Check out the 2021 Fiddlerman “White Christmas” Group Project.
I found a really excellent seminar by violist Kim Kashkashian, recorded from Zoom last summer, that covers a variety of topics relating to posture and movement. It includes warming up, some mobility exercises, holding the instrument and bow, a little bit of tai chi for string players, and a brief discussion of chinrests and shoulder rests.
About an hour long, worthwhile for violinists or violists at any level from beginner to pro.
Thanks Andrew! I watched this at work today . I really liked the bit about the right arm and the tendinitis.. I think I did get a bit of tennis elbow well I did for a while but it seems much better now. Also agree with mouse about the fourth finger. I have practiced it and I think putting fourth finger down first helps get my thumb in the right place!