The circular movements described below and illustrated above make it possible to obtain a compactness in the body.
a) Circularization of the armpit chests
This point is ESSENTIAL: the shoulder blades descend in the back and against the posterior ribs, the chest opens forward.
In progress, I often see shoulders pointing down and a bump in the back (in principle it goes together) in order to compensate for the lack of strength in the trunk and arms. Be careful this bad placement causes bursitis in the long term. This inflammation of the subacromial bursa should be avoided at all costs for it is very difficult to heal.
b) Circularization of the pelvis
c) Circularization of the legs
d) Legs rotation
These three points go together since they concern the action in the legs. These are the same points as in Tadasana.
The action of the pelvis is well known, one pushes the tailbone down, while the pubis bone rises.
The back of the legs is extended towards the heels while the whole front legs go towards the pelvis.
Finally, the legs rotate on their own axis towards the outside.
These three actions together make the legs compact and strong and make them contribute to lift.
e) Hand twisting
Finally, the simple act of turning out the hands makes allows the shoulders to activate, rolling back and down from the ears. More specifically, the elbows will stick to the ribs allowing more compactness of the trunk.
In conclusion, these circular movements are found in many postures but as Chaturanga Dandasana requires a lot of strength, putting these actions in place to achieve a certain compactness, especially in the legs, will help you to hold the pose and not only thanks to your triceps.