We comfort babies this way, rubbing their backs. It helps to bring the parasympathetic nervous system online (the relaxation response).
I remember that for 6 months during my early therapy, I had that urge for someone to rub my back. I think I was coming out of dorsal (a shut down state of arousal). I wish my therapist had had the courage to do this for me.
Thanks for your comment,
Shrinklady