My new to me 2 yr old lab does not want to go on his back and will struggle (to his death it seems) not to. I only tried once or twice and I respect that he does not want to do this and will not force him. Does this mean that I will have trouble training him? I notice when he is outside and "rolling" in the snow that he twists his body, but keeps his hind feet firmly planted on the ground. So is he afraid to go on his back or is this a sign of dominate behavior? Any comments would be appreciated.