Hey wheres my ko at on that vid I dropped a kid with a body shot through the padding ya i know he probably didnt do situps Anyway van to answer your question in the sport of tkd if you notice most of those knock outs come from a counter spin or other kick. that is the defence there is a counter for every kick and who ever screws up first looses. as far as the hands up thing i think it is just easier to pull off different kicks with that hand possition. but i always kepted my right up but its just a style that is more based on footwork and countering than blocking. really I hate watching kickboxers just take kicks when they could simply take a half step back.