Physical Training Mar 2008
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Response to a Kinesiology of Fencing and Kendo

copyright © 2008 Stephen Quinlan, all rights reserved

As I read the article “Kinesiology of Fencing and Kendo” by Jonathan Riddle, a number of “Red Flags” were raised in my mind. I don’t know if it is due to my own misunderstandings, but there seems to be some conflicting information between what I understand about Kendo’s Men Uchi and what is in the article. I am hopeful that in writing this response article, that these issues can perhaps be addressed. For the most part I will simply indicate the items that caught my attention and briefly explain why. After each point I end the discussion with the word “Comments?” as I am open to be corrected, countered, or responded to.

I have taken the liberty of using diagrams from the “Kinesiology of Fencing and Kendo” (hereafter KFK) article below to simplify the discussion.

KFK Figure 1

kfk fig1,  Kendo Kamae

  1. Center of mass / Center of motion is in the “Koshi” (hips). The term Koshi refers to more than just what we normally refer to as “hips”, but hips will serve for the discussion. It is often told that the source of motion must be from your hips. As one Sensei explained to me, “if you were to draw a line one the side of your hips and the front, the point at which they meet (inside of you) is your center of motion and where you balance yourself.” The above shows the center of mass well up into the torso. In Kendo, I believe our center of gravity is much lower than depicted. Perhaps this is simply picking-nits on the artwork? Comments?

Figure 2 centre of mass

  1. I am unsure of the meaning of the abbreviation GRF in the diagram. Nor do I understand the caption: “ (arrow down) time on ground. As time (arrow down, arrow right) velocity (arrow up)”. This caption points to the left (rear) foot. A quick parse could be “Decrease/low time on ground. As time decrease/lowers, forward velocity increases.” Comments?

  1. When describing weight distribution and the position of the feet in Kamae itself, the article states: “From kamae, or guard position, the shinai is kept in front and the weight is shifted slightly backwards causing the center of mass to shift backwards.”

In Kendo, the weight distribution of the body is usually described as 70% of your weight is on your forward foot, 30% on your rear. Again, described to me by one sensei “Your rear heel is raised slightly off the floor, enough for a couple fingers to fit under and your front foot is flat, but not rooted. You ought to be able to slip a piece of paper under your front heel.”

Shifting your posture, balance, center of gravity, etc… to the rear is a classic example of how we create “Suki” (an opening) for our opponent. Comments?

Here are a series of pictures that were taken very recently as I was helping a Kendoka at our club with his posture. His upper body’s weight was toward his rear when in Kamae. I took these pictures to help show the difference. The third picture is the two made of the two original pictures combined with a line drawn down through the center of the hips.

Tilted posture (weight backwards)
fig 3, tilted kendo posture, weight back

Straight Posture (weight forward). This was accomplished by a simple pelvic tilt.
fig 4, straight kendo posture

Combination (weight forward / weight backwards) with centerline. With the abdominal contraction/pelvic tilt added while assuming kamae, the hips become aligned with the upper body and the body’s mass balances properly toward the front.
fig 5,  kendo stance

  1. The article states “The reason for ki-ai is to cause a compression or contraction of the rib cage by expelling air, this can add to the force from the chest into the weapon.” Again, I must reiterate that I’m not an expert of kinesiology, however this bit seems to be fraught with conflicting information. The “reason” for Kiai is immense, and real Kiai isn’t something that we “turn on or off”…it simply happens. When we train our bodies, we help develop kiai by yelling. Philosophical aspects aside and looking more towards bodily physics, in Kendo our breathing is to come from the abdomen, not the chest. When we exhale, our abdominal and lower back muscles contract, and our diaphragm pushes the air up and out. “Force from the chest into the weapon” seems to imply the tightening or contraction of muscles that we are stressed to keep relaxed. Comments?

KFK Figure 2

kfk fig 2, jodan kamae

  1. The weight of the body is forward in Jodan as for Chudan. The arms and shinai do have an acceleration associated with them when we move them back/up. However, this acceleration is not needed for the cut. Otherwise somebody who begins a cut from the migi or hidari (right or left) Jodan kamae would be weaker compared to one initiated from Chudan, when they ought to be the same. I’m not sure if the author is implying that this acceleration is used for the cut, but this was simply one of the flags that were raised. Comments?

  2. The article states: “Then the shinai is swung forward vertically downwards, and horizontally forwards for maximum acceleration…” “Maximum acceleration” seems to imply that a large amount of speed, and hence muscle usage, is required. The cut is not made due to us “hitting” the target hard or fast, but rather from a “slicing” movement of the blade while in contact with the target. In Kendo, this cutting action is stylized by hitting the target then moving the blade to “slice” via the forward or backward motion of our body. In Iai, the cut does not have to be fast or hard, you must first connect with the target, and then “slice” it via a proper sword swing allowing the blade to do the work. Hitting fast or hard with a shinai or shinken (real sword) does not produce the same results. Comments?

  1. The article states, “…the same time the shinai comes forward, the foot is accelerated vertically upwards and horizontally forward…” The issue I have here is with the statement “…foot is accelerated vertically upwards…” In Kendo, you do not raise the forward foot vertically as if to “stomp”. Rather, your forward foot stays close to the ground, “skimming” it as much as possible. If your body weight is forward (70/30) it is impossible to simply raise your forward foot vertically; you’d fall over. This vertical motion is only possible if your center of gravity is shifted backward to your rear. Essentially the “70/30” weight distribution gives us forward potential energy which we convert to kinetic energy by initiating a push with our rear foot and extending our forward foot. Shifting our center from any direction other than forward disrupts this process. Yes, there is a vertical component to the motion of our front foot, but it ought to be minimal, i.e., to remove the majority of the static friction between our foot and the floor and allow us to move Comments?

  1. More of a technical note that ties in with the above, the classic “Kendo stomp” is not a result of an intentional strong downward force of the front foot on the floor, it is simply a by-product of landing correctly. That’s not to say there is not a lot of force associated with this…there is1. But we do not purposely raise our foot simply to “stomp” downward. It’s much like clapping your hands. You don’t need a lot of force to make the “clap” if you do it properly. If you clap using only your fingertips or the heel of your palm then it’s a different story. This analogy helps describe the “stomp” of the Fumi Komi style footwork. Comments?

  1. Another issue I have is with the labeling of “lever” and “fulcrum” in the above picture. By definition2, “A fulcrum is the support or point of support on which a lever turns in raising or moving something”. By stating that the left hand position is the lever and the right hand position is the fulcrum it would imply that he right hand is center of motion for the cut and that the left hand is pulling or pushing around that center. The labels ought to be reversed with the left hand being considered the fulcrum during Men Uchi. In fact the entire Shinai ought to be considered a “Third Class Lever”3 if my physics memory serves me. Comments?

  1. The article states “…and the beginning of the ki-ai or shouting of men to cause more tightening of muscles in the chest and ribs to cause more force or acceleration and therefore cause more power produced during the cut.” Kiai occurs at the moment we strike, not before. It is the by-product of our body acting together with our mind and intent. It is simply “yelling”, not Kiai, if we just make noise at a certain time frame. When you pick up a heavy object, the moment you pick it up and you “grunt”(usually without ourselves realizing it) that is kiai. After you’ve lifted the object, your muscles are tiring, and you make noises while straining, that’s just noise coming from effort. A very subtle but important difference. Secondly I have an issue with the line, “to cause more tightening of muscles in the chest and ribs to cause more force or acceleration and therefore cause more power produced during the cut.” All of this muscular tightening in order to cause more force or more power seems to be flawed. In Kendo, you must keep your upper body relaxed. Tightening of the muscles (especially seen in beginner kendoka) is almost always the source of error in their swing. Staying relaxed and keeping the shoulders low is key to a proper swing. Again, the cut does not come from landing a hard hit. It comes from a coordinated slicing motion of a blade. Comments?

KFK Figure 3

kfk fig 3, kendo strike

  1. The article states “The shinai hits the target, or men, (the head), at the same time the foot lands, this must be done with power, and accelerates downward with the assistance of gravity at 32.2 feet/second squared.” Again, power in so far as hitting hard is not the objective. A “strong” hit is very different from a “hard” hit. In a strong hit, the body is balanced, the shinai and the foot land together along with Kiai (Ki ken tai no ichi: Spirit, Sword, and Body as One). At the moment of impact, tenouchi is used to stop the weapon. This is the only time there is a purposeful tensing of the muscles in the upper body and most of it is in the hands / wrists / forearms. Alignment of the shinai, arms, shoulders, and wrists occurs briefly to add support and balance. This is often referred to as the “wrist snap” in Kendo. The majority of the force from the Kendoka’s strike is in the forward direction. The vertical motion (downward) of the foot is minimal as described above. Comments?

  1. Gravity will have a very negligible effect on the shinai’s motion in the scenario of a shomen uchi. The Shinai’s mass is supported/manipulated by the kendoka’s muscles during the entire motion which are exceedingly more substantial than the downward component of gravity. Gravity would only apply (substantially) in this scenario if we removed our muscular support and allowed the Shinai to “free fall”. Comments?

  1. The last issue I have is with the line in the conclusion “It the weapon accelerates this effects the timing of a parry, relative to the distance of the attack.” Acceleration implies an increasing / decreasing velocity. When swinging a shinai, we do not swing faster and faster as we move from overhead toward our target. In fact, a methodical attack with constant velocity will land much more effectively. While speed of attack does affect one’s ability to perform parries, the effect is minimal if proper distance is maintained. Comments?

This purpose of this response article is to simply create possible discussion topics, and to promote information sharing and most definitely not to say “what is right or what is wrong”. Through this action all who contribute and/or read these two articles will hopefully gain an understanding of the topic. I encourage any and all comments and responses either through the submission of further articles to EJMAS, or they may be sent to me directly:

Stephen Quinlan
Kingston Kendo Club

1 Study results reproduced in “Kendo: The Definitive Guide”, H. Ozawa, Kodansha International, p. 132, indicates that the downward force produced by the Fumi Komi Ashi during a Shomen strike is (on average) 884 kgw for an experienced male kendoka and 548 kgw for that of an experienced female. Results indicate that this downward component is equal to a magnification of the kendoka’s body weight by 13.1 and 9.36 for men an women respectively.

2 Definition courtesy of wikipedia.

3 Definition courtesy of wikipedia.

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Physical Training Mar 2008