Is this correct?

[ps1]

Hey everyone. I'm no TKD expert. I saw this video and was wondering if it's correct that they all bob up and down throughout the form. The reason I ask is because (as a general rule) in most karate kata, that would be a mistake.

[DWx]

Bobbing up and down or "sine wave" is usually an ITF/G. Choi thing. The idea is that you relax your muscles causing your knee to drop and then you rise up and finish with a downward motion. Loads of arguements of whether it works or not or whether it has any actually use. This article goes over the main points comparing it to the usual hip/snap method of power:

http://tkdtutor.com/06Concepts/Power/HipSnapWindingSineWave/HipSnapWindingSineWave01.htm

It tends to get over exaggerated in tournaments or sometimes people do the movement slightly wrong creating a saw-tooth shape rather than something along the lines of a sine curve. General Choi explaining how it should be done:

Hope that helped.

[ps1]

Thanks for the info. Just wondered whether it was poor technique. It would seem that they are performing it correctly for their system.

[bushido_man96]

The sine wave continues to be a curiosity, I think. I practice the same system of forms that Gen. Choi designed, but without the sine wave.

I think that the sine wave, done properly, is supposed to facilitate what is basically a "body drop" or "gravity drop" upon completion of the technique. The body drop uses gravity to drive more power into the finish of the technique.

As you can see, from watching various videos of ITF forms competitions, and the one of Gen. Choi that DWx has displayed here, you can see that it appears that many exaggerate the motion too much, thus making it a detriment to power, combinations, speed, rythm, and timing. Even Gen. Choi's explanation is a bit confusing, and very brief, with only a few examples that he demonstrates.

As for what you mention about the Karate Katas, ps1, I have seen something much related to this. In reading Nakayama's Best Karate series, I think book 2, Fundamentals, distinctly shows what looks kind of like a sine wave motion of moving the body for a lunge punch, and describes it as incorrect. However, this is to be expected, as I feel that the introduction of the sine wave was soley that of Gen. Choi, being a distinction he was trying to make between Karate and Taekwondo.

Now, allow me to get more long-winded, if you don't mind. I will not totally discount the usefulness of the sine wave. However, I don't fully endorse its use, either. Many times when I watch ITF forms videos, they just seem to lack power and fluidity, because of the sine wave. Again, I believe that most of this is due to the fact that the sine wave may not be taught properly. I think that it is more likely suppose to be a much more subtle nuance of movements.

Again, since I have not much experience with the sine wave, I could be way wrong. However, since it seems to be such an enigma, I choose not to work with it too much, because that would be a disservice to whoever I would teach it to.

[ps1]

I tend to agree with you Bushido. I think it would be useful if you had the time or positioning to utilize the movement. However, it doesn't seem practical to do with every movement.

From a physics perspective, however, I think it would take away from the forward driving force produced by the legs. That force would be used to go up instead. Would the small gravitational forces make up for this? I wouldn't think so.

[bushido_man96]

From a physics perspective, however, I think it would take away from the forward driving force produced by the legs. That force would be used to go up instead. Would the small gravitational forces make up for this? I wouldn't think so.

As long as you control the upward motion, and it is not overexaggerated, I think the it could be beneficial. The problem I see is that it always seems overexaggerated, and therefore, not very useful. When you stand almost straight up, and then settle into a technique, I see the driving force of the legs decreasing, like you mention.