QUOTE(meerkat @ Jan 6 2006, 05:00 PM)

When I played as a child I don't remember my arm hurting so much! My bowing arm generally gets me through a piece, but is aching by the end of it. I get through my half hour practice by having little breaks between each piece. But it's pretty sore! And by the end of a practice session, I'm bowing more carefully because it hurts, and that's making me more screechy. It's not agonising or anything, and I'm not getting pain after a practice session - it's just during.
My teacher said that my bowing was pretty good, and that my grip and technique were sound. But I wondered whether you thought I might be doing something to contribute to the soreness (largely in my upper arm and shoulder). Or is it just a case of using muscles that, old and lazy as I am, haven't been put to much use recently?
It sounds as though it might be a tension problem. 'Grip' ? There should be no 'grip'. The hand/thumb need to be in a good posiiton on the bow, but you shouldn't be gripping. One trick is to imagine yourself on the deck of a ship and to lift you hand an place it on the rail. You wouldn't grip would you ? (I'm talking calm waters; not stormy ocean

) you'd be surprised what a knock on effect gripping with the thumb can have.
Try sitting in position with your 'cello but not playing. Just be aware of your shoulder, arm, elbow, hand alignment, and if you are aware of any tension at all, consciously try to relax. Perhaps play a while, then stop and check if any build up of tension is occuring. Also stop and check your sitting position and the way you hold your cello.
I'm afraid that's all I can suggest at the moment.

Hope it helps.
EDIT: I've just read your other 'cello post. Your 'cello might have somthing to do with it ! A warped neck and too high bridge is not going to help matters !
All the best
iona