Parivrtta Janu Sirsasana is balletically beautiful, in my view. I love the way movement into the pose takes me into unfamiliar territory. Think about it. How often in the course of a day or even a week would you rotate your spine, and after having done that, then revolve around that axis and bend laterally. The complexity of the pose means it can’t be done perfunctorily. Its path is always going to be uncharted.
The drawing above shows an advanced version. An experienced practitioner will continuously find the pose challenging as it calls for bringing the scapulae and dorsal spine into a finely calibrated backbend.
Novices meet the various challenges of the pose by holding a strap onto the straight-leg foot. They won’t hold the pose for as long as the experienced yogi, but instead repeat it several times and reap the benefits. It’s helpful to do the pose seated against a wall, as it reminds one to move only laterally and not into a forward bend.
One day when I was practising this pose in a group, I got competitive and ended up pulling an intercostal muscle. The strained muscle slowed me down considerably for a few painful days and limited my breathing, so no side bending. I recovered, but it took a few weeks all up; however, the injury in no way diminished my love of this invigorating pose.