I have always considered it bad policy to land on my head. I try my best to avoid doing so. The head is just not structured to bear the weight of the body, or to withstand more than an occasional semi-violent thump. The soles of the feet, on the other hand, manage this quite well. I have jumped from a few moving vehicles in my day, and let me tell you, the head is just a frightened onlooker in such instances.