ppko said:
any sport is not realistic but if you do katas the way they are meant to be done they are very realistic.
No, they aren't. They are a good library of techniques, they are a good cardio workout, and they are a good way to reinforce the basics. But in no measure are they a good way to train realistic self defense.
Take for example, the first pattern I learned in TKD, the four directional punch. First move is a step out to a forward stance with the right foot and a mid section punch with the right hand. Then a turn to the left into a low section block. Then a midsection punch, low block, punch, block, and so on.
It's a good way to reinforce the techniques of a mid section punch and a low block and changing stances. But the actual string of movements together into a linear pattern is, for self defense, counter productive. Doing a midection punch then turning into a low section block is going to get you in serious trouble unless your opponent is standing right in front of you with his guard down, and the second opponent is standing to your left about to do a low section attack to the left hand side.
Since you wont be moving like that in self defense, why train that way? I use patterns to help keep the techniques sharp, but I certainly don't consider it to be dedicated self defense training. If you aren't going to do a right handed punch followed by a left handed low block then practicing these moves for self defense will actually hinder, and not help you. Self defense training needs to be against live resisting opponents, and it needs to make heavy use of scenarios.