Janu Sirsasana: head to knee, or not? A note on forward bending.

Recently one of my students asked me a question about janu sirsasana. She had watched a certified teacher on youtube, and the instructions of how to do this pose had confused her, as it suggested that janu sirsasana is different to pascimottanasana in that the back is rounded, with head to the knee- which is different from the way I teach it.  Here is my answer:

Guruji couldn’t really speak English so his instructions were very basic.  He would say to stiff people: “head to knee, touch” and push your head down with his hand.  This is a very basic instruction for a beginner who needs to stretch and open.  The emphasis was to open up quickly, and for this, this technique is very effective.  A stiff person would find that before long, their head would be on their knee.  Often in Ashtanga it’s about priorities. First priority if you are stiff is to touch head to knee. Once that is achieved, second priority- nose to knee, then chin, once that is achieved one can move the chin forwards towards the feet, and think about refining the pose further from there.
Pascima means back, and uttana means extension (pascimottanasana).  The emphasis on Pascimottanasana is to stretch the back side of the body, from the feet, through the backs of the legs and back to the crown of the head, and to extend the trunk forwards, whilst keeping the legs and pelvis firm / supported, creating supported space in the organic body (abs, lungs, etc).  The chest should be as it is in Samastitihi or Dandasana (like any pose), i.e. head in line with the spine, chest open, sternum moving forward balanced by the xyphoid process moving down towards pelvis.  The Chest has to open and broaden, the front supported by the back (shoulder blades engaged). The lower back needs to extend, by curving (convex) as the lumber is what gets compressed in life and especially women concave it too much, which can cause back pain and the organs to flop out of the body, forwards, without any support from the body.  This extension is created by keeping the frontal hip bones lifted, the abdomen broad, pubic abdomen lifting with abs broad and soft, supported by the outer hips gripping in, and firm legs/shoulders.  The side body needs to lift up, countered by the spine moving down and into the body.  All of these principles apply to janu sirsasana, with the difference of one leg bent, and what this does to the legs/hips/trunk/abdomen.  If the right leg is bent, the challenge now is to work with releasing the right waist, moving pelvis and the abdomen to the left, so that as much as possible, the hips are square, both sides of the trunk can extend forwards lengthening, and the chest can make the same actions as you would in pascimottanasana, i.e. sternum moving towards feet, xyphoid process softening towards pelvis, shoulder blades moving down the back so the trapezius is descending, and chest opening, neck in line with the spine.  Janu means knee, sirsa means head-the head can go towards the knee, but only if there is a sense of extension in the trunk. The left thigh has to stay upright so splitting/broadening the outer hamstrings and pulling them out with your hand will put the top of the thigh in the right place (there’s no point moving the top of the thigh if the hamstrings are not broad, it will just slip back to where it came from)- the position of the left hamstrings/leg will affect the position of the chest/abs over the left leg and if the leg is in the correct place, this will feel easier and soothing to your abdomen and breathing.  The bent leg thigh needs to rotate outwards as in baddha konasana, knee and thigh moving towards the floor, with the shin rolling out in opposite direction, shin facing the ground, as in siddhasana.
As a rule of thumb, you can think of the following for most postures except for the arm balances (where the spine/chest must curve/convex): how would my posture (chest) look if I was to keep it as it is in this position I am in now in this pose, and stand in samastitihi or sit in dandasana?  Is that the default posture I want to have in life ?
Asana, as well as cultivating peace of mind, is for the health of the body and mind – to train the body’s neuronal pathways to recognise how to hold the body in the optimum position for wellbeing.  When the lungs have more space, and my chest is open, better oxygenation happens with all its knock on benefits, I feel better, more comfortable in my body, and an increased sense of wellbeing.  When I compress my chest, curve my shoulders, I feel the opposite.  Science is now finding that posture and state of mind are linked-open chest promotes positivity and slouching promotes depression and vice versa (i.e. depression makes one slouch, positive feelings makes one stand taller/more openly).
But I would really urge you to test all of this for yourself, and make your own decision: which way feels better? Which way is most soothing to your nervous system, your breathing, your mind? Which way engages the right muscles to train your body to hold itself in a supportive position when you’re off the mat?