How would you respond to this?

[evilgollum]

On another forum I was explaining a shotokan karate side thrust kick (yoko kaekomi). I'm not sure how to explain in scientific terms of physics how the hip rotation adds that extra "shock". Could anyone help me out here? Thanks.

Here is what the other guy told me:

That kick is used in a lot of arts, mine included. What I'm saying is the rotational force does not contribute to the power of the kick because the final thrusting motion is not at a tangent to the circle that represents the direction of rotational force. You generate a lot of momentum while spinning, but it all stops when you come to that 180 and thrust out perpendicularly to the angle of momentum. See attached diagram.

http://www.paulromerproductions.com/images/diagram.jpg

Edited January 29, 2006 by evilgollum

[P.A.L]

what is the part written in intalic?

[TheAnimal]

In perfect physical theory, that is true. If the kick isn't a perfect ninety degree tangent, then the spin would likely add something to it. However, one must consider not particle physics, but mechanical systems (i.e. the human body!) and then ask themselves if spinning doesn't completely ruin the kick, etc.

For example, in theory, a thai kick would be more powerful if you chambered your leg and kicked not only with the rotation of your hips, but with your quads as well. (Think of a hybrid between a TKD kick and a thai-kick.) Theoretically the combination of forces would be greater than either alone. But in reality, chambering the kick ruins the thai-kick style, and is less powerful, because of the human mechanics involved.

...um, does that make sense?

[Sensei fighter]

Even theoritically rotation will give the kick a bunch of kinetic energy (of course if we consider uninterruptable movement).

On the other hand if a stop takes place on the route of the leg - there is no reason at all to perform such kind of a kick - it's a simple waiste of time. The power of that one would be equal to the power of closer leg performing the same kick without additional movements.

[angus88]

You can certainly feel the difference between just standing there and doing a side kick vs using a hip rotation or other form of chambering for your leg, which acts as a kind of wind-up before the kick. Of course the hip rotation could also be a fake roundhouse leading to a side kick.

Incidentally, and this is directed to "The Animal" - what do you mean by a TKD kick or a Thai kick?

[TheAnimal]

Well, when I refer to a "tkd kick", I mean the kind where your foot is chambered. That is, where you bend your leg backwards at the knee, bringing your foot closer to your butt, basically. A thai kick is one where you bend your knee some, but you turn your hips over as you kick and swing a dead leg into your target, without using your quads to extend your leg hardly if at all.

I hope that makes sense (if it doesn't just say so).

[Bleeding Lion]

I havent done physics for a long time so i wont go into purely theoretical concepts, but I'll provide similar examples in totally different activities.

Ever opened a bottle of wine with a corkscrew? the twist motion helps the corkscrew go further in the cork.

Ever played pool (billiard)? Many professional players perform breaks at the begining twisting the queue at the end of their motion when they are about to touch the cue ball. It gives you extra strength.

Again, those are just examples that illustrate the principle at the origin of the hip motion for a front kick. Ask him to try it by himself, a kick with and without the motion.

[TheAnimal]

Those are actually unrelated things.

[TheAnimal]

you know the more i think about it, the more i think that the arrow on that diagram should be on the left side of the circle, rather than coming out of the middle. in which case, the circular motion would obviously add something.

[juey palancu]

Hi,

Rotation in yoko geri kekomi? I've done thousands of those and I just dont see where rotation comes into play. Maybe as you rotate to get into position to kick??

In yoko geri keage, yes, there is the large, semicircular pendulum motion, and in maewashi geri, of course, the whole body rotates, but in kekomi its mostly about driving the hip. Well, the body does a pendulum, a short one, but still pendulum and rotation are not the same...

Yoko geri kekomi is a very powerful kick, by the way, but it is a little slow..

any thoughts?

Gero