From The Magic of Somatics, this maneuver quiets pain at the front of the shoulder and side of the neck: pectoralis muscles and sterno-cleido-mastoid (SCM) muscles. It takes you progressively out of the tension pattern of Startle Reflex. (See http://somatics.com/hannart.htm.
The key to this movement is to synchronize the movement elements. That means the lifting movements of the head and shoulder, and breathing.
You use your breathing to pace, that is, start and end, the other movements. Your breath is also what helps you to let go of your pectoral (chest) muscles, so your shoulder can move back (posteriorly).
Be careful to lift only one shoulder at a time; whichever shoulder you lift, you rest and brace yourself upon the other shoulder.
Startle Reflex is a protective action pattern triggered by fear — closing up the soft front of the body. Habituation in this reflex restricts breathing, causes elevated heart rate, and forward head position.
The Magic of Somatics, page 37 | http://somatics.com/page7-somagic.htm
Clinical Somatic Education: A New Discipline in the Field of Health Care