..So, I loaded the gif into GIMP and went through the impact frame-by-frame. The pixelation makes things very ambigous, but he definitely didn't hit his head at full force at least. If you look closely you can see that his body is completely sideways when he lands and that his right arm is underneath him, so the head must have traveled past his entire right shoulder width to get hit. I still think he got some proper whip lash from this, but it looks to me like he just barely managed to muscle his head away from the ground.