Avoid the drawstring effect
Many violinists crunch their shoulders up and their heads down into the violin. This shortens the muscles of each arm and greatly affects sound and left hand facility. It also isolates the arm from the shoulderblade, which is the first bone of the arm.
To avoid this, try the following exercises:
Stand and play with your head against a doorframe. You may feel you have to press backwards with your head in order to maintain contact. Now step away and feel the same backwards, upright position.
In a straight chair, sit with your back against the back of the chair as you play. Maintain contact.
With a partner, take turns holding each other’s heads back. (This is really easy if you have a ponytail!)
Draw an upbow, allowing your head to travel in the same direction as the bow. Draw a downbow, and move your head slightly to the back of the chinrest, in the opposite direction from the bow. Can you feel the slight tug of the string?
Loosening the Head on the Violin
Settle your head into the chinrest gently, balancing the violin with the relaxed weight of your head.
Incorporate Karen Tuttle’s breathing exercises into your bowing: each time you breathe out, allow the head to settle towards the back of the chinrest gently.
As an exercise, play downbows holding the violin with your left hand as you move your head around; play upbows with your head gently relaxing into the chinrest as you take your left thumb off the neck of the violin. Are there moments in your music where you could do one or the other, to release muscles?
Holding still helps your nervous system sort out the fine movements of your hands and arms, because the variables are fewer; but moving releases muscles and combats rigidity. Moving also is often more exciting for the audience. Think of a modern day performer such as Joshua Bell and compare him to videos of Heifetz and Oistrach. My own experience is that it is generally best to move lyrically during singing lines and slower music, with swaying being preferable to the crunch, to keep the shoulderblades as stable as possible; but it is almost always best to have calm shoulders, a stable violin, and a centered balance which allows your weight to drop through both your feet during fast passages and string crossings. It is also usually true that a stable violin produces a stronger tone.
Try fast passages with your violin scroll on a stand, on a ledge, or against a towel on the wall. You will find that shifts and string crossings are much easier when you do not have a moving target!