This piece is abstract but, in order to capture the gesture I really have to understand where the musician is exerting his energy in regards to how he holds the instrument. I found the below link online that talks about the proper way to hold the bow. I also researched how to hold the violin. It is held with the chin and chest leaving the fingers the ability to move up and down freely.
http://www.singingwood.com/violin-bow-hold/HowToHoldTheViolinBow.html
The fingers that hold the bow.