Since I first stated that the techniques taught at my school were based on principles, and that we focus more on understanding the principles that makes things work than the techniques themselves, people have e-mailed me asking me if I could explain these principles in more detail.
Unfortunately, trying to explain many of these principals in writing is very difficult, since many can’t be explained in words alone. However, I will try my best to describe these principles for the “blog” readers, using words, charts and pictures.
Keep in mind though, that in order to sometimes fully understand a principle you have to also understand other principles that relate to it. Most principles aren’t fully useable on their own, and have to be integrated with others.
Trying to explain the principle of Back Pressure in written words and illustrations is almost impossible. In fact, it’s hard to describe—period—even in the classroom. And in my experience, trying to explain “Back Pressure” often confuses people more than it helps them.
Of all the top ten principles in the Yachigusa martial art system, Back Pressure is most likely the hardest to teach. And it is definitely the hardest one to learn to utilize properly. However, once learned, properly executed Back Pressure will greatly increase a martial art practitioner’s efficiency and effectiveness at projecting others.
To be honest, even though we use Back Pressure in many of our techniques, to this day I still find it hard to come up with a concise description: what it is, why it works, or how to practice it. I am still looking for an easy method with which to teach my students how to learn to apply it properly.
The main reason why teaching the principle of Back Pressure is so difficult is that Back Pressure is basically an intangible force. It is intangible in the sense that Back Pressure cannot be seen, and when executed properly the movement that creates the force is relatively hard to perceive. This makes the movements hard for others to emulate.
Furthermore, Back Pressure is definitely one of those forces where “less is more.” Using too much torque/power actually makes techniques less effective. This means that Back Pressure is a principle that can’t be faked or forced; you either do it in the right way at the right moment, or it won’t work.
Now before I continue to try and explain what Back Pressure is let me start by stating what it is not. Back Pressure is NOT Chi, Ki, or some other mystical force. It is an application of science. However, I’ll be the first to say that one could easily con others into believing it is something else; and the truth is that many upper level martial art practitioners do.
However, while Back Pressure is not something mystical, when one is describing it or trying to understand it, one must think “outside of the box” in order to fully grasp the concept.
In the most simplistic language possible, Back Pressure is a specific force that is generated by rotating or sharply twisting the back/hips. This rotational force is used to accelerate one’s opponent— usually in a manner that projects them off balance and to the ground.
It is a circular force that basically moves in a semi-arching circle from point “A” to the centerline of the aggressor, point “B.”
In this photo Subject “A” rotates his back creating pressure to Subject “B’s” centerline.
While the “force” can certainly be felt, this “force” has no real direct relationship to the connection points (arms in picture above) between tori and uke. In other words, while tori and uke might only be connected at the arm, the force that actually makes the technique feasible comes from Back Pressure attacking the centerline of one’s opponent.
Confused yet? If you are, you’re like most of my students when first introduced to this topic. In fact, when I initially discuss the topic with new students, I often get perplexed looks; I often wonder if they think I’m just babbling.
While I do indeed often babble, the truth is that in order to understand Back Pressure one must understand basic “Body Geometry,” and some basic physics.
I’ll get to the physics later, but let’s start with the premise that human body exists on several planes. These planes are commonly referred to as the:
- Coronal (Frontal) Plane – A vertical plane running from side to side; it divides the body or any of its parts into anterior and posterior portions.
- Sagittal (Lateral) Plane – A vertical plane running from front to back; it divides the body or any of its parts into right and left sides.
- Transverse (Horizontal) Plane – A horizontal plane; it divides the body or any of its parts into upper and lower parts.
As you will note, all of these planes share one common trait; they are all located along the midline of the body and intersect on the body’s axis. In addition, one can divide each of these planes into 45 degree sectors in a manner identical to the more familiar Happo No Kazushi (eight directions of breaking balance) diagram. I believe I’ve stated numerous times that Happo No Kazushi is an extremely important science to fully understand.
Thinking “outside of the box,” let’s pretend that the lines dividing each of the three planes actually exist and extend away from the body as in the diagram. Imagine that these lines are rigid (like rods), fixed to the body, and move in direct correspondence to the movements of the body.
In other words, when the subject is standing still these lines are just as pictured. However, if the subject rotates his upper body, without moving his feet, those lines will also move the same distance.
Now, assuming these lines exist and are rigid like rods, they would push anything that may happen to be in their way as the person rotated. That would be Back Pressure.
Of course, in the real world there are no invisible lines that extend from our bodies. So the question I; if there is nothing there to actually “push” with, how can Back Pressure work?
As I was being taught the Aiki arts I was always told that one of the goals of proper Aiki technique was to learn to “blend/flow” with ones opponent. This often meant understanding the concept that when two individuals become connected together the truly become as one. They share a common point of center and any movement done by one person will create a direct resulting movement on the other.
Imagine there are two individuals sharing a common center of balance, which I’ll refer to as the “axis point.” It’s easy to see that if Subject “A” rotates his upper body rearwards to his left side, his right side moves forward a corresponding 45 degrees.
Since both parties share a common axis point, as “A” moves he also pushes subject “B.” The force may not come from the connection point, but since there is a direct relationship between the two subjects, whenever one moves so does the other. The torque of the body from Subject “A” produces the force that creates the movement, and that is Back Pressure.
Now for the more scientific explanation.
Fortunately for me, I have a student who majored in physics at Stanford University and has given the science of Back Pressure a lot of careful scrutiny. Due to his efforts, we actually have a working model we can demonstrate Back Pressure on at the school. Unfortunately, that model won’t work in this format, though we hope to eventually film it and add that to the “blog.” Until then. I will defer to his written explanation.
A Simplistic Model for Understanding Back Pressure
By Spencer Burns
As is traditional in physics, we should simplify the problem until it is almost, but not quite, trivial. The basic model I’m going to talk about consists of two masses connected by a bar. These represent the tori (who applies the technique), the uke (who receives it), and their connection. We want to think about how force can be exerted on the “tori” to cause the “uke” to move in a direction perpendicular to the connection with minimal effort or disruption. The apparent force that causes that perpendicular motion is the “Back Pressure.”
“Zeroth Order” Model
The simplest thing for thinking about the mechanics of Back Pressure is to imagine one of those “balancing man” toys.
Ignore the “man” in the center; he’s just a fulcrum. Consider the two weights on the sides: these are the uke and the tori. When you push on tori, then uke also moves. This is the most basic model of Back Pressure: uke and tori rotate as one around their common center of mass (at the fulcrum).
“First Order” Model
The major failing of the “balancing man” model is that in the real world, there is no fixed fulcrum. So let’s be more formal: the tori and uke are rectangles of width “w” and mass “m“. They are connected by a massless rigid bar of length “2d-w“; that is, the distance from the center of the bar (which is the common center of mass of the system) to the center of mass of each rectangle is “d“. This system has no fixed point and is free to move in any direction.
Naively, we push on the center of tori, perpendicular to the connection, with an impulse “I“. This would make tori move in a line at a speed of “I/m” if he weren’t attached to uke. However, the impulse moves the combined center of mass of uke + tori linearly forward at a speed of “I / 2m” while simultaneously inducing a rotational velocity of “I / 2md“. The instantaneous effect of this is that tori moves forwards at speed “I/m” while uke twists but doesn’t move laterally at all, as in the diagram below.
In a real world analogy, tori just applied back pressure incorrectly and has the feeling of having “bounced off” uke while uke just stands there well balanced.
This is the opposite of what we want; we would like to see tori stay stationary while uke moves. Consider instead what happens if we give impulse Ia backwards on the outer edge of tori and impults Ib forwards on the inner edge, with Ib<Ia. If we balance the forces exactly right, such that Ib = (2d+w)/(2d-w)*Ia, then we have the situation where tori is instantaneously motionless (but rotating), while uke is moving forwards at speed (Ib-Ia)/m—exactly the opposite of the naive case.
In a real word analogy, tori would be simultaneously moving both of his hips in opposite directions with a balance of force such that he can “hit” uke with Back Pressure without having to move or losing his balance.
In other words, the Back Pressure in this case involves balancing a translation motion of uke and tori perpendicular to their connection together with a rotation around their common center of mass in such a manner that tori remains stable while uke is displaced in a crisp fashion.
There are many other configurations in which Back Pressure can be applied, but they all involve similar physics. In each case, the “first order” issue is balancing rotational and translational impulses on the connected uke-tori “system” such that tori’s center remains stationary while uke’s center is displaced.
Like I said at the beginning, describing Back Pressure—especially in this format—is very difficult. Hopefully, between Spencer and I, we have at least started to transmit the core of what we know. Or, I should say, the parts that we have figured out how to explain in writing.
Fortunately, plans are in the works to film and post more details on this principle as well as the other nine already posted. While there is no projected date to complete this project, we should do it by the beginning of the New Year. At least, that’s what I’m hoping for.
Until then, please feel free to ask questions. Or, more importantly, if you have any clearer explanations please share them with me so I can continue my study of this principle.
I realize that almost every Aiki/Budo system utilizes this principle, whether explicitly or implicitly. I’m sure there are many instructors/students who have faced the perplexing problem of verbally passing on this principle. I, for one, would find it extremely interesting to see how others describe/explain this principle.
The article on this blog on the Principle of Back Pressure recently caused controversy after it was (much to our surprise) featured on the front page of the Aikido Journal website. Part of the anger we received was due to the fact that nothing in the “Back Pressure” article gave credit to Don Angier of Yanagi ryu.
That was a mistake on our part, and we apologize.
We had intended to give Mr. Angier significant credit for the debt we owe him, but due to negligence during editing, that section of the original article was not included. Indeed, in the other “principles” essays, Mr. Angier was given significant credit for his help (e.g. the essay on #9 Chains of Motion/Commutive Locking).
Mr. Angier not only provided the name “Back Pressure,” but he also really opened our eyes as to how to understand the subtleties. The way Gary has described it to me is that he had previously had an understanding of this principle on a less sophisticated level and had asked other instructors about it; most jujutsu instructors also had an intuitive understanding of Back Pressure, but no term to describe it. However, Mr. Angier was able to describe it in more detail and give us the language to describe it. So as a named principle, this is not something that was handed down to us from the ages, but we have adapted it because of its importance.
As has been pointed out, if one really wants to understand this principle more deeply, Mr. Angier would be a superior source of knowledge. Be we have found working on this article to be very educational for us and we hope that it has been helpful for others. Our intention has never been to try to take credit for Mr. Angier or anybody else’s work; rather, we are trying to better understand these principles of how the human body moves and share with others our meager understanding.
We are sorry once again for the omission.
March 05, 2007