Quote Originally Posted by R2L View Post
often when you first put a dog on a springpole, his jaw area will start shaking when u get him off.

muscles, that can be trained ^^

jmo
Completely agree with you, also some dogs jaw will shake and the dog will start to loose it's grip, when you first give them bite work. But as time pases and you give them more bite work this stops happening, I guess it's jaw muscle is being worked out, like Jack said, it's the equivalent of a boxer hitting the bag.