In all of Choi's teachings, and mentioned prominently in volume 1 of his encyclopedia, he teaches the concept of "Theory of Power". The author that Jas Key mentions (Dan Djurdjevic) dismisses the idea and gives good reasons why it should be dismissed. His answer might be fine from perspective of a Karate-ka. But Gen Choi's theory on self-defense is very hard, very brutal, and concepts that we study in great detail in Japanese styles, are not common staples in many ITF schools.
In other words: the sine wave contributes to the theory of power, which is that the movements must come from the whole body, and if they come from the whole body, then the body must be rooted. Otherwise, transfer of power would follow Newton's 3rd law in a bad way (in that the body bounces back, rather than transfer forward into the target).
That we move up and down in a natural way is part of the sine wave concept, because we do tend to move in up/down fashion. ITF exaggerates the up and down, but emphasizes that the strike occurs when fully rooted to the floor.
Japanese stylists prefer to take a softer approach, and rely on speed than force, they say. But ITF and Japanese stylists both agree, though in appearance, they seem on opposite sides of the same coin. As beginners of Karate and TKD, we try hard to strike with force and speed. That is why we often have breaking and strike heavy bags and utilize full-contact fighting. As we get older and more experienced, we realize that such force is not needed, and we begin to soften our techniques. You can see this progression when you look at our forms - particularly WTF forms.
Keumgang poomsae, for example, represents a mountain - with imagery of strong and forceful techniques (we tend to forget the graceful balancing and whip turns which require delicate footwork...), but the stomping and upward thrusts suggests very powerful movements. And 3rd dan's Taebaek is generally considered one of the more physically demanding forms we have. Now move over to the other end of the forms spectrum: 8th dan's Hansoo and 9th dan's Ilyeo. These forms are expected to be performed by those in their 60's and up. You don't see jumping and flashy kicks, and anything that requires significant dexterity. The movements are generally more fluid (Ilyeo is almost all dynamic tension).
What this suggests is the irony that Korean and Japanese styles (perhaps others, maybe; I don't know and haven't studied them) all have this same theory of power, and all have the sine wave. The difference is that ITF is more external (easily visible), whereas in Karate, it is internal (not visible).
Karate-ka (and Dan Djurdjevic, article author) prefer that movements move in a straight line - no bouncing. Taekwondo-in would appear to be really bouncy (a very different kind of bouncy than seen in sparring - Dan Djurdjevic has this discussion completely wrong, by the way). In the self-defense kind of bounce (the sine wave), the natural body movements are up and down, it's just more overt and exaggerated. Karate-ka would prefer to move from point A to point B is as most efficient and speedily as possible; any up-and-down movements would slow the body down. But you can't move from point A to point B without a bounce (which is better to term as a shift in center of gravity), and still, to avoid absorbing the push-back that target imparts on the Karate-ka or Taekwondo-in, the TKD would root himself into the ground.
As to sparring, TKD like to keep their distance because kicking is generally favored. At a safe distance away, though, one's foot movements and intentions are more readily seen. The bouncing hides these intentions, and a good Taekwondo-in will change the rhythm from time to time to keep the opponent from timing the bounces. The drop of the hands at a distance is also natural; no need to block when out of range. Good TKD fighters will raise them when they are inside. With hands dropped and at a distance, the bounding allows to hide the intent to charge in, and the dropped hands allow for sudden movement forward, allowing for momentum to pull the body forward; you can see this at work in slow motion of any video of good fighters.
Keep in mind also that when we utilize self-defense techniques in real life - we don't do them exactly the way we do them in forms. This is true of Taekwondo and Karate. Forms provide the basis from which we execute techniques, but, environment, conditioning, luck, injury, and other factors prevent us from throwing a technique as perfectly as we might do in a form. That is one reason why we don't break out into hyung/kata when we are engaging an opponent in real life. Ideally, the result is near-perfection the way we practice. But it isn't expected that they need to be perfect in real life. Same with sine wave: it's an ideal. It's something we practice over and over, and when we throw techniques at someone, the up and down is part of our nature - karate-ka or taekwondo-in.
If you get a chance, do try to read Gen Choi's Encyclopedia of Taekwondo. It turns out he didn't originally design his forms with the sine wave in mind - that is an afterthought. But he does go into comparisons to "other" taekwondo styles, and to some Japanese and Chinese styles.
As a scientist and an experienced martial artist I do not subscribe to the sine wave concept.It is often used instead of twisting the hips, which is where the power comes from.
Here is where the sine wave concept breaks down:
The equation given in the Encyclopedia of Taekwondo, on page 47 of volume 2 is;
P = 1/2mv2
Where P = power
m = the mass
v = velocity.
However this is not the scientific formula for power, it is the formula for kinetic energy. Not power. Power would be the change in kinetic energy divided by time.
Another formula that has been used on one school’s website is;
P = 1/2mv2 + mgh
Where; mgh = 0 for no sine wave.
g = the acceleration due to gravity and h is the height.
This formula is used to attempt to show that a downward motion affects a horizontal motion. The + sign in the formula indicates that the 2 terms are independent of one another (one does not affect the other), if they were dependent then the terms would be multiplied. This is a valid equation for the total energy of a strike but only applies (when mgh does not equal 0) to movements that have a downward component, e.g. a downward punch or low section side kick. It is an accepted scientific theory that for objects moving under the influence of gravity, the horizontal and vertical components of the movement do not affect each other.
Another correct formula for power is;
P = W/t
Where W = work done;
By eliminating time (making it =1 unit in seconds, minutes etc.), concentrating on the RHS of the equation and using the definition of work you have:
W = F*d*cos(theta)
Where F = the applied force
d = the distance moved and
cos(theta) = the cosine of the angle of movement in relation to the applied force.
A cosine wave is just a sine wave shifted by 90 degrees. For any angle smaller than 90 degrees or larger than 0 degrees cos(theta) = <1, which can be seen when dragging an object along the floor by a rope. When the rope is at an angle it is harder to move the object than if the rope was along the ground. For an angle of 90 degrees (the dropping of the hips in the sine wave movement) cos(theta) = exactly 0. In other words the pure downward motion contributes absolutely nothing to the power generated horizontally.
This is simple physics which is called Newtonian mechanics.
I was in the other side of TKD so I don't know the sine wave thing so much. But I have read an article from a guy that seems pretty knowledgeable. I'll post links to his articles here and you could probably browse through them.
http://dandjurdjevic.blogspot.com/2009/1...
http://dandjurdjevic.blogspot.com/2010/0...
http://dandjurdjevic.blogspot.com/2012/0...
i havent looked much into it at least not as much as possum, but i feel using the sine wave makes you predictable
The one where it looks like they are bouncing. I don't use it, but I just like to learn about things. Please give me better reasons than, "it's looks stupid."
I googled it, but I want experienced martial artists' opinions of it who had a reason for rejecting it or training in it.
I already know it's a science term too if you're thinking I'm in the wrong section.
