Parivrtta janu sirsasana (revolved head-to-knee pose)—I could easily write an infomercial for this asana, which might sound something like this:
"Revolved head-to-knee pose is calming as well as invigorating. It's both a relaxing twist and a mood-lifting shoulder and chest-opening backbend, and it provides the soothing hamstring stretch of a forward fold. But wait, there’s more! The diaphragm muscle itself is strengthened by the asymmetrical challenge of this asana. The deepening of breath in the expansion of the side of the rib cage and the compression in the other side of the trunk increase core mobility and soften the connective tissue around both the organs supporting the immune system and those of elimination. Yoga teachers and practitioners alike praise this asana’s calming, stress-reducing powers, and if you try it now, it may even benefit your meditation!"
Are you sold on parivrtta janu sirsasana yet?
It’s a good idea to warm up with some all-around spinal movements like circling the spine from cat/cow; a nice hamstring stretch in supta padangusthasana (supine hand-to-big-toe pose); some standing postures like (side angle pose), (triangle pose), parivrtta trikonasana (revolved triangle pose), and prasarita padottanasana C (standing wide-legged forward fold with hands clasped behind you); as well as walking the hands to one foot and then the other in a wide-legged standing forward bend (parsva prasarita padottanasana).
Revolved head-to-knee pose is an asana you’ll move into slowly and progress with gradually. Modifying to your level along the way makes it an even greater “value.” If you are currently pregnant or experiencing back pain, a simple side reach (not catching hold of the foot) in a wide janu sirsasana is best for now. It's generally recommended that those with C-curve scoliosis stretch the concave (shorter/tighter) side of the body longer than the convex side (the side that's rounded outward). This also applies for those who don't have scoliosis and are simply tighter on one side of the body than they are on the other.
Sit tall in janu sirsasana with your legs wide, like upavistha konasana, but with the sole of your left foot in, toward your right inner thigh. You may be more comfortable sitting on a folded blanket which will tip the pelvis forward and prevent your low back from collapsing. With your spine still upright, rotate your chest toward your bent (left) knee on an inhalation and lift your rib cage up, away from your pelvis. Take your right hand to your left thigh, exhale, and twist to the left, focusing the twist in the upper torso as you open through your chest and rib cage.
Inhale as you bring your left arm up, alongside your left ear. Exhale as you bend sideways to the right, pressing down into your bottom arm to allow your chest and face to rotate upward. Your right (straight leg) knee may need to bend a little if you’d like to try to link your left hand to your right outer foot. Or just enjoy the openness in your left ribs and allow your left arm to arc gently in line with your left ear. If it's in your practice to reach your right outer foot, you can bring your right hand over to join the left on either side of the foot. If you lose some of your rotation in doing so, or if your breath becomes ragged, return to the bottom hand reaching across the body.
Parivrtta janu sirsasana can evolve and expand with longer holds; 5 to 10 smooth breaths here may leave you feeling a sense of calm, or a "delightful buzz" (as I like to call it), which means the vagus nerve is telling your body that "everything is going to be just fine."
Inhale as you come out slowly, and enjoy the moment. Between sides, rest in sukhasana (easy pose). Pay attention to changes that occur in one side of your body before moving on to the other side.