Doesn't seem like a good idea to me, since the impingement occurs between inferior AC surface and Superior surgical neck of the humerus. I can't picture a shrug in any direction that would unimpinge the joint with the humerus in anterior adduction. We use the humerus at 70 degrees to unimpinge, and we've never had any problems. This is brilliantly illustrated and explained on pp 157-59 of the blue book.