If you see you are going down, even slow, most people can not help but to stick their arm out to try and stop the fall. That will usually result in a broken wrist or arm. Better to keep every thing in and as they say "tuck and roll". That is one more advantage us fat people have over skinny people, we roll more evenly. Another advantage you ask? Fat people hardly ever get kidnapped plus if a group of people are stranded on a deserted island like in a ship wreck or plane crash the fat people can last longer without a food supply. Yep! Anyway if you think about what you need to do in dire situations maybe your brain will remember and act accordingly.