Info about "Uraken video"
Uraken (back fist) is a Karate hand technique, one of the fastest fist available. As it uses a snapping motion rather than a thrusting one, (like most other strikes), it can be whipped out in a flash. So why is it not used more frequently by martial artists.
Well it is a technique that relies heavily on the striking point to achieve the best results. You must use the actual back part of the knuckles to strike. Seldom people strike with the padded hammer fist or the back of the hand, which will not do much damage at all, but a strike with the knuckles to targets such as the eyebrow or upper lip can be very painful.
Also when wearing gloves, it is impossible to strike with the boney knuckles, and many fighters tend to disregard the technique because of this. Kyokushinkai fighters although, (who fight without gloves) should use the technique more often. A hard strike in between the ribs can be very painful indeed.
[From markstraining.com. Original page is here]