Yeah it happened one year to me and I did it to the point of popping my shoulder, thought I popped it out of the socket for a moment. Hurt like hell and took me quite a while to get it to feel right again. A lot of guys in this weather make it a habit of pulling back their bow every so often, maybe every hour. Good idea, esp if you didn't pull it back once since you were out. I thought maybe it mostly happened because of the extra clothing binding up my shoulders that time. Hard to say but the cold sure had something to do with it as well.