at the same time building strength, stability and flexibility.