In the unity of shoulders, neck and head, the small neck muscles and multisegmental longer neck muscles play a crucial part.

You can check for their function putting your index and middle fingers onto the base of your scull (flat and soft) and start looking into different directions. The muscles initiate head movement once you decide to look somewhere. There are straight and oblique muscles, so each direction can be served.

Those muscles tend to shorten when people have a less-than-optimal posture - i.e. if your shoulders come forward, your back is rounded and your cervical spine is tilted back (I will call it couch-potato-position).

To get out of that position - and in order to lengthen those small neck muscles, you can rotate your shoulders backwards and down, tuck your chin in and you'll instantly feel a slight stretch. Just doing this movement a number of times in between your daily routines will alter the positioning of your head on your spine and lengthen those muscles permanently.

If you want to losen those muscles a bit, imagine a horizon line on which a car is driving back and forth (pictures for download just below). You can evaluate how your head movement is by imagining this car driving EXTREMELY SLOWLY from one corner of your practice room to the other. Then you just pick a small range for the car just in the center of your sight and move your head as if you were saying "no no no no no..." This way, the small head muscles are engaged and ready to let go of tension.