The practice of Jālandhara Bandha requires the practitioner
to keep the spine straight, the head will be slightly forward.
So draw the head back as well, as it tends to come forward,
ie the centre of gravity in the head moves forward of the body.
If set right you will feel a little contraction in the abdomen.
So, align the spine up, draw the head and neck back, and tilt
the chin in, though not to the throat, the chest or to the heart.