This
maneuver is routinely carried out by masters of following sports: BMX biking,
skydiving, skiing, snowboarding, trampolining,
gymnastics, ice-skating, diving, and by
ninjas.
This trick amazes onlookers because the practitioner defies common sense by letting his or her body rotate before placing his feet on the land once again.
Often, the jump leading up to a flip throws the body in such a way as to make a flip neccessary. While popping off a spine on a snowboard, a denied rotation of the rider can lead to a headfirst dive into the hardpack and a cracked or severed spine. A master of one of the sports mentioned possesses the skill to go with the flow of his reutine to the extent that a flip is an easy ammendment to any pattern of motion.
Along with the ability to be inspired by the dread of failure and to later laugh at the fear you once felt all a master needs to flip is a confident look upwards. Like a horse responding to the pull of reigns, the human body goes where you look, and if you're falling over a jump, looking up brings on the desired backflip.
If you let yourself crumple up midway, your jaw and tummy may meet the landing instead of your feet. This is why novices should avoid backflips from anything but a diving board.