Force = Mass x Acceleration
by Rob Redmond - September 20, 2008
F=MA is probably the most overused physics equation in the Karate community. Karate
instructors use it to explain how to make a punch deliver more damage to a target. Karate
students use it to explain why they are able to punch more powerfully than boxers (note: such
claims are nonsense). F=MA has been bounced around the pool table of karate physics for
years.
Unless you are a physics major, everything you think about force and karate techniques is
probably wrong.
At the end of this article, I will answer the question: Is force useful for describing the impact
of a fist into someone’s face?
In this article, we’re going to start over. We’re not going to get really advanced in our study
of physics, because most of us will get brain freeze when we see how complex the actual
equations are. If there is one thing I have learned from some of my physicist friends:
Advanced physics is rarely any more useful than basic physics in describing simple principles
that do not require high levels of accuracy. Karate punches don’t need to be measured to three
decimal places, so the most basic understanding describes everything we need. You can go
here if you took years of calculus and want to review the concept in more detail. But for our
purposes, F=MA will work fine.
The Equation
The purpose of the F=MA equation is not to explain “force.” The purpose of the equation is to
explain how force, acceleration, and mass all interact with one another. Instead of thinking it
as the equation for force, think of it as the equation that explains how much force is needed to
accelerate something that has mass.
Mass
Mass isn’t your weight, technically. You have mass whether or not you are standing on the
surface of a planet with gravity. We’re not going to be using mass to help us plot space shuttle
trajectories, though. Since Karate is all done on the surface of the Earth and not in the
International Space Station’s weightless environment, for our purposes, mass is equivalent to
weight in the dojo.
It’s actually far more complicated than that, but the complexity isn’t going to fundamentally
change the concepts we were going to cover. For those of you with PhD’s in robotics: Mass.
Acceleration
Acceleration is a change in velocity (link for geeks) over a period of time. You accelerate
your car by changing the speed you are traveling from 60 mph to 75 mph in order to pass
someone on a freeway. Once you are cruising at 75mph constantly, you are no longer
accelerating. Acceleration only exists when velocity is changing. When someone is traveling
at a constant rate, then there is no acceleration.
There is another important thing to know. Acceleration can be negative. When you hit the
brakes in your car, your speed changes downward. Scientists call this negative change in
speed “acceleration”, too. We ordinary people who earned C’s in math class usually refer to
slowing things down as deceleration.
The time component is important. It takes more effort to accelerate something quickly than it
does to accelerate it slowly. You already knew that. Look at the engine in your Honda and
compare it to the engine in a Ferrari. Ferraris don’t just go faster – they get to faster speeds
faster. Higher velocity and higher rates of acceleration require more performance.
For the science geeks: Acceleration..
Force
Force can be measured only because mass and acceleration leave it behind as a remainder.
You cannot see force. You cannot touch it. You know that something speeds up because you
see it moving. You know something has mass because when you bend over and try to pick it
up, you get a hernia. But force? For is the invisible component of the equation left over by the
other two.
Force tells us how much we have to exert energy against an object with mass in order to
accelerate it.
Using Force
I’ll try to write slowly so that we can both get through this without our heads exploding.
When you use the equation for force, you don’t use it to explain how strong your punch will
be when it lands on a target. That’s not what it is for.
Force is properly used to explain how hard it was to get your arm moving, or how hard it was
to slow your arm down to make the punch come to a stop before your elbow blows out.
It’s not an equation that explains impact delivery, damage, or probable results from you
hitting someone else in the jaw.
That’s where most Karate people go wrong in using the equation for force. They talk about
how much force their punches have, and how much force is required to break bones or boards.
But really force isn’t your best pick for trying to figure out board or bone breaking. Force is
best used to figure out what it takes to get your meat hooks moving quickly toward your
opponent.
Force is measured in newtons. A newton is equal to 1 kg x (m/s^2).
Force = mass x acceleration tells us that if our arm weighs 10kg, and we want it to accelerate
from 0m/s to 10m/s in just 1 second, then we end up with 10kg x (10m/s^2). That’s 100
newtons of force it would take to accelerate our arm that quickly.
It’s actually much, much more complicated than that (but of course), and most of we ordinary
people who do not work using the calculus we took our freshman year of high school every
day would become nauseous if we read more about Force, but suffice to say that this level of
understanding will suit our purposes perfectly.
Just don’t build any tall suspension bridges using this information, and you should be fine.
This level of detail is perfect for describing something as variable and individualized as a
karate punch. We just need to understand the concept, not save lives with ten-thousand
degrees of accuracy.
Conclusions
Force tells us how many newtons of push or pull on an object must be exerted to get it to go
faster or slower in a given period of time. Mass tells us how heavy the object we are going to
push or pull on is, thus making it require more or less force to move it. Acceleration is how
much faster or slower the object will move, thus requiring more force or less force depending
on how dramatic of a change we are trying to create.
When you punch with your fist, your muscles exert force on your arm to straighten it out in
front of you. The heavier your arm, the more force is required. The lighter, the less force. The
faster you try to accelerate your arm to a high speed, the more force. The slower and more
gradually you increase the speed, the less force.
When you are about to land your punch, if you start tensing your muscles to tense on impact
or otherwise control the punch, you are applying a force against your arm again – this time in
the opposite direction. Your arm slows down over a period of time. Again, how quickly you
slow your arm down and how heavy it is determines the force needed to slow it down.
None of this tells us anything about the impact. Nothing. Nada. Zippo.
Is force useful for describing the impact of a fist into someone’s face?
If you want someone else’s face to start moving rapidly away from you, then the equation for
force would let you know that if their face weighed 10kg and if you applied 100 newtons of
force, their face would start accelerating away at 10m/s^2, then reach a constant velocity, and
then probably slow down due to all sorts of other forces acting on it.
Here’s where a little common sense helps.
The goal of a karate punch is not to accelerate the opponent’s body parts and set them in
motion. Usually, the desired effect that a fighter tries for when they hit someone is to cause
pain, cause loss of function, or cause loss of consciousness. What you want to do is wind
them, break a bone, knock them down, or knock them out.
When a boxer knocks someone out, yes, it is because they cause their opponent’s head to
accelerate rapidly. The opponent’s head decelerates rapidly because it is attached to shoulders
by a neck. The brain has inertia (it keeps moving), and collides with the inside of the skull
causing trauma, dysfunction, and perhaps permanent damage. So, you could say that
accelerating someone’s head with a padded fist is effective for causing loss of consciousness
in a boxing match. However, the unconsciousness is not caused by the acceleration of the
brain. It is caused by the collision of the brain with the inside of the skull. Force won’t tell us
anything about what happened there. For that, you want to study momentum and impulse.
In a self-defense situation, which is the only time they are really worried about how powerful
their delivery is, a karate player will use his bare knuckles, perhaps even just one knuckle, and
the small surface area means that it is less likely that someone’s entire head will accelerate
and decelerate causing the brain to hit the wall and cause the lights to go out.
What is more likely is that the immediate target area will be damaged and crumple to absorb
the blow. In boxing, people are knocked out. In Karate, they have teeth knocked out, they
have their jaws broken, their cheek bones are broken, their noses are crushed, or their ribs
snap in half violently.
Karate strikes are more likely to cause acute, localized injuries. For these, you could use force
to say that pieces of the body parts were accelerated quickly, and that the acceleration was so
rapid that the rest of the body part couldn’t keep up, stress occurred at the edges of the
accelerated area, and then damage, pain, and ultimately body part failure resulted. But that
doesn’t explain whether the body parts will break, bend, or simply go faster.
Force does not tell us what we want to know about our techniques. Instead, the only real force
we can measure is the force we must exert to make our arm accelerate and decelerate.
So, what have we learned?
The lighter your arm, the less force it takes to accelerate it
The lighter your arm, the more acceleration you can get with the same force
If you tense the wrong muscles, you will get force pulling in the opposite direction,
and this will counteract the force you are using to accelerate
When you start to control a punch or start tensing for the impact, your fist is
decelerating and a counteracting force is exerted away from the target
I think early Karate instructors in the United States found boxing to be their primary
competing sport, and so they drew a lot of comparisons with it – many of them pretty lame. I
think they were trying to show that Karate is superior by saying that a boxing punch can exert
so many newtons of force and a karate punch can exert more. I don’t know how they
measured this. I’ve seen some machines that supposedly measure newtons when hit, and I
have to say, I am dubious.
I am pretty convinced that force is not really what you want to be measuring when you are
trying to determine how ugly it is going to be when your fist or foot lands on someone else’s
body. I think what you want to measure is momentum and impulse. When you choose to
measure momentum and impulse, there are certain ramifications that are pretty powerful. For
example, you don’t need to be touching the ground to transfer momentum. Bullets have
momentum. But that is for a future article.
What can you do with this information?
* Lose weight. If you want to accelerate your arms and legs more quickly, then you need to
maintain the same strength and reduce the mass of your limbs. If you want to accelerate your
body more quickly in a step, drop some extra tonnage and you will be able to increase your
velocity more quickly – assuming you don’t do some stupid crash diet that causes you to lose
muscle and strength while losing the fat.
* Build strength. If you want to accelerate your body more quickly, then increase your
strength so that your muscles can bring more force against your body’s weight.
Is this a magic ratio: Strength to weight? The lighter and stronger you are, the more likely you
will be able to get your body parts moving quickly. This could potentially reduce your
reaction time and increase your ability to place well-timed blows on a target.
Karate Is Still Not A Science
by Rob Redmond - September 11, 2006
The article Karate is Not A Science has generated quite a bit of feedback. Some are not
convinced Karate is not a science, and some are willing to concede it isn’t exactly a science,
but they are still clinging to the idea that somehow there was drive-by science involved in its
development. I wanted to revisit this topic and explain why it is so important that we
understand our Karate is not based in Science but instead in belief.
Some of the readers have commented that while Karate is not developed in a laboratory by
men in white coats looking through microscopes, that it is still created using empirical
methods, and therefore has at least some basis in science. If only that were true. But it isn’t.
This fallacious argument is made, I believe, as a way of somehow lending particular
credibility to a particular style of performing Karate. Sure, I used to buy into this argument
myself when faced with someone doing Tae Kwon Do or some other style. When they asked
me why we did things a particular way, I’d arrogantly pronounce Shotokan a scientifically
researched and designed martial art whereas TKD was the product of Koreans learning
Shotokan for six weeks after being conscripted by the occupying Japanese army. But I was
wrong about that.
Where did I get that idea? From various Karate books, of course, written by Japanese
instructors who loved to write about how Karate was being developed scientifically, and who
published interesting, scientific-looking data in the backs of their books with graphs and
supposed empirical research.
A style of Karate is mostly a connected series of decisions about how to best handle a set of
variables. But an entirely different set of decisions could have been made with equal validity.
This is what makes Karate art instead of science.
Since then, I have come to realize that Karate is not a science, and wasn’t developed
empirically. It is a tradition, a craft, an art. It is mostly a connected series of decisions about
how to best handle a set of variables. But an entirely different set of decisions could have
been made with equal validity. This is what makes Karate art instead of science.
But why can’t we at least say that it was studied and refined using empirical methods?
Various methods of performing Karate techniques were not tested, the various outcomes were
not measured, and the best way of performing a technique was not documented through
evidence and then adopted. In fact, almost exactly the opposite happened.
One method of performing a technique was adopted because the revered instructor ordered it
be adopted, and it was rarely if ever tested against anything resembling a human body, the
evidence for its effectiveness was not documented, and today, various people perform the
punch in significantly different ways using entirely different methodologies within the same
style of Karate – indicating that there is no “best practice,” no documented knowledge of how
to perform one best, and little more than supposition as to what might work.
The problem with Karate techniques is that they do not exist in a vacuum. You can say,
“Punch like this to deliver the most force,” and someone else will say, “No, that method
leaves you vulnerable to attack. Punch this way and get enough force but some protection.”
And yet another person will say, “No, that first way does not produce extra force. It produces
enough to break some boards, but you would be more powerful against a human doing this
instead.”
And yet another will say, “You are all three wrong. Punching like that is for punching the air,
not for punching a person, and trying to develop self-protection while punching is pointless.”
To complicate the issue even further, none of these people have any measurements of how
much force is generated, and no outside way of observing how much force is generated. They
don’t even have the ability to determine whether or not force is what they ought to be using as
a measurement of an effective punch. They cannot even agree that punches should first and
foremost be strong.
That is not science. That is the very definition of an art. I can hit a board and see it break.
Someone can coach me to punch a particular way, and I can break the board more easily. But
your jaw is not a board, and were I to try to punch you in the jaw, the results are not exactly
predicted by the board, and I cannot be sure that I used the best method, even if my attempt to
break your jaw was successful.
Should I be trying to break your jaw at all? I don’t know. Maybe the punch would be more
effective, meaning that it would be more disabling of an attacker, if instead of breaking the
jaw I simply impacted the jaw with less force, causing perhaps more immediate pain and less
chance the attacker would be stunned into numbness.
These sorts of variables and unknowns – these are the hallmarks of something that is not a
science and not developed scientifically. I want to be clear about this, because so many Karate
instructors and famous authors have claimed that Karate was refined using scientific methods.
I think that no science or empirical research at all went into the development of the Karate
product. There is not even a unified Karate product to observe and say “This was our result.”
Karate is absolutely not a science. In fact, I cannot see any signs of science in Karate’s
development at all. Goju and Shotokan practitioners cannot even agree on where the draw
hand goes on the body. They cannot agree on the best method for developing an effective
punch. And Shotokan practitioners do not agree on whether or not using tension at the end of
a technique is effective or debilitating but protecting of joints.
I think that no science or empirical research at all went into the development of the Karate
product. There is not even a unified Karate product to observe and say “This was our result.”
Karate was developed and refined through various people’s differing opinions, speculations,
beliefs, superstitions, misunderstandings, and traditions. It was toyed with repeatedly, but I
don’t think you can call one guy’s experimenting with possibly doing things a little differently
empirical research. If that were empirical, then you would also have to confess that my beliefs
about tension at the end of the technique being counter-productive were developed through
empirical means.
I used nothing but reasoning to come to that conclusion. I did not experiment. I don’t have a
radar gun to punch into to measure the speed of my punches. I was not able to determine what
delivered the most force, and couldn’t even tell you for certain if force is even the right thing
to measure in this case.
Karate is art. Pure and simple. The evidence says it is an art, the product varies from person to
person like an art.
Unless you can tell me how many foot-pounds of pressure, how many joules, or how much
acceleration, or even how much speed you tend to generate, then do not think that any science
is involved. Without data, there is no science, and there is no data.
Think about that. There is no data at all. None. There isn’t even agreement on a goal we
should be gathering data about.
Until you can show a unified best practice, there is no evidence of authentic research and
development. Without any evidence as to what works, people will adopt preferred methods
based on their beliefs rather than evidence. Without evidence, there is no empirical research.
It’s an art, a craft, a sport, a method of exercise, a hand to hand combat method… Karate is a
lot of things, but it is not a science.
Now, to the real question. Why do I care whether or not people say Karate is a science? This
is the really the most important point in this entire discussion. It is because when Karate
practitioners believe that their particular methods are somehow proven out to be conclusively
the “proper way” or “best way” that they begin to develop style bigotry. They begin to think
that Shotokan is better than Goju-Ryu, or that Olympic TKD is foolish nonsense whereas the
World Shoto Cup is where the sun rises.
This sort of style-centric thinking retards our development. We find ourselves preferring our
own methods, eschewing the methods of others, and locking ourselves in a virtual closet,
refusing to listen to reason from anyone else.
But when Karate is art, when we think of it as an art… let me be more aggressive in that
statement… when we realize the truth that Karate is definitely not scientific at all but is art the
same way music is art, we can get together with other people and listen to them instead of
simply impatiently waiting to explain to them why our way works better and how scientific it
is. We become open to the fact that other arts are equally valid for their own reasoning and
approach to the same problem.
SHU/mamo(ru) –
(v.) to protect; to
obey.
HA/yabu(ru) – (v.)
to tear; to rip; to
break.
RI/hana(reru) – (v.)
to separate; to leave.
And this very important, as I wrote about in my article SHU, HA, RI, Karate development is a
maturation process. And that second step, where we begin to express our independence
without yet going so far as to be creative, is when we look over the fence and say, “That kata
Sepai those Goju guys do is pretty cool. Hey, can you show me that?”
Like musicians, we can share our songs with one another. We can learn each other’s methods.
We can get together and expand our understanding, widen our perception of what is valid, and
by opening ourselves to possibilities, we mature, make new and interesting friends, and leave
behind the comfortable dogmatism that protects our egos from things we are afraid of, such as
the fact that our Karate is not any better than anyone else’s.
Making Pressure into the Floor
by Rob Redmond - July 2, 2006
Pressure is the result of two surfaces in contact with one another where they exert force
against each other. If you stand on your feet, your feet with exert force against the floor equal
to the mass of your body in Earth’s gravity. When that force is calculated against the surface
area involved, the amount of pressure, pounds per square inch, can be derived.
Believe it or not, there is a rather large group of people out there who practice Shotokan
Karate who believe that by manipulating their body weight, they can, without pressing
upward against anything, increase the pressure that their feet are making on the floor. They
also believe that they leverage this increase in pressure for their own use in creating stronger
Karate techniques. Maybe they can.
For example, what happens when you jump upward in place? Don’t your feet exert more
force than your body mass as you push off? After all, force is equal to mass times acceleration
(F=MA). When you push off, you accelerate your body weight upward, and therefore increase
the force the feet put into the floor.
Likewise, after you jump up and start to come down, your feet will, temporarily, exert more
force into the floor until the acceleration of the floor is spent and your body is once again at
rest.
So, the question is, can you harness this temporary increase of pressure into the floor in your
Karate techniques in order to give them a little more gusto – and perhaps make them a little
more reliable and likely to put the hurt on someone when you have no other choice?
Not really, no.
Sorry, I just blurted it right out without all of the arguing against it, examples, and other
supporting reasoning, didn’t I? Oh no! I’ve ruined the whole article before I even really
caught your interest!
OK, so here are some examples an supporting reasoning. Read on, because despite my
disagreement with making pressure into the floor, I will make a cause for you to do something
else that will be useful for you.
Example 1. You stand in a front stance and throw a reverse punch. If you bend your knees a
bit, and then straighten them both to lift both feet up equally, you will temporarily increase
the pressure you are exerting into the floor, and then you will start to raise up off of the floor.
If you throw a punch forward at this moment, the force into the floor will go downward, and
your punch will go forward. When the punch lands, nothing will be different. That is because
force doesn’t travel around corners. You cannot make a force that goes down to the floor help
an action that is pushed in front of you. Essentially, you end up pushing outward from your
body’s center in both directions.
In fact, I would argue that this would probably make your punch weaker, since by pushing
down with both feet, you have no opportunity to push forward against the floor with the rear
foot, which actually could make your punch more robust.
Example 2. You are in the air dropping downward in place, and you throw a reverse punch
which lands as your feet do. Let’s be brief: this doesn’t work either – for the same reasons.
Example 3. You are standing in a front stance, and you tense the muscles on the insides of
your legs so that your feet pull toward each other. However, your feet are stuck to the floor, so
the tension builds and your feet don’t move. Does this work like some sort of suction cup to
increase the amount of pressure your feet put into the floor?
Not even a little bit. Basically, all you are accomplishing here is to exercise the insides of
your legs with isometrics. Your feet are still not pushing into the floor with any more force
than your body mass. However, you are pushing against friction, and your legs and feet are
straining. What does this result in?
Your front foot is now easier to sweep, that’s all. Your feet are “pre-stressed” against the
floor, loaded with horizontal force that is testing the limits of the friction that keep them in
place. Add just a little tap to either foot in the direction the legs are pulling, and POP! The
friction is no longer enough to prevent movement and the foot’s grip on the floor is destroyed
and replaced with your back gripping the floor.
In short, you cannot increase your karate techniques’ power by pushing off with both feet
upward, nor by dropping your body weight downward. At least not a horizontal technique.
You could increase the force of a punch directly upward or downward, because these forces
would be complimentary. So, there are some rare instances in which it would work – even if
those situations are extremely unlikely.
And, you cannot increase your karate ability by gripping the floor by squeezing your feet
toward each other. This actually weakens your stance by providing helper force to unseat the
feet.
These three concepts, and the others like them, all have a flaw which doomed them to being
demonstrably false. The flaw is that the mass of the human body is constant, and so is the
force of gravity. While you can push up or come falling down to generate vertical force, this
doesn’t really do anything for you horizontally, and while you can make horizontal internal
stress, this doesn’t turn into downward pressure into the floor.
Force doesn’t turn corners. That’s the problem.
However, force does do another trick which you can take advantage of. Force uses mass as
one of its components, and it can be increased if you can find a way to increase your mass.
Obviously you are not going to succeed in making yourself weigh more without lifting
weights, shooting up steroids, or eating Ben and Jerry’s Ice Cream by the bucketful. But you
can increase the amount of your mass which is involved in any one of your techniques.
You see, most people make the incorrect assumption that by pushing off with the back leg,
stepping forward, turning their hips and shoulders, and punching forward either in place like a
baseball batter or by stepping forward into the motion, they are utilizing all of their body mass
in the technique.
But the truth is that most of your body mass is not behind your punch. When you turn your
hips, any of your body parts not in motion directly behind the fist pushing it forward are not
part of the mass of the technique. If you reverse punch with your right hand, your body’s left
side is, for the most part, completely uninvolved in the technique.
However, there is a way to leverage a lot of that weight. I call it “Unweighting the
Technique.”
You see, when you stand in a front stance, most of your body weight is on your front foot
because your center of gravity is forward. The rear leg has only a portion of that weight. If
you can push into the floor with that front foot and lift some of your weight up, it will be
unsupported and need to fall back to the ground.
If you punch forward as your body weight is falling back down and try to hold your front foot
off the ground with your fist and arm pushing into the target instead of with the front foot, the
mass of the technique is greatly increased.
Force doesn’t go around corners, but it does bend around angles that are less than 90 degrees
just a little within the human body. You can, for instance, push backward with your rear foot
and your fist is supported going forward, even though the rear leg is not directly behind the
fist.
In effect, by unweighting your front foot, which you can do without pushing down but by
simply lifting the foot slightly on impact with any heavy bag, makiwara, or person, you do the
same thing as removing one of the legs from other a table. As the table falls and hits the wall,
it damages it, because the weight of the table was not falling straight down. The table was
falling at an angle. Your body is falling at an angle as well.
This wouldn’t work if you were not in a front stance. It is the angle of the rear leg being
pointed upward and toward the wall that makes it work.
Here is a verification this works:
1. Stand in front of a wall in a front stance and put your fist into it.
2. Push the fist in as hard as you can. Feel the force?
3. Now lift the front foot. Feel the increase in force?
That’s it.
Now try it against a heavy bag. If you are sloppy and new to this, you will lift the foot too
soon, land the punch too late, or lift the foot too much and too obviously. As your skill with
this technique increases, you will find that you can subtly lift the foot only a centimeter when
the punch lands and get a whopper of a bonus force out of it.
That’s just how it works standing still. This is even easier to apply in more advanced
techniques when you step or shift. Simply land the punch before the front foot settles with all
of the body’s weight on it, and you’ll get the extra mass behind the technique. You will
essentially be catching your body on your fist for an instant.
You may find when you do this that your fist and wrist take more of a beating using a heavy
bag or makiwara. You might want to start off a little slow and see what happens. Many people
have reported to me that after they incorporate this habit into their techniques that it makes
hitting things much more painful and difficult. They also report it makes doing things like
kata much different.
I will be the first to admit that karate punches are not likely to drop anyone unconscious in
one shot. This extra zip to your technique might not help anything at all in the real world. It
might just be something new to play and experiment with. But, give it a try, and see what you
think. And remember, go slow, and don’t come crying to me if you do what I did and tear a
muscle in your shoulder experimenting with this.
Dr. Hui has written a great article about this concept which can be found on this site here:
Unweighted Vectors: Forces in a Strike
The Physics of Effective Techniques
by Alexander Hallock - April 12, 2006
A dairy farmer, concerned about the efficiency of his operation, hires a prominent scientist to
observe and hopefully make corrections. The scientist follows him around for days watching
the cows come in and out, eat, sleep, and do whatever it is that cows like to do. The farmer,
finally, asks the scientist to construct a model and to tell him how to get maximum results for
minimum inputs. The scientist begins to construct his model: assume all cows are perfect,
hollow spheres filled with uniform milkIt’s an old story (among physicists) but a good one that illustrates an important point. Good
physical measurements tend to come from extremely reductionist models. You have to be
careful, though, about applying the results of a simple analysis to what is a stunningly
complex problem. Take global warming, for example. One can accurately measure the level
of water in the ocean around the world. If you look in the right place, it slowly rises over the
last 50 years. Now comes the hard part: what does that mean? Surely one measure on one part
of the ocean over a small amount of time isn-t a complex enough gauge to really map and
understand Earth-s climate. It isn-t completely useless, either. I consider it more of a -look
closer- and -think deeper- statement about climate, not a statement about impending doom. I
can use Newtonian mechanics to help you understand Karate, but you-ll need a healthy dose
of common sense to understand how to interpret what I measure.
I. How fast can I punch?
Here-s the simple measurement. I filmed myself doing a series of straight punches in front of
a background that had distances clearly marked on it. I could then go frame by frame (I knew
the frame speed) and note the distance my fist had traveled. This let me crudely map velocity.
Today, anyone could do this in an afternoon with a digital camera and a computer. Consider a
simple reverse punch from a zenkutsu dachi. What you see is quite intriguing: the fist
accelerates out of the chamber rapidly, then slows down, coasts for a bit, then accelerates
again and finally slows until it stops. The first peak tended to come at around 15% extension
and be about 80% as tall as the maximum which happened around 75 or 80% extension. I
assume this is a result of biomechanics. Something about the way in which our muscles work
to extend the arm isn-t constant across the whole extension. So I should be making contact
with uke around 75% extension. It’s a little closer than I was used to, but not a huge
adjustment (phew).
There is some actual, physical truth to the idea of going through boards but locking down
when you hit people, at least for soft targets.
The velocity itself came in just under 10 m/s for the best punches I could do. It didn’t seem to
change much with different stances unless I was unbalanced. So the lunge punch was as fast
as the reverse punch. I-ve heard many people tell me the reverse punch is more powerful, but
the lunge punch is faster. Not that I can see- The lunch punch tended to be weaker (for me)
because I couldn’t put as much weight behind it. They were both the same speed.
II. How hard can I hit? Translation: How much kinetic energy can I generate?
Here-s where the physics get dicey. Everyone wants to plug into ??mv2. OK, fair enough, but
what do I use for m? I-ve seen many people just plug in their weight which is silly. That-s the
force you-d generate if you were shot from a cannon. The way you have to do this is to break
up the entire arm into little segments. Each has a small mass and some velocity profile. I then
have to map out what each piece does and sum them all up (integrate). This is just too
cumbersome, so I-ll settle for trying to calculate an effective mass. What I can do is use
something that measures the force of the punch while measuring the velocity and work
backwards to see what my effective mass is. Picture punching a bathroom scale (something Ive done). It isn-t quite that simple, which I-ll go into later, but you can back out a number
which is quite surprising: just under 3kg. That-s probably the weight of a decent fraction of
my arm. What-s up? Should I be able to throw some huge fraction of my weight behind my
punch by twisting my hips and pushing off the ground? No, not really, no. If I want to get this
number up, I have to be moving. Then again, if I-m moving, I can’t use a solid, stable stance
to help me get my velocity up. I-d love to measure v for a punch while I-m stepping forward
into zenkutsu. I have a feeling this is what -unweighting the front foot- is doing. It is allowing
you to slide forward a bit so your effective mass is bigger.
Working with what I have, for the moment, means I-m generating ?? (3 kg) (10 m/s)2 = 150 J
(Joules). This is the amount of energy it would take to lift 150 kg 1 m – so what it would take
to deadlift 330 pounds. Not insignificant, but then again your heart takes around a Joule per
beat. The problem with this type of reasoning is that you really want to calculate the force of
the impact and to solve that we-ll have to know something about the time in which this
collision takes place.
III. How hard can I hit? Translation: How much force am I generating?
Try the following experiment. Fall from a nice osotogari onto some cushy mats. Now take the
same fall in the parking lot. Notice a difference? You hit the ground with the same amount of
kinetic energy in both cases. The problem lies within the nature of the things which are
colliding. I need more details about the collision. The object I hit is going to have some
amount of flex and so the collision time is going to change. Due to the nature of my target,
some of the energy will go into destroying the object, and some of it will go into wasteful
things like heat. The way force changes with time (rather humorously called yank) matters,
too. Certain plastics, for example, can hold up under enormous pressures if you ramp up the
pressure slowly. If you do it quickly, though, they rupture at relatively low values.
All these properties are measured extensively for bulk materials. I-ve never seen them for
humans, unfortunately. Wood has a lot more flex to it than brick. If you look up thinks like
compression strength, impact strength, Young-s modulus, etc. for wood and for brick you-ll
find something interesting. Wood is much tougher to break. Bricks are harder to break
because of their dimensions. If you had a block of pine that was the same dimensions as a
brick, the wood would be more than 10x harder to break (with the grain, and even harder
against it). Clearly, how the target responds is important.
Suppose I hit someone square in the chest and my fist sinks in 2 cm. I-ve it them at the proper
extension and so on so I-m giving it my full 300 J. Now I can estimate a force. I-m going
from 10 m/s down to 0 m/s over a distance of 0.02 m with a mass of 3 kg. You could also
think of it as 300 J with a stopping distance of 0.02 m which gives you 15,000 N (Newtons).
Now we are getting somewhere. I know from past reading that boxers who were punching
heavy bags were registering 2,000 – 4,000 N. Should I go on the boxing circuit? No, probably
not. Don-t let those numbers deceive you. If I punched a heavy bag my fist would penetrate a
lot further and the collision time would be a lot longer. If I make some guesses, I-ll get
something like 3,000 N if my setup was more like theirs so I-m in the right ballpark. Also,
when you punch someone they tend to move. So as I hit, some of my force will go into
pushing them away and not destroying their bodies. Again, you have to guess a lot and do
some tedious algebra, but I figure a good punch puts a few thousand N into the other guy.
The real question you want to answer isn-t -How hard can I hit-? but -How can I get the other
guy to absorb the most amount of force-?.
Here-s where the physics can get really interesting. Suppose I-m punching a softer, squishier
target – something more like my gut than my skull. If I let my fist just plow into it until it
stops, then I have some stopping distance/time. If I tensed up, the -lock down- as in a crisp
Shotokan technique, I can shorten the time/lower the stopping distance. This comes with a
price, though; as I have to pull back on the fist in order to do it. Still, there is a definite region
where you-d win out. A 200 J punch which has to sink in an inch transfers less force than a
100 J punch which sinks in only a quarter of an inch. This concept isn-t a total wash. There
certainly is something to it. To really make it work, though, you have to hit first, then bring
your fist to an immediate halt. It isn-t impossible, but the window is pretty small so you-d
have to be an expert. If you can tighten up before a body backs up or bends away from you,
this ought to help. If you are going to hit something with no or negligible flex, then your best
bet is not to hold back. So there is some actual, physical truth to the idea of going through
boards but locking down when you hit people, at least for soft targets. I hope that I have
convinced you that the real question you want to answer isn-t -How hard can I hit-? but -How
can I get the other guy to absorb the most amount of force-?.
IV. It only takes 6 pounds of force to break a collar bone!
I-ve heard this so many times, and (aside from the unit problem – pounds is not strictly a unit
of force; in fact there was an act of congress declaring the pound a mass as opposed to its
original definition as a weight) it is probably true. It comes out to around 25 N. Decent
punches are putting in thousands of N, so no problem there. If you look at what it takes to
break an arm or a leg, though, you just can’t do it. A human shin can take about 150 MPa
(megapascals) before it snaps. Given an assumption about the surface area of the ball of your
foot, a mae geri would have to generate around one and a half million N to do it. Human
bones are an engineering masterpiece. The lesson here? Break collarbones and ribs.
V. 10 m/s, is that fast?
I can throw a punch that is around 10 m/s which is 22ish mph. It doesn’t sound all that fast
until you realize that the average reaction time is something like ?? of a second. In that time,
my fist can easily go from chamber to your head. I think the reason we are able to block this is
because 1) we all telegraph our moves with posture, attitude, etc. to some extent and 2) we
only try to hit certain targets which means the defender-s brain doesn’t have to try and cover
the whole body. I tested this out at one point – try the following during sparring. Twitch your
right hand, step in with a left zenkutsu giving the impression you are going to throw a right
punch. Instead, throw a left one to uke-s right thigh. Not as common a target, but you-ll nail it
nice and hard without much trouble. This highlights a problem with karate training: we tend
to practice sparring with people who do the same art as we do so we can more easily read
what they are going to try.
Conclusions
1) Hitting a human being is tremendously difficult to model accurately. There could easily be
some important factor I-ve missed. Think about what I-ve said and, most importantly, do your
own experimenting.
2) More punching power will come from being able to put more weight behind your punches.
Olympic boxers showed punch strengths that correlated strongly with weight so bigger is
better. On the other hand, the heavyweights outpunched the lightweights by around 30%. You
are probably best off working on targeting because even a weak punch can destroy collar
bones, ribs, and the windpipe.
3) Kime or -locking down- of techniques isn-t 100% b.s. It seems to me that it could help with
soft targets, while hard targets demand you just barrel into them. I suspect, though, that
physiology matters a great deal here. You have to worry about biological considerations like
hyperextending your elbow which I haven’t considered at all. Be skeptical, but don’t discard
it yet.
4) Punch speed versus reaction time tells you, clearly, that you should be the aggressor. The
idea that there should be no -first attack- definitely is b.s. Practice what it is like to block
someone coming in with something nonstandard. I have found that techniques which are
outside the normal repertoire are super-tough to block.
Copyright © 2006 by Alexander Hallock, PhD.
Dr. Hallock is a chemical physicist who has studied martial arts for 11 years.
Karate Is Not a Science
by Rob Redmond - February 8, 2006
It doesn’t require a lot of searching through Karate books or Internet sites to find a statement
that Karate is both art and science, or that Karate is scientific. No matter what style of Karate
any of us may study, one thing is very clear to me: There is absolutely nothing scientific about
Karate. In fact, I will even go so far as to say that calling Karate a science is like saying the
Earth is flat. Normally I would soften my opinion with a phrase like “I believe,” or “I feel,”
but I don’t think that is appropriate here. Karate is not a science. In fact, Karate is almost a
perfect example of everything that a science is not.
A science is a collected body of knowledge which has been gathered and tested using the
scientific method. The method is relatively simple to describe. A scientist wonders whether or
not something is true. He proposes a hypothesis, which is a statement of speculation, and he
sets up a test to determine if the evidence shows it to be true or not. He then publishes the
results of his test as well as the methods that he used to obtain his results.
The published study is then critiqued by his peers in his field of scientific endeavor. They
point out any flaws in the way that the test was performed, the analysis was completed, or the
results were tabulated. They will also try to perform their own tests using the same methods to
see if they get the same results. Other scientists will also perform modified tests to check for
flaws and errors in the original study.
While Karate might be argued to be a body of knowledge, it certainly was not created using
anything approaching scientific methods.
This process is relatively simple to describe at a high level, but extremely tedious to actually
engage in. It requires a very analytical and detached mindset, a willingness to go to extreme
depth of detail in describing and defending an idea, and a recognition that the peer review
process allows the body of knowledge to be increased in a slow, careful, and cautious manner
so that misinformation and passionately held but incorrect beliefs are not allowed to be
adopted.
While Karate might be argued to be a body of knowledge, it certainly was not created using
anything approaching scientific methods. The technical methods were conceived of by
individuals who merely preferred them, modified based on personal beliefs, and the body of
knowledge is kept not by those interested in peer review, but by people who hold it as
tradition that the knowledge and those that have it shall not be questioned or challenged by
their peers.
In fact, I would even argue that Karate is not a body of knowledge, but rather it is a body of
opinion. After all, I know of no one who has taken a group of people, divided the group in
half at random, trained one half in boxing, another group in Karate, and then used objective
criteria to test the training and performance methods against each other for effectiveness.
Such a study is typical in a scientific endeavor. In Karate, it is unthinkable and no such thing
has ever been undertaken.
The few studies that have been performed on Karate are, well, there is no tactful way to say it.
They are entertaining, but from the perspective of a professional researcher, they are quite
pathetic. Tiny groups of people who are advocates for Karate are compared to one another
without any accounting for physiological or other individual differences. No random or
evenly skewed control groups are ever used. And, most importantly, studies performed seem
not be real science, where an idea is truly being questioned. Instead, justifications for dearly
held beliefs are sought by those performing the studies.
That is not science. That is rationalization. It is excuse-making for the traditions of Karate.
Were Karate a scientific endeavor, we would seek to discover whether or not punching from
the waist with a turning motion was actually superior to simply punching from a boxing guard
for generating a devastating impact. We could test this by taking hundreds of Karate experts
within a certain physiological range and compare them to a similar sized group of boxers with
similar experience and physiological characteristics. We could then have them punch into a
device which would measure some output from their techniques, whether it is force, impulse,
momentum transfer, or whatever.
Such a study would be fascinating. We could then take those results and say, “People on
average punch more powerfully using method A by a margin of X.” The margin would tell us
if there was a significant difference between the training methods in terms of results in the
real world. Others could read our study, criticize it, and suggest improvements, and we could
try it again. Our friends could put together their own studies and see if they come up with the
same results.
No crucible for Karate ideas was formed upon which ideas were either shown strong and
resilient to challenge or fragile and impossible to defend.
Karate would definitely be a science if, after finding out that a different method of punching
was superior through repeated and careful testing, we stopped using our old method, and
adopted the one that science had shown us provided more benefit at lower cost. But let’s be
realistic. No one in the Karate community is going to stop doing his Karate techniques the
way he prefers, even if such a study were made available.
That is one of many reasons that Karate is not a science.
Karate was not developed using experiments to determine the best methods. No crucible was
formed upon which ideas were either shown strong and resilient to challenge or fragile and
impossible to defend. Karate was invented from whole cloth, one step at a time, one person at
a time, and the supposed science used to examine it was done after the fact as a way of
justifying various concepts such as belt ranks being indicative of skill or punching from the
waist generating useful force.
Karate was invented and then justified, not experimented with and then invented.
Some might point out that something akin to the scientific method was used over generations
as the Chinese and later the Okinawans adopted ideas over time via their own personal
experience and private experiments during hand to hand combat. I don’t believe that is a very
good example of scientific research for a number of reasons.
Even if I am willing to ignore the fact that in those Asian cultures where Karate was born the
elderly wise men who were considered masters of the art were never questioned or challenged
by their students and rarely did anything resembling real hand to hand combat, I cannot ignore
that private, personal experience only works for the person doing it.
My experience may not translate out to other people. And even if it did, we would need to test
that and challenge that idea. If you are curious as to how popular it is in any Shotokan Karate
dojo to challenge commonly held ideas, just announce to everyone that you read this web site
regularly and agree with most of what is written here. You will receive your confirmation that
dissent is not entirely welcome in short order, I assure you.
Consider all of the untested assumptions in Karate practice that are based merely on tradition
and have nothing to do with scientific research. The kata are purely a tradition, and no
evidence exists that they are even a healthy exercise much less effective for developing
mental or physical skills in fighting. We’d like to believe its true, but show me the tested
evidence, the studies, the methods use, and the results. Show me the large, random samples of
Karate experts tested against control groups who did other exercises or martial arts and let’s
see if Karate’s kata really hold up as a comparably good exercise and developer of body and
mind. Maybe they are too anaerobic to be really healthy for exercise and lacking in resistance
for the building of strength. Maybe they only help mental acuity as an exercise while you are
learning new ones, and repeating old ones just allows the mind to shut down and stagnate as if
watching TV. There are a ton of possibilities, and the benefits of kata are just one of hundreds
of possible scientific studies that could be performed to test the value of various aspects of
Karate training.
Saying “Karate is a science” makes it sound as though our methods were developed in a
laboratory and all other systems of Karate must acknowledge that we have been proven to do
things better.
Would we acknowledge these results if they were put before us? How many Karate experts
are willing to consider a different opinion from theirs in a speculative article about tensing
muscles on impact? When I consider the number of people who read the article about the
myth of focus on this web site, and how few actually agreed with it and thought, “That makes
perfect sense. I should modify my practice,” I chuckle with the knowledge, the firm,
unshakable knowledge, that Karate is no science.
It is a system of faith, belief, tradition, and custom. It is perhaps best described as a craft.
The idea that Karate is a science is trotted out every now and then by someone who is very
passionate about their personal hobby and wants other people to feel passionate about it as
well. It is a very complimentary thing to say about Karate practice – that it is scientific. It
makes it sound as though our methods were developed in a laboratory and all other systems of
Karate must acknowledge that we have been proven to do things better.
But the reality is that when someone says Karate and science in a sentence without saying the
words “is not,” that person is wrong. That doesn’t mean that something is wrong with your
Karate practice. The only thing I take away from it is that I must acknowledge and recognize
that the beliefs I have about what makes up good Karate are just that: beliefs. The strongest
evidence I can get my hands on for any particular practice is either my personal experience or
logical reasoning. No physical, tested, objective evidence exists.
That’s why, when you read my site, you are reading editorial after editorial. Just about
anything written on Karate is necessarily little more than an editorial. The only “facts” that
exist on the topic are perhaps the recent history of the art, to a small extent anyway, and the
names of various practices we engage in. How they work and whether or not they work well
is little more than speculation supported by reasoning which may or may not be logical.
Everything else we do is up for grabs – merely our rational, or irrational, beliefs.
Unweighted Vectors: Forces in a Strike
by Ed Hui - January 13, 2006
In a memorable moment in Enter The Dragon, Bruce Lee avenges the death of his sister by
killing the villain O-Hara who is prostrate and helpless on the ground by jumping up and
stamping on him. Bruce-s anguished face is shown in slow motion close-up.
The stamp from a height is possibly the most powerful technique in all of unarmed martial art,
because it combines a strike by the most powerful limb of the body, moving in the direction
of the strike, with the entire weight of the body, against an opponent that has the immovable
support of the earth behind him.
When we watch such a thing, even when exaggerated for theatrical effect, we have no
problems with intuitively understanding the way these separate contributions each add to the
destructive power of the strike. But there has been much controversy as to how to understand
the theoretical way in which these contributions add to any technique.
Just as an example, many commentators have suggested that kinetic energy (KE) is a useful
measure of the power of a punch, because KE= 1/2 mv^2, so if you know the mass of the
striking object and the speed it’s moving, you know what the energy of the strike is. You can
then prove that the faster you move your striking limb, the more energy you put into it, so
more energy is put into the impact.
This is true, but it doesn’t translate well to other contributions. So if someone says that
unweighting the front leg is a good idea, it doesn’t make sense from a KE point of view
because unweighting the front leg doesn’t add speed to the strike. Yet experimenting with a
makawara or by leaning against a wall gives strong evidence that unweighting the front leg is
a good idea. And then there-s the weight issue- how does a vertical force of gravity add to the
impact for a horizontal punch?
So I asked myself, what is the best way of looking at the physics of karate strikes that would
best accommodate all the contributions? I have one advantage in this over many readers- I-m
not a karate expert. I naturally think more from the point of view of the target than the striker.
So I asked myself what is the best measure of the effectiveness of a strike?
A target is damaged when a body part has been distorted beyond its functional limits. It
doesn’t matter whether this is done quickly or slowly. It matters only that the limits of elastic
recovery have been exceeded.
I think the answer is force. (I-m assuming the reader has an understanding of the physical
definition of force- nothing complex, just that they know the difference between force and
energy, and the difference between weight and mass.) A target is damaged when a body part
has been distorted beyond its functional limits. It doesn’t matter whether this is done quickly
or slowly. It matters only that the limits of elastic recovery have been exceeded. Something
like a bone needs a large force to bend it so far that it-ll break, but it needs only to be bent a
short distance. Something like a spleen doesn’t need much force, but it does need to be
distorted a long way. An incoming blow will encounter soft and hard parts, and the timing of
the various contributions to the blow will result in a force profile- a graph where the force
being exerted will rise to one or more peaks and then fall to zero. If the peak arises at a
moment where the resisting tissues are unable to elastically resist, damage occurs.
Other measures don’t have this directness. For example, if you consider kinetic energy, all
you know is that the energy is dissipated on impact. You don’t know if this is into heat, or
movement of the target, or noise.
Looking at force, I immediately realised that everything we discuss can be considered
usefully in terms of force, and at the same time we know from physics that there is only two
things that can change with force- direction and magnitude. As long as different forces act in
the same direction, they can be added without fear of contradiction.
I believe that there are exactly three ways that we can contribute to a strike:
1. By speed of strike. The striking object exerts a force when it is decelerated at
impact by the target. You can use F=MA to calculate it. You maximise this by
accelerating the striking limb prior to impact, and by moving as much of your body
(mass) as possible in the strike.
2. By active work of the muscles. In a punch, you can be actively straightening your
arm after impact, or your back leg can still be pushing. You maximise this by a feeling
of pushing through the impact, and by visualising the impact taking place before the
maximum range of your strike. This is entirely independent of your mass or weight.
3. By geometrical relationship with gravity. You can maximise this by either
striking downwards, or by leaning into the strike. This contribution to a strike cannot
be utilised in space. It depends on the presence of gravity.
Some interesting observations follow from these definitions. 1 and 2 are clearly related. Both
are the products of physical effort by the muscles. The difference is primarily before and after
impact, in that before impact there is little resistance to muscular effort, and the result of this
effort is the acceleration of the striking limb over time, while after impact there is massive
resistance (in the form of the target) and so the effort is directly transmitted as a short term
pushing force into the target. The effect of stance is much greater on 2 than on 1, because you
can generate striking speed in any stance, but you can only push on impact if you have a solid
frictional contact with the floor and a body configuration that can resist the reaction to the
push.
Let-s have a look at how this sheds light on the front foot unweighting issue:
There are two reasons there is a controversy as to whether the front foot should be unweighted
for the straight punch. One is that the unweighting is a motionless state of the limbs and not a
movement in the direction of the punch, and secondly gravity, the cause of the weight in the
first place, operates at right angles to the direction of the punch.
The proof of the contribution of unweighting starts with this force diagram:
The interesting thing is that the magnitudes of the forces and their directions can be drawn as
a rectangle. The shape of that rectangle is defined by the distance between the fist and the
floor as one side, and the horizontal distance between the centre of gravity and the back foot.
The weight due to gravity is constant, and this equals the vertical support from the back foot.
(Nothing else is supporting the figure, because the front foot is off the ground, and the force
on the wall is horizontal.) This means that there is a surprising result- the magnitude of the
push on the wall is entirely determined by how far back the support is in comparison to the
centre of gravity. If you put your front foot down and the support is directly below the centre
of gravity, the push is ZERO. You can confirm this by standing with your toes of both feet up
against the wall and attempt to push the wall. You can’t do it.
The longer the stance, the more push against the wall. This push is independent of the speed
of the punch, and operates throughout the impact phase. The limit to the amount of push you
can achieve is determined by the friction with the floor. If you-re on ice, you just fall flat on
your face, as anyone who-s tried pushing a car in winter will attest. The friction is
proportional to your weight, and since that doesn’t change in a static situation, there is a limit
to the length of your stance before your back foot starts to slide backwards.
The only way to increase this is to increase your weight, which you can do momentarily by
bouncing up and down; you are weightless when you are off the ground and increase your
(apparent) weight when you are at the bottom of your bounce. That-s why people bounce in
competition- to give themselves opportunity for greater thrust. Since both opponents know
this, there is a tendency to synchronise bouncing when out of range. Then it’s a game of cat
and mouse- when someone wants to disrupt the rhythm first. All this depends on gravitynone of it will work in a space station in zero G.
I believe that looking at forces has further explanatory value, for example in understanding
the difference between -strike- and -push- as points on a continuum
So, the fact that it can contribute even when the limbs are motionless is not a problem- forces
don’t require motion to exist. Even now you are exerting a downward force on a chair.
Gravity can cause you to have a horizontal force on something, because if you lean on
something you are exerting a horizontal force on it because gravity is attempting to bring you
closer to earth but your supporting foot is preventing this by friction on the floor. And this
horizontal force contributes to the effect of your strike’s impact because ANY force in the
direction of the punch adds to all the other forces in that direction.
I believe that looking at forces has further explanatory value, for example in understanding
the difference between -strike- and -push- as points on a continuum; the difference being in
the force profile over the time of impact. A strike is a sudden spike of force, while a push is a
longer, smoother curve. Each contribution to the force profile- the speed of the strike, the
post-impact push, the front foot unweighting, contribute to the total force profile. If you get
your timing right, you synchronise the greatest force with the moment where the target
requires the greatest force in order to be damaged. This contributes to the understanding of
why we work so hard on timing. We-re told always to finish techniques together- so the front
foot lands when our punch reaches full extension. This implies that if we actually hit
something before full extension, the front foot hasn-t arrived- it is unweighted. Just so clever
to incorporate all of the above into a simple command in kihon- the techniques -arrive
together.I hope you find this way of thinking useful too. Please bear in mind that I am not saying that
it’s wrong to use other measures, such as energy. You use the properties that have the best
explanatory value for whatever is puzzling you at the time; this post is mainly concerned with
differentiating between three contributions to the strike, and finding a way of looking at them
at the same time.
Kime: The Myth of Focus
by Rob Redmond - December 1, 2005
One of the more outstanding things that anyone observing a typical Shotokan performer will
notice is the particular way in which body dynamics are employed. Most people who practice
Shotokan Karate try their best to move fluidly throughout their motions, and then suddenly
tense not only their extending limbs, but also other parts of their bodies as well. Some
enthusiasts even go so far as to choke their breathing so as to create internal isometric tension
to help with the timing of muscle tensing so that all of the contractions take place at the same
time. This practice is referred to by many as -kime- using Japanese terminology. In English,
the common jargon used is the word -focus.I think it is important to note, here, up front, that I will use the terms focus and kime
interchangeably to refer to tensing muscles on impact. There are other meanings for focus and
for -kime… Notable among these, and wisely prescribed for karate training, are strong mental
concentration, putting conviction into your techniques so that you follow through completely
and with full confidence and effort, and forging technical skills that allow your techniques to
be fight-ending single strikes that drop opponents with only one blow (hopefully).
Those other concepts which can be attached to these words often become red herrings when
trying to discuss the practice of tensing muscles on impact. So when I use them in this article,
I will be referring only to that physical practice.
So, what is the Shotokan expert doing when he makes those snappy actions that are so
precise? And how does he learn to do that? When I was coming up through the ranks, it was
explained to me thus:
-Make yourself like water and ice. Water during movement, ice at the moment of impact. Try
to be as fluid as possible in your movements, for maximum relaxation of all of your muscles.
When you are relaxed, you can move fast. Then, when you reach the point where impact
would occur, tense all of your muscles at the same time, making your body into a single,
linked solid object. Try to achieve as large of a difference between your relaxed state and your
tensed state as possible, so that the execution of your techniques is very dynamic. When
relaxing, relax quickly and to a very relaxed point. When tensing, tense instantly and totally
with all of your effort.-
The punch accelerates most at the beginning, and then acceleration decreases.
Before the arm is fully extended, the punch begins to decelerate.
Impact carries the most force if the impact happens before the
line turns blue.
That is the advice I received and heard repeated by many a famous, and not-so-famous,
instructor during the course of my years of training. I followed this advice religiously. There
were many particular practices I undertook in order to facilitate more dynamic relaxation and
tension in my techniques and body movements. I would hit a makiwara 200 times on each
side daily with reverse punches, enjoying the kinesthetic feel that I was improving the range
between my relaxed and tense states while becoming a stronger puncher. I used to stand in
place and extend a technique, and practice repeatedly tensing and relaxing my limbs, trying to
learn not only to tense tightly and quickly with all of my muscles synchronized, but also to
relax quickly and deeply. Tensing was always easier than relaxing. Through these and many
other exercises, I worked diligently to become a master of focus – someone who, when he
performed, would clearly be seen to move quickly and have his techniques appear to hit
invisible brick walls when they were stopped.
I believed strongly in the value of the practice, my exercises, and the skills of those around me
who could do it better than I could. I confidently believed that the better I was able to focus,
the more damage I would do when I was forced to hit someone to defend myself.
During my training, I found many proposed theories as to why this practice was so effective
that I clung to mercilessly.
One of the theories behind this practice was that it was physics in action. That impact damage
is essentially a result of a combination of speed and weight, and that relaxing helped the
speed, and then tensing on impact linked body parts to give the entire body-s weight to the
strike. Essentially, focusing was an attempt to reap the benefits of speed and weight and
combine them. It was an attempt to cheat at physics and get the best of both worlds – a fast
and heavy object can do a great deal of damage when it collides with something. The faster
the better. The heavier the better. Both? Much better!
Another theory I was given was more complicated. That as the technique was stopped
suddenly, and the body connected, that any stray reaction forces would be expended into the
target instead of being conserved, and they would emit from my now motionless fist and
cause internal damage to my opponent as if I was shooting energy out of my knuckles.
Because of theories like this, I believed that focus, kime, tensing on impact, whatever you
wish to call it, was the definitive difference between Shotokan and other types of karate – the
thing that set it apart. I even considered it something that made Shotokan a superior method to
other methods.
But, some time passed, and I had some thoughts that caused me to begin to doubt. And while
at first I was stubbornly resistant to these doubts and bitterly argued in favor of my beloved
skill at focusing, it was too late. The foundation had cracked, and one reasonable day I found
myself unable to go on lying to myself. I no longer believed that tensing muscles on impact
actually works.
Velocity increases dramatically, starts to level off, and then
drops back to zero at the end of the punch.
Force against the target is maximized if the impact happens
before velocity begins to deteriorate.
My doubt began one day while demonstrating breaking some boards. The entire event was
mostly a joke, intended to make myself and a friend laugh more than actually accomplish
anything. I am no proponent of attacking innocent squares of pine. It rather bothers me
because trees die so slowly after being cut, I wonder if it isn-t like punching a wounded man
right where it hurts. But, all silliness aside, I was punching through boards.
I had trouble getting through a particular number of them held up in front of me. I could not
figure out why I was leaving knuckle prints in them and hurting myself, but the boards were
not cracking in half. My friend, not being any sort of martial arts enthusiast at all, spoke up
and pointed out -Maybe you should just punch all the way through them and stop that thing
you are doing.-What thing-?
-That thing where you tense up right when you are starting to hit it. That can’t be helping.
Why are you doing that-?
I then went into my focus diatribe and ranted appropriately with self-righteous indignation. I
explained the combination of mass and acceleration by linking the body at the last instant of
impact.
But, he used to teach physics. He said, -Wow. If you can do that, you-ll probably go backward
in time, because you would have to tense faster than light if you wanted to do that.At his urging, I hit the boards without any focus at all. Snap! They broke more easily. I tried
some that I had not previously battered. Snap! They were shattered as well.
Uh oh.
Apparently I was doing more damage by just relaxing all the way through the impact and not
trying to tense my muscles on impact at all. This could not be! Unacceptable! Outrageous!
Inescapable.
My friend and I had a long talk about this concept. He watched me move slowly, his mind the
empty cup, unfettered by any agenda or egotistical need to have the results come out a certain
way. He tried to explain to me why focus doesn’t work, and I listened, and now I believe I can
explain it myself.
The unfortunate truth, which I wish were not the case given my significant investment in
learning to tense on impact, is that it weakens a punch, it does not strengthen it.
Contact with the target is most effective if the punch is not
decelerating and has maximum velocity. Do not tense antagonists
to brake the punching motion until the impact is complete or the arm
is in danger of hyperextension – whichever comes first.
When the punch is moving toward the target, it has a certain speed. That speed decreases,
unfortunately, at a pretty slow rate even when a karate master is tensing his muscles as fast as
he can. So, as you begin to tense, you begin to slow down.
But my combined body parts, linked by the increased muscle tension, cause my weight (mass)
to increase! No, this is not so, either. The mass of a strike is the combined weight of the
moving parts that will rest some of their momentum on the striking surface. In a real-world
example, if I throw a reverse punch, the striking surface is the knuckle. The mass calculated
into the force will be all of the body mass that will lean on that knuckle when it hits.
Simply put, everything moving forward at the moment of impact counts, tense or not, as long
as some of its weight is thrown forward to rest on the knuckles for a moment.
Tensing your muscles at the moment of impact slows you down while doing nothing for your
weight. Essentially, this practice not only is not helpful, it is actually detrimental to any
attempt to damage something with your hands or feet. With this realization, that I was, all the
time, not practicing to enhance my technical skill and the lethality of my abilities, I was in
fact learning to intentionally dampen the force of my strikes, I was rightfully horrified.
I did not bother trying to reach out for explanations involving squirting -ki like water- out of
my knuckles nor waves of energy mysteriously radiating forward from my fist after it had
stopped moving. My belief in tensing the muscles on impact was shattered.
Punching a rib or other bone with the intent to break it requires
applying force to a small area and creating high pressure for as long
of a time as possible. This applied force bends the bone, stressing it
until it gives and breaks. The farther you push in, the more stress.
Tensing on impact reduces this effect and causes less bend.
I experimented, trying in vain to reestablish some way that focus might work for me. I hit my
makiwara and tensed on impact. A nice solid hit. I held the makiwara bent backward a little,
and then released it. I then tried punching it without tensing, just punching through it. The
makiwara moved much farther backward, and I could not hold it forward. And let me tell you,
this punch hurt like a- like something very painful and unprintable.
At first, I was thrilled with this result. My tensed punch was more powerful, because it hurt
less and was a more solid hit. I asked a student to observe without telling him what I was
doing. He saw the makiwara go back much further when I relaxed.
I realized that the reason it hurt more was that there was more force involved when I was
relaxed on impact. My knuckles were aching because the reaction force from the makiwara
was equal and opposite, as all reactions are, and the harder I hit it, the harder it hit back. I was
hitting it harder.
And then there was the fact that I could not hold the makiwara back. Why was this true? I
came to realize that the makiwara, the harder it was hit, the more it moved, the more it
resisted. I no longer was pushing it back only as far as I could resist it without the added force
of moving. It was now pushing back so hard that the reaction was too strong to hold forward
while standing still.
Punching into the abdomen or another soft tissue area not protected by
surface bone is the same. The farther the punch penetrates, the faster
it is going, the more it pushes in, the more tissues are stressed, causing
tearing, and compressed, causing contusions. Tensing on impact
reduces this effect also and causes less soft tissue damage.
These experiments were all just re-runs of an old aikido trick where someone puts out an arm,
tenses it up, and tries to resist having the arm bent. But if the person relaxes and just tries to
point forward, the arm is nearly unbendable. This is not because of mysterious energy, but
rather because of efficient use of muscles.
The muscles in the arm that move it forward in the punching action and hold it up in the air
must be tensed to shape the limb and move it. But all of the other muscles should be relaxed.
During such a motion, speed is maximized. As much of the body should be moving with the
punch as possible on impact, not stopped, so that weight is increased. This is the secret of a
powerful punch.
To put a little more oomph in my punch, I learned to -unweight- my front leg a little to
increase the weight that leans on the fist, but that is a topic for another article.
The deltoid lifts the arm horizontal and pulls the elbow upward.
The triceps straighten the elbow. The biceps hold the forearm up by
holding the elbow closed through the motion. The secret to a fast,
relaxed punch is to minimize biceps usage and maximize triceps and
deltoid output until the impact is over. Tensing the biceps (blue) pulls the
elbow closed, reducing the forward force of the punch after it hits a target.
After years of believing that if I tensed on impact my punch would be stronger, I have learned
the hard way that it is not. Efforts to prove otherwise only showed me the depth of my foolish
belief in focus as a concept. Instead, the best way to make a punch is to relax all the way
through and only contract the minimum muscle necessary to prevent the elbow from hyperextending. All other purposeful tension only slows things down and weakens the punch.
This explains to me why many styles of karate in Japan other than Shotokan do not teach
tensing on impact, and why Egami, in his book on Shotokan, recants the practice as well.
Tensing on impact is very pretty to behold, especially if you are programmed to look for it as
proper body dynamics, but in practice, when used on a target that resists, tensing too many
muscles on impact in an attempt to focus is not a very good idea.
However, when I perform techniques, I still very carefully tense the minimal muscles required
to prevent injuring a joint. What if you miss the makiwara or the heavy bag with your punch?
You do not want to over-extend your elbow, so tensing in this limited regard I find very
useful and continue to do. But I only tense those muscles I need to prevent joint injury. If I do
miss, my trained reflex to tense those protective antagonist muscles kicks in before the joint is
over-extended.
How does all of this play into sparring practice? Well, the concept of focus is actually very
useful during free sparring, for the over-tensing just before impact dampens the force of the
strike and lessens any chance you will harm someone else.
However, when executing many techniques consecutively and as quickly as possible,
maximum tension means a slower rhythm and more opportunities for your opponent to get
through, so even here I try to use depth perception and long and often-practiced touch control
to prevent my punches from penetrating rather than over-tensing extraneous muscles in a vain
attempt to increase the impact effect.
For every action there is an equal and opposite reaction.
The target will harm itself by stressing against the punch via the
reaction force. This reaction is instantaneous, and is not aided or
accelerated by leaving the fist in the target after the punch has stopped
moving forward. The reaction only lasts while the punch is pushing in.
Experiment with this concept on your own and make up your own mind. Remember, when
hitting something feels comfortable for you, the strike was probably not truly as strong as you
are capable of. I have found that my strongest techniques are those that feel otherwise.
I am a big believer in the concept of karate and baseball being nearly identical in body
dynamics, even if you include the thrusting straight punch. The back foot pushes, the hips
turn, the shoulders turn, the front foot slides forward a little, the back heel comes up, and the
hands and feet follow through as much as practical without causing a loss balance so that
more techniques or a change of direction can follow. Doing more than this, in my experience,
is not so much practical as it is merely aesthetic.
Now that you have read my conclusions on focus, which I came to very reluctantly, you are
probably feeling pretty reluctant yourself. I do not blame you one bit. It is not easy to go
against the grain, in your own mind, and do something completely independent of what you
have been taught or what you see others doing. When 1000 people run for the exit, the urge is
to run with them, not watch them run and sit still.
I think if, rather than reacting to these concepts in my mind and trying to think up reasons
why they were wrong, I had truly pondered them and experimented on my own, I would have
come to these conclusions with less pain and effort on my part. I now comfortably participate
in any karate training without worrying about focusing, because I am convinced that there is
no such thing.
Below, I have attached some challenges that I have received in the past in support of kime
meaning “maximum body lock down or tension on impact.”
Arguments For and Against
Force = Mass x Acceleration. By tensing the muscles at impact, we are able to make our
techniques fast and heavy because tensing the muscles links body parts together to increase
mass.
Tensing muscles in the arm or the rest of the body, both agonist (those that push the technique
forward) and antagonist (those that arrest forward motion), creates the kinesthetic sensation of
extra mass, but because motion is arrested by the addition of the antagonist muscle tension, in
fact less mass is at work. The mass componment of the equation for force is lessened when
less of the body is in motion.
If you wish to have more of your body weight behind a technique, instead of tensing muscles,
which does nothing, I recommend that you shift your weight so that your front foot is
unweighted as much at possible when a landing a punch. That way, your weight will be
distributed between your fist and your rear foot. Your front fist will keep you from falling,
and your punch will be a punch coupled with the force of you stomping one foot on the floor.
Suddenly arresting forward motion might reduce penetration but increases “shocking power”
by causing the target area to rebound suddenly back into the strongly supported technique.
This second impact causes great damage.
Suddenly arresting forward motion using the antagonist muscles means that muscles that
dampen your ability to push forward to resist any reaction force are at work, and that means
that your support for your technique is actually reduced. Even if the reaction force happened
on time delay like this, which it does not, your technique would be less supported that in
would if you simply continued pushing it forward.
Maximum transfer of momentum occurs when two objects have the same mass. What this
means for karate players is that when you attack a light target like a head, it is bettter to make
your punch “light” and fast. When you attack a heavy target like the torso, it is better to use a
punch that is “heavy” and fast.
You already know this if you think about it: A baseball is light, so when you want to throw it
you keep your arm “light” and swing it as fast as you can. A broken down car is heavy, so
when you want to push it you use lots of “heavy” muscle tension.
This example does not apply to a karate technique, because the goal of a karate technique is
not to push a human body away. A karate technique’s goal is to cause disabling pain or
damage at the location that the strike occurs on the body. A punch to the jaw should break the
jaw, not cause the person hit to fly backwards. That is the difference velocity of a technique
makes. Pushing on something slowly causes the integrity of the body to be maintained so that
it is all pushed backward. Colliding your fist into a part of a big car should dent part of the car
(ouch!), not push the car forward, because that is what a karate technique is for.
I think this example would apply better if the goal were to damage the baseball and damage
the car with the baseball bat. In both cases, you would swing the baseball bat as hard as
possible. The ball, because it is constructed to do so, goes flying. The car is beat to a pulp.
So, it is always best, if you want to do maximum damage, to punch or kick something as fast
as you can.
In order to knock someone out, you have to hit their head and make it snap back so that the
whiplash effect is transfered to their brain, causing them to lose consciousness. Therefore, it is
better to use a different technique to the head than to the ribs or the stomach.
In order to make someone’s head snap back away from your fist instead of breaking their jaw
or cheekbone and leaving them conscious, increasing the surface area that you hit with is
necessary. The smaller the surface area you hit with, the more localized and penetrating the
technique is, and the more likely you are to break something on their head instead of making
their head go backwards. Therefore, instead of hitting with just one knuckle, hit with the flat
of the fist or palm heel. This is why boxers and UFC fighters wear gloves – it prevents broken
jaws and increases the chance of a knock out. Hitting more slowly or quickly or with more or
less tension has nothing to do with trying to knock someone out.
By locking down at impact, you are drawing energy from the floor and adding the mass of the
Earth to your own. This is very powerful.
When you tense antagonist mucles, you are no longer pushing forward off of the Earth, but
instead are now conserving your forward motion and energy. Instead of drawing energy from
the Earth, what you are really doing in this situation is drawing energy from your technique to
create the sensation of tensed mucles on impact. There is no way to add the mass of the Earth
to your techniques. Your mass is constant.
Without getting too technical, something everyone should know is that maximum transfer of
momentum occurs when two objects have the same mass. What this means for karate players
is that when you attack a light target like a head, it is bettter to make your punch “light” and
fast. When you attack a heavy target like the torso, it is better to use a punch that is “heavy”
and fast. You already know this if you think about it: A baseball is light, so when you want to
throw it you keep your arm “light” and swing it as fast as you can. A broken down car is
heavy, so when you want to push it you use lots of “heavy” muscle tension.
Think of a collision between two pool balls. If hit correctly, the first ball can come to a
complete stop after the collision, and the second ball can move away with the same speed as
the first one. In this situation, the first ball has transfered all of it’s mometum to the second
ball. This is possible because the balls have almost identical mass.
Now think what would happen if you replaced the first ball with a bowling ball.
If pushed with the same speed the bowling ball will obviously have an awful lot more
momentum than the cue ball in the previous example, but it will keep moving after the
collision, i.e, it will only transfer a tiny portion of it’s full momentum. This is because the
difference in mass is huge.
What I’m trying to communicate is that we should not simply be trying to generate as much
momentum as possible with a technique, we should be trying to transfer as much momentum
as possible. Depending on the target, it can be more appropriaate to use a fast technique with
more or less mass behind it to do this.
This kind of comparison does not work where karate techniques are concerned. For one, the
bowling ball has momentum and nothing but momentum. My fist is being pushed forward and
is not coasting on momentum into the target. Even as the collision happens, I am still pushing
the fist forward into the target. It is always receiving energy with which to further penetrate.
Another problem with this analogy is that the bowling ball’s mass is known. What is the mass
of a punch? What is the projectile? Physicists disagree on this. Some say it is the fist and
forearm. Some say the entire arm up to the shoulder. Depending on the person, the final
projectile mass could be variable by 100 pounds.
As for the analogy of the automobile, consider that there is no such thing as “heavy muscle
tension.” Instead, you are describing the difference between trying to push something as a unit
away from you and trying to damage some part of it. Give me a baseball bat, and if I want to
beat your car into a junk heap, I do not place the bat on the surface and begin pushing slowly
and powerfully. I swing the bat as hard as I can – for speed – and I twist my hips and put my
entire body behind it.
Usually analogies that try to prove the usefulness of focus that utilize baseball are made
without having actually played the game. In baseball, a lot of body weight is put behind the
bat – not in linear fashion, but by swinging with not just the arms but also with the entire
body.
Using momentum transfer to describe a punch hitting a person is impossible. What is the mass
of the target? The body? The rib? How much of an arc of the rib? The mass of the underlying
tissue? Don’t ribs vary in mass from person to person? What about when hitting the stomach?
What is the mass there, since no solid bone exists to be measured, and instead all we have in a
large mess of soft tissue?
Trying to put physics equations to work to determine the best type of karate technique is a feat
of engineering that humanity is not yet capable of doing. When confronted with a person taht
wishes to do me great harm, I plan to punch and kick as fast and hard as I possibly can, not
carefully measure my techniques against their targets and risk getting myself killed as I try to
perfect the transfer of energy into a target. Hit fast, hit heavy, hit hard.
How to Make a Front Stance
by Rob Redmond - September 10, 2006
The one thing so many people commented upon when I returned home from Japan was that
my stances looked like they had been completely overhauled. They were deeper, though not
really longer, and I looked and felt more comfortable in them. I believe this increase in stance
competence mostly occurred because, as I have written before, here in the US, most basic
training is in basic techniques marching up and down the floor. Very few people actually train
actively in the fundamentals on a regular basis, breaking techniques down into their
component motions and training those motions.
Oh, sure, we do that for beginners, but in Japan I found that most classes involved breaking
techniques down even when the room was full of 3rd dans. The “Isolation Training” I learned
from Katayama Sensei wasn’t for learning a technique. It was for practicing techniques. The
more it is performed, the more technical skill develops quickly, in my opinion.
Making excellent stances is a great way to improve not just the appearance of your techniques
after you finish a step, it is also a great way to improve your stepping speed and accuracy,
your footwork, and to give yourself something to land on when you finish a long, lunging
technique.
Stances Are Landing Gears
The most important thing to understand about stances in Karate is what they are for. What is a
front stance, specifically? I believe most people have this backwards and think that the front
stance is a launching posture from which strong techniques can be thrown forward. When
they think of a front stance, they think of steps, reverse punches, and rotational blocks all
shooting outward and whirling about them with their firmly rooted feet pushing into the floor
to power their legs and hips.
I don’t view them that way except in a limited set of scenarios.
I instead view the front stance as a landing gear. The stance is the position my feet and legs
take up to catch me at the end of a movement in which my center of gravity travels in any
particular direction. I believe that my legs and feet are serving the same job that the tires and
landing struts of an airplane serve as it is coming in for a landing.
Think about a stepping punch. Do you have to launch it from a front stance, or aren’t you able
to launch it from any position? Look at the beginning of every kata. Most of them involve
standing upright and then suddenly executing a technique to the left or right from that posture.
The stance comes at the end of the technique, not at the beginning.
It’s a posture to catch yourself from falling after throwing your center of gravity in a direction
powerfully, not the bottom half of a tank. Looking at every motion we make in sparring and in
kata, I don’t see many rooted actions which take advantage of the stance as a launching
posture. I see mostly stances that result from techniques that have already happened when
stepping is involved.
This is an important topic, because you get better results from training if you have a goal in
mind for your stance and work in support of that goal. A stance that you think is a launching
pad or some sort of rooted support structure for standing your ground, something that I
believe would never, ever work in an actual fight, by the way, is going to have different
tensions and execution than a stance that is the posture you assume to best arrest yourself after
a violent motion.
Stances are landing gears. They are the postures we take to put on the brakes.
The Qualities of the Front Stance
What shape should the front stance take if we are putting on the brakes with it?
I would love to be able to give you exact measurements and proportions for making a perfect
front stance. It’s too bad that I can’t. Human bodies are very unique. As an instructor, I would
have to look at your stances in particular as performed with your body, and then based on a
direct visual assessment, move your feet and knees around until I liked what I saw. Then I
would keep moving your feet and knees back into those positions during static stance training
every time you trained with me to habituate you to making that exact stance consistently.
If there is one important point about stances, it is consistency that will make them or break
them. Doing the same thing every step you take is really the ultimate skill, because the last
thing you want to spend time doing is thinking about where to put your feet from one step to
another. Until you can do this, you won’t have enough free brain cells to focus on the rest of
the technique.
The body parts that go into a good stance are:
Stability – We want our stance to be relatively stable because the purpose of it is to
stop our center of gravity from moving about until we are ready to break the stance
and allow it to move.
Braking ability – The stance has to bring us to a halt.
Mobility – The stance must allow itself to be broken easily when we wish to move
from one lunging motion to another, change directions quickly, or suddenly begin
moving. If we are frozen in place, our opponent will see us coming from a mile away
as we struggle to free ourselves from too rooted a position.
Hard to believe that those few requirements could result in us making something as ridiculous
as the Shotokan front stance, isn’t it? But it does.
So, what is a good front stance? I cannot point you to some particular person as an example. If
I were coaching you on your golf swing, I wouldn’t say, “We are going to do it like Arnold
Palmer.” He has his own personal golf swing that technically is not proper form for maximum
effectiveness – but he could always make it work better than most people’s. So, I’ll just give
you some guidelines and reasons for each of those guidelines.
Front Stance Dimensions
Stances exist in three dimensions. Thus, your stance has length, width, and height. Most
people seem to make their stances too short, too high, and too wide in the Shotokan
community. If you look at Tae Kwon Do and American Freestyle (which are basically the
same thing), they tend to make their stances too long, too wide, and too low. I believe there is
a sweet spot for the front stance. And there is more after that.
First, the length. It depends on how long your legs are. The longer your legs, the longer the
stance. Here is some bad news for everyone: there is such a thing as optimal leg length. Some
people have such long legs that the stance cannot be pushed deeper without harming mobility,
so these people must assume a higher stance. While it will be equally effective for our
purposes, it is not as pretty because the human eye prefers certain angles to others when
looking at human postures. Some people have such short legs that they cannot push their
stances too deeply either, or they risk being so low that they are staring at their opponent’s
knees. Thus, they too have to make a higher stance.
What is this? I’m talking about length, not height! The length of the stance determines the
height.
I am 72 inches (183 cm) tall and have a 30 inch (76.2 cm) inseam. I make my front stance 49″
(125 cm) long from my rear heel to the tip of my front big toe.
What about the width? There are lots of odd rules out there for how wide a front stance
“should be.” I say “should be” in quotes like that because there is no “should be” when it
comes to Karate techniques. Those two words are used to enforce arbitrary rules. They are not
used by people who are interested in finding out what is truly effective for themselves and
others. There is no “should be.”
Some of these rules are 1.5x shoulder width, hip diameter, and other such measurements. I
don’t listen to any of those rules. I make my front stance around 14″ wide as measured from
the inside of my rear heel to the inside of the innermost portion of my front foot.
So, it looks like this:
The dimensions of my front stance
Why do I make my front stance to these dimensions instead of longer, shorter, wider, or
narrower? The constraints I listed above are the explanation. My stance is long enough to
make a good finish to a nice, deep step forward. It gets me low enough to the ground that I am
stable enough without sacrificing too much mobility. it is just wide enough to allow me to
rotate my hips in place.
It is also narrow enough that my rear foot is behind my forward motion. If I made the stance
any wider, my rear foot would be off my rear flank instead of almost directly behind me, and
it would be pushing at an angle that wouldn’t help a punch or kick directly in front of me.
This stance also is a result. Remember when I wrote that stances were landing gears? I put
myself in this position as a result of stepping or shifting forward. This is how I step forward. I
only move the foot in a shallow inward and outward movement – focusing almost entirely on
directing my foot forward without causing my rear heel to lift.
It’s stable, mobile, and flexible and gives me braking ability. This stance meets all of my
requirements for a good front stance.
What can I compare it to in order to derive some possible advice for structuring yours?
It is precisely the width of my hips. I didn’t use my hips to determine the width, it just
turns out that way.
It is 75% the width of my shoulders.
It is 3.5 times as long as it is wide.
It is 4.5 times as long as my feet are long.
Like you, I have been told all sorts of arbitrary rules for constructing my front stance.
“Shoulder width” is one that I have been taught before. I strongly disagree with that. With
your feet that wide, it is easier to rotate your hips, but your back leg isn’t pushing forward to
do the rotation, and if you try to step forward, you’ll be slowed down by using weaker, inner
muscles to pull the leg inward and then push it outward again making ridiculously wide Cshaped steps.
I’ve also been told that it should be as long as double shoulder width. I think that is too short
for my purposes of supporting a solidly long step forward without over-extending as if in a
sparring match with the heel up.
I cannot tell you that these dimensions will work perfectly on you. But you can see the overall
shape of it and resolve it down for yourself, getting an idea of how wide it can be vs. how
long. And, I can only offer you my opinion as to what the right dimensions are. Truly, there is
no rule, there are only preferences. This annoys people who want firm rules to follow. There
aren’t any. This stance works for me, and I’ve been told it doesn’t look too bad, either.
You will have to develop your own working with the requirements you have for your stance’s
performance.
Shaping up the Front Stance
The position of the feet on the floor plus a bend at the front knee is not sufficient detail to tell
us how to shape our front stance above the feet. We also need to know where the plumb-line
is on the floor beneath the knee, otherwise we don’t know how far to bend our knee.
I try to put my knee cap directly over my big toenail, so my shin ends up nearly straight up
and down.
As seen from above, the position of my hips and front knee are related.
I’m not a big fan of putting my knee inside my front foot and collapsing my leg inward. When
I do that, my hips move sidways more behind the front foot than in front of the rear foot. My
goal is to keep my rear foot directly behind its own hip socket. That way, when I rotate my
hips, I’m not pulling my hip from the side, but simply pushing into the floor by straightening
my knee and flexing my buttock to turn the hips.
Moving the plumb line of the knee to inside the foot moves the hips
too far to the side.
A lot of people like to turn their front foot inward in a front stance. I think they do this either
because they pull their knee inward and it causes the outside of their front foot to raise, or
they are just doing it because someone saw someone else do it and they think “it is the proper
way.”
I can’t see any advantage to it, and when I put my knee cap over my big toe nail, I find that
turning in my front foot strains my ankle and takes the weight off of the sole of my foot and
puts it all on the outside edge.
But I especially don’t like the lateral strain on the ankle and knee this causes from catching
my body weight every time I step.
Turning the front foot inward I find to be pointless, and it contributes to putting
the hips over to the side.
If you are even thinking about this sort of thing, you are already ahead of most people. Most
people never think about the shape of their legs in between the hips and the feet. They don’t
worry about knee placement, they only worry about foot placement according to some rules,
and they just let the rest fall into some random place.
As for the rear foot, some people get obsessed with the outside edge of the rear foot touching
the floor. This really isn’t that important. It’s just nice looking more than it is functional. Keep
in mind, as you step forward, after the rear foot has pushed and the hips are moving forward
during the last portions of the step, the rear foot doesn’t have any energy left in it, and its
contact with the floor is now irrelevant.
The only reason we keep that rear heel down is because it looks good. It doesn’t really help
anything in a step. More about that in an upcoming article about stepping in a front stance.
Likewise, don’t get caught up in the angle of the rear foot. If your foot turns out to 45 degrees,
that’s perfectly normal, and again, it doesn’t hurt anything. The only reason to keep it facing
forward at all is so you can step quickly out of the stance and move forward without resorting
to the weak muscles on the inside of the rear leg.
It has been my experience that good stances come from having to stretch certain parts of my
body to accept the stance. At first, I feel off-balance, but with time practicing the stance, it
settle into it. How do you do that?
Stance Strengthening and Stretching
My experience has traditionally been that of participating in classes where a lot of static
stretching, involving bending over and pulling on my feet, etc, has started the class off.
However, I have since learned that doing static stretching at the beginning of classes doesn’t
really help me very much. I save it for the end of my practice sessions. Instead, I do dynamic
stretching – leg swings – to warm up and stretch my legs before I practice. But I have one
exception.
When I am going to do stance training, I always start off by assuming that stance and standing
in it for at least two minutes, then switch legs, and repeat the two minute timer. During that
time, I try to relax certain parts of my body and tense others. I also avoid moving my legs at
all, and enjoy the fact that this exercise, more than any other, stretches out the ankles good
enough for excellent stepping training.
Some people might say, “Two minutes, that’s nothing. I can stand in a front stance for an
hour!” I’ve seen those stances. They don’t use anything approaching the dimensions that I
provided above. A good front stance will start to burn after about a minute. After two minutes,
your thigh muscles should nearly reach exhaustion, you will feel a burning sensation, and the
muscle will begin to quiver as it runs out of steam to continue the action.
This sort of stance training is an isometric contraction. It shouldn’t be bad for your joints.
Although I am not a doctor nor a health specialist of any kind (my background is in business
management), I’ve read in a few places that doctors often treat joint strengthening with
isometric exercises where the joint is stationary and the muscles and tendons have a load put
on them.
Do your own reading, consult a physician and find out what works for you before you try this
drill on your new, artificial knee or old sports injury, OK? Don’t blow your knee out and then
write to me saying it is my fault.
Stance training is time-consuming, it burns, and it’s boring. I do this kind of thing about once
a week these days, but beginners should do this kind of training during every session in order
to develop excellent stances.
Summary
Stances are landing gears. The front stance catches our weight as we move forward, and it
holds us up when we stand with our weight projected forward.
I Do Not Believe in Ki
by Rob Redmond - October 11, 2005
Since I began training in the martial arts as a child, I have been told of the mysterious powers
of ki. Ki, known to Chinese as chi, is often cited as being the source of the mysterious abilities
of master martial artists. They are supposedly able, through force of will and concentration
combined with physical techniques such as breathing properly to channel the very energy that
flows throughout all living things. They can, according to some, inhale this energy from other
living things and the world around them, and then can funnel it into a laser point in order to
give themselves increased physical performance, devastating punches and kicks, control over
other people’s psychological states, increased sensitivity to others, and ultimately telekinetic
abilities that allow them to levitate objects from a distance.
I wasn’t told all of that by one person. I picked up part of it here and part of it there, and like
most kids who take karate throughout their lives and into adulthood, I carried in my mind both
the original ideas I learned and others that I extrapolated from what I had been told. I read
books, because if things are in writing they are obviously true, about ki power and how to
increase it and control it. I never questioned it until I reached adulthood.
I want you to know that I believe in ki. I believe it is there just like I believe in the walls
around me. The reason I believe so strongly in ki is that I use the word the way it is used in
the standard Japanese language: energy. I believe that when I feel energetic, that I have strong
ki. When I feel sick, I have weak ki. Strong and weak ki are strong and weak energy. Ki
means energy.
KI – (n.) energy
I don’t believe that ki means telekinetic energy, nor do I believe it is special energy that I can
channel within my body to heal or push out of my body to perform acts of telekinesis. It is
just energy, plain and simple. When I feel like a million bucks, it is because I got enough
sleep, I’m relaxed and unstressed, I am psychologically motivated and happy, and I have been
eating well. To me, that is ki, and I see absolutely nothing wrong with believing in ki in that
way. I cannot prove to you that ki does not exist, because I believe it does. I had some good ki
this morning, and I revised this article for the umpteenth time and put it in the queue to be
published on my web site.
However, I do not believe that ki means special energy flowing through meridians in our
bodies. I do not believe that ki is like The Force from Star Wars, something that I can harness
and use to increase my strength, speed, or make objects move without touching them. I do not
believe that ki is transferred from one person to another, projected outward, nor that it glows
and that only the special people who sell psychic advice can see it. I do not believe that ki is
anything other than a combination of my psychological state, food intake, brain chemistry,
and physical health and completely internal to me.
I should state up front that I am not an atheist who gets his jollies by annoying people who
have spiritual beliefs by trying to disprove everything they believe. On the contrary, I am a
deeply spiritual person, and I believe in many things that I cannot prove to others or which
might not make sense to them.
In this article, I will explain why I do not believe in ki as a force that can be channeled, seen
felt, touched, or used like a psychic or telekinetic force. But I will not prove that there is no
such thing as ki, because I believe there is. I will also not attempt to prove that there is no
such thing as a telekinesis, meridians, projected ki power, or anything else of that ilk. I will
not attempt to prove that because it cannot be proven, and I will explain why attempting to
prove that something does not exist is an irrational, illogical, and impossible act.
That may read as unreasonable to people who are used to trying to maintain open minds and
feel that it is dangerous to take an idea like ki and just throw it out the window. But I have
thrown it out the window, and if you are curious as to what my reasoning was, I will share it
with you.
Proving the Unprovable
Are you aware that there is no such concept as proving something does not exist? I went a
large portion of my life without being aware of the fact that scientists will reject out of hand
any attempt by anyone to prove that something does not happen or does not exist. That is
because it cannot be done. Instead, if faced with a concept that they wish to test the validity
of, scientists will test the evidence for it, and if the evidence fails the tests, they will assume
that because no evidence exists for it, that it must be an invention, hallucination, or deception.
A fundamental scientific principle is that any hypothesis put forward must be defended by the
person who puts it forward. It is not incumbent on those who disagree with an idea or think it
is wrong to disprove it. There are two reasons for that. The first reason is justice. It makes no
sense at all why everything that everyone thinks should be assumed to be true until I run
around so much that my pants start to fall down around my ankles attempting to disprove
them all. So, generally, the default belief that scientists hold is that any idea is untrue until
shown to be otherwise.
The other reason that the burden of proof is on the believer is because it is impossible to prove
a negative. I will demonstrate. Let’s say that I claim there is an invisible snarg on my
shoulder. He’s 4 inches tall, round, purple (despite his invisibility), and he has rather large
eyes. He’s covered with fur and quite cuddly. He has little antennas and feet, but no hands. He
hops around a lot, but he doesn’t make any noise. I know for a fact he’s there. The sacred
scrolls say he is there. My karate teacher says he’s there. And I once saw a magician who was
able to perform a card trick solely because of the power of his invisible snarg. I’m convinced.
Meet the Invisible Purple Snarg.
Now, we both know for a fact that there is no snarg on my shoulder. My shoulder is empty,
nothing is there. With or without the presence of snarggage, I’m probably able to do the
things that I do. It seems unreasonable to assume that the story about the snarg is true, doesn’t
it? Therefore, there is no snarg on my shoulder. We both know there isn’t one.
Prove it. Prove that there is no snarg. There isn’t, so it should be easy. But it’s quite
impossible. One cannot prove that something does not exist.
Therefore, most scientists, and I say most because there are more than a few folks out there
who say they are scientists but are really little more than political puppets, most scientists
require the believer or proponent of an idea to be the one to prove the positive. Prove to us it
is true.
The rigor for evidence is not that strict, so there is little excuse for there being an effect that is
completely undocumented. Scientists generally are not looking for absolute, infallible proof.
They are curious anytime they see supporting evidence of any kind that points to something.
Show a scientist something you have observed and any meager hints as to what could be the
cause, and he will be very interested to investigate it.
But generally, a hypothesis does not graduate to theory, principle, and finally law until very
careful controlled experiments of all kinds have been performed to remove any other possible
causes for the effects observed. Those experiments must be carefully documented so that
others can perform them from the journal entries, and the results must be similar in diverse
locations before the results are considered significant.
So often our news media states that “a new study shows” before this replication of results has
been performed, misleading us to believe that some new knowledge of the universe has been
acquired when in reality a man with a hunch performed an experiment improperly and hastily
reported his results so he could get back to his joint and magic show.
When no supporting evidence can be found, the default is disbelief. When no effect at all is
observed, the default is that the hypothesis is irrational and unreasonable.
The whole point is cause and effect. You see an effect, you hypothesize about the cause. You
try to control any extraneous variables, and you try to work your way down to what the cause
really is. If the experiment is a success, it will either point toward your hypothetical cause, or
it will point to another cause. Either way, the cause of the effect is eventually found.
The scientific method, as I have written elsewhere on this web site, is a very harsh way to run
a human mind. I do not operate my mind in this way. I choose to believe the things that make
sense to me and that are consistent with what I already know to be true. I trust also in my
personal experience, because to deny it is to doubt myself on a fundamental level that would
lead me to the logical conclusion that the world around me does not exist, life has no
meaning, and I may as well be a mass murderer as a saint. I don’t like that sort of solipsism
and refuse to engage in it.
So, I am not suggesting that all of your beliefs about the creation of the Universe, the
existence of God, the nature of reality, or your morality and ethics be pushed through a filter
requiring evidence beyond a reasonable doubt.
What I am suggesting, however, is that the invisible snarg is an obviously unreasonable belief,
because you know for a fact that I just made it up for the purpose of this article, and there is
no reason to believe it exists.
The next step we will take in this discussion is to differentiate between religious and spiritual
beliefs and false beliefs about reality which are unreasonable because of the lack of evidence
and the inability to prove that something does not exist.
Cause and Effect
The difference between believing in ki as a telekinetic force or a channeled energy that only
the chosen few can see and the belief in various theist religions is that no one has come up
with an observed effect for which ki is supposedly the cause. There is nothing happening out
there in the world that needs ki to account for it.
We have a reason to have the idea of God. God explains many things about the world for us.
Whether you believe in God or not is unimportant. What is important is that there is an effect
for which God is a possible cause. There is a universe. It exists. We are led to wonder what
caused it to come into being, and what inspired life on our planet. Some believe that the
explanation is chance combined with chemistry and physics, others see a supernatural
presence at work. Either way, there is an effect, and man searches for the cause and guesses as
to what it might be.
When asked for examples of effects for which ki would be the cause, the following are
usually cited.
High Levels of Martial Skill is sometimes credited to an ability to harness and manipulate
hidden flowing energies. However, physical training and other factors are better explanations
for which we possess mountains of evidence. There is no way to remove these causes for the
effect of good skills in the martial arts, therefore it is impossible to find another cause. In
order to assert that ki were to be credited for martial arts abilities, someone would have to
demonstrate an effect for which there could be no other cause in order for ki to be a
reasonable explanation. For example, if a martial artist could levitate in a laboratory and on
demand anywhere anytime, then we might speculate as to the cause of this effect.
Accupunture’s Effectiveness Against Pain is sometimes shown as evidence that there is ki.
But, this has been shown to be a physical effect on the way the nervous system behaves. At
some point in their history, the Chinese came up with “chi” (or borrowed the idea from
someone else) as a life force that flows through the body which acupuncture is able to affect.
They were trying to explain the effects of acupuncture and other things, and they were
operating in the dark, so they came up with ki as a reasonable explanation. However, we now
know the real cause. Thus, this is no longer a reason to believe in ki because of this effect.
I could go on naming other effects such as feeling tingly when someone is standing near to
you, the parlor tricks such as “unbendable arm”, the one-inch-punch, breaking boards, and
other nonsense. The point is that there is nothing we observe in our world which calls for ki to
explain it.
This concept is difficult to explain, but it all comes down to this: If there is not something that
needs ki to explain it, then coming up with ki first and the thing it causes second is usually
evidence of invention, hallucination, or deception.
Therefore, it is irrational and unreasonable to believe in ki, since there is nothing that you see
in the world as an effect which cannot be explained without using ki to explain it. For those
things we do not understand, ki does not explain them. For the effects that ki can supposedly
have, there is no effect. Believers in ki do not live longer, are not healthier, are not happier,
are not free from psychological and emotional trauma, and most importantly, they cannot
demonstrate anything that would lead one to say, “Look! Some ki!”
A Challenge to Anyone to Prove Ki Exists
Don’t take this article the wrong way. I sure do wish there was such a thing as ki. After all, I
have tons of martial arts training behind me now, and if anyone were going to ever learn to
use their ki energy, then I would be one of those people. I would love to be able to flick on the
lights in my office without clapping my hands twice. I would love to be able to raise a hand
and push my opponents back like Jedi. I would love to pull objects to me, make things float in
the air, and punch through steel walls. I wish it did exist. It would be wonderful!
So, please, if you think you have the ki power that everyone else wishes they had, prove it.
For once and for all, put everyone else in their place. The James Randi Educational
Foundation offers a $1,000,000.00 purse to anyone who can, under scientific conditions and
observation, perform any form of supernatural or psychic act. So far, none have ever won the
purse. None have even come close. In fact, I am disgusted to report to you that no one has
managed to do anything while attempting to win the purse except utterly humiliate themselves
and come away looking like a fraud.
It’s amazing the levels of denial and dillusion that we can live with without even realizing it. I
witnessed this while watching a television program hosted by James Randi in which various
famous psychics attempted each to win the $1,000,000.00 prize. Each was allowed to
negotiate the conditions under which they would perform as long as they did not interfere
with scientific observation and recording. The psychics each agreed that they could easily
perform their feats of supernatural powers under the conditions to which they had consented
before the tests were run. I watched these people on television one after another answer
questions and repeat, “Yes, I can do this. Yes, conditions are perfect. Yes, this will be no
problem. I’m good. Let’s get to it.”
One performer was a psychometrist. He claimed that he could hold objects and learn about the
people who owned them. He agreed to have ten people remove their watches, put them in a
bucket. Have the bucket stirred, and then he would hand the watches back to the appropriate
people. Randi’s folks imposed a condition upon his demonstration that he not be allowed to
see the people he was going to give them back to so that they would not react facially to his
picking up their personal watch. Each of the subjects had a hood over their head. As you can
imagine, when the hoods were raised, no one had the right watch. At least the women
received women’s watches and men received men’s watches, but other than that, he was dead
wrong and every reasonable person who saw him perform that night knows he was proven to
be either deluded or a liar.
I believe he probably was not even aware that he was watching people’s faces for their
reactions. He was perfectly agreeable to covering their heads, and yet suddenly his special
powers evaporated. Oops.
Next!
Another claimed to be able to see auras. She agreed to a test where a 6 foot wall of thin
partitions was placed in front of her. There were ten numbered spots. She claimed that the
“head chakra”, a floating ball of energy she claims she sees over everyone’s heads which is
composed of ki or chi, floated higher than six feet and she could see it easily if people stood
behind the walls. The scientists chose a random number of people to stand behind the wall.
She required the area be bathed in orange colored lights to clear out any residue energy before
the people lined up. She turned around, she looked at the spots one at a time, seeing the head
chakra points, supposedly, and guessed that there was a person behind every number.
The partition was dropped. No one was there. She had seen nothing. Perhaps she forgot her
special pill that morning. She too was humiliated, and anyone watching her that night,
including me, shook their head and wondered, “Why the heck would she agree to be tested on
TV, and why would she set up conditions she herself could not operate under”? Money, that’s
why. $1,000,000.00 is a lot of money, and her clientele probably were not watching that
channel that night anyway. I guess she and the others figured that they may as well try.
Next!
No one has claimed the money, and that includes supposed ki believers walking around the
world today selling books on ki and chi, claiming that they can suck special energy using the
power of their thought alone off of plants and put special energy into their sick relatives.
Jargon Gone Mad
When challenged, some point to ki as being not an explanation of any paranormal activity, but
rather that it is a handy catch-all term that encompasses the mundane. For example, one
instructor said that ki only represents good mechanics and solid training. Another wrote, “It is
just your life force that is the manifestation of all the electro-chemical reactions going on in
your body. It’s energy – that’s all.”
Well, that’s fine. I believe in all of that. However, I don’t feel the need to dress it up in a
fancy suit by using the Japanese word for “energy.” Besides, it reads like excuse-making to
me. It sounds like someone has been using the term ki in their karate instruction, the same
way they heard it, and they are not quite ready to admit to themselves that using it has not
been a good idea. It reads to me like political weaseling, “I voted for that bill, but only
because I believed it would not pass.”
“I say ki all the time in my classes, but I don’t mean anything other than the normal
expression of energy that you said you believe in.”
Fine. But then why not use the English word?
I think it is unwise to use a paranormal sounding term, especially a term that many people
firmly believe to refer to supernatural activity as some sort of verbal shortcut. The real
explanation is no more difficult than the initial training in jargon, so there is no true gain in
efficiency. Instead, the only thing that is really accomplished is that some karate instructor
continues using a bogus jargon word in order to sound and feel wise and knowledgeable
which hinders accurate communication and potentially exacerbates the misinformation and
paranormal belief to which so many are already victims.
This seems to be an apology for the use of the vague, meaningless term “ki”, which in
Japanese means “energy”, as in “I feel energetic” (ki ga tsuyoi) vs. “I feel tired” (ki ga nai).
There is no English equivalent for the catch-all idiomatic expression “ki”.
We have English expressions for efficiency, being in the zone, psyching up, digging deeper,
and other things like this from our own sports. I believe using the term “ki” leads to these
false explanations and beliefs in magic energy forces tapped by acupuncture needles and then
broadcast out over the airwaves to convince us that we never really went to the moon and that
Elvis is alive.
I cannot prove that there is no telekinesis in the world, no chakra points, no meridians, no
channels , but then I do not have to. I am not claiming that there is such a thing. The burden of
proof is upon others to demonstrate their ki power. I would even feel more open to the
possibility of the existence of this special energy that can be directed, focused, and harnessed
beyond my biochemical and mental processes if someone could come up with any excuse for
it to exist. What does it do?
Does this special power really exist and yet accomplish nothing?
I do not believe in the paranormal explanations of ki, but I do believe in ki being regular old
energy. I prefer to avoid any confusion that it might cause to use the Japanese word for energy
in my karate classes, so I use the English word for energy when I feel the need. But to be
honest, that need never arises, because people’s energy levels are their business, not mine.
The only time I might use it is when I am feeling tired. “I don’t have a lot of energy today.”
That is the limit of my experience with ki.
Some will protest that they have seen something that used ki. I say you were tricked. You can
demonstrate ki? Take the money, then tell me about it. If I ever find that I can telekinetically
manipulate the world around me, you will know it. This web site will be replaced with a
single page that reads, “I AM A TELEKINETIC MILLIONAIRE!”
http://www.randi.org is the James Randi Educational Foundation. James Randi is a magician who
specializes in exposing fraudulent claims of psychic ability. He is a skeptic, and offers $1,000,000.00 US
to anyone who can demonstrate any abilities at all. All who have tried have failed miserably.
Thanks to Guss Wilkinson of the Hamilton Bugeikan Karate Club New Zealand for the idea for this article.
http://www.aikiweb.com/language/ki_phrases.html Shows phrases in Japanese that show the ancient
use of the word supplanted by modern idiomatic expressions. Instructor disavows the paranormal.
A great book for learning how the scientific method works and why things like healing crystals, tarot
cards, astrology, and ki power are not reasonable beliefs is The Demon Haunted World by Carl Sagan.
Karate as a Science: A Comment on Extension and Fist
Rotation During Punching
by David Krueger - December 21, 2008
As commonly practiced and taught, Karate is not a science. This does not mean, however, that
the laws of physics cease to apply to martial arts techniques. While karate is not a science,
karate can be scientifically examined. In fact there are, albeit very few, peer-reviewed
published articles that examine the physics of punching in karate, and that also have
implications for some commonly held beliefs. See FN1.
Issue 1: Does full extension create the strongest punch?
One of the more common physics debates in karate relates to proper punching. In this debate,
there are two common schools of thought: 1) karate punches are strongest at full extension
and teach “following though” as a power component; vs. 2) karate strikes are strongest at
approximately 75% extension. I put the information from Walker (FN1) forward not opining
my own calculations, but merely to report the results of this article and synthesize the stated
results with common practice.
Contrary to the commonly held belief regarding force/impact at maximum extension and
“tensing on impact,” an examination of karate punching from a high speed camera shows that
punches reach maximum speed before the arm is fully extended. Applying this speed to
deformation analysis, Walker states:
[W]e are not so concerned with the efficient transfer of energy to deformation with each strike
as we are with the absolute magnitude of the energy transfer. * * * Maximum energy
transferred to deformation would occur if impact is made at that 75% point.
Id. at 846.
While aspects such as velocity, acceleration, etc., are all relevant in analysis of a punch, it is
deformation (the change in the the shape of a target due to an applied force) that karate
players are ultimately concerned about when discussing the power/strength of a punch.
Explaining the results, the article states:
* * * If we assume constant acceleration and deceleration of his fist and if we used the time of
maximum fist speed given above [.02 sec punch with max speed at approximately 7 m/s] then
the maximum speed is reached at 0.75 of the arm’s full extension, or typically 10-14 cm from
the stopping point.
Id.
A corollary misconception regarding full punch extension is the concept that “following
through” is beneficial to damaging an opponent. However, for the same reason that a fully
extended punch is less powerful than a punch at 75% extension, “following through” similarly
does not increase the deformation power of a punch.
In street fighting there may be a continuation of the punch after maximum speed is obtained
and even after contact is reached. * * * [I]f contact is made just as the follow-through begins,
then the energy transfer during the follow through results from pushing, and since pushing
and displacement do not result in deformation damage, they are not normally worth the loss in
the attacker’s poise.
Id.
These results are easily synthesized with the practice of punching “behind” (or the inside) of
an opponent. When instructing students how to break boards, it is a common to teach the
student to aim the punch behind the board several inches. Contact occurs when the punch can
cause the greatest deformation damage; before the punch is at full extension.
Accordingly, this teaching practice is consistent with the results of Walker, supra,
demonstrating that a punch’s greatest deformation damage occurs prior to full extension or
any follow through of a punch. Note: Aiming a punch inside/behind a target does not
constitute follow through, which cannot occur until full extension is achieved. Even viewing
“follow through” as punching until full extension, however, is still inefficient because as
outlined above 1) maximum deformation transfer will already have occurred upon contact and
2) any follow through beyond approximately 75% extension is significantly less powerful.
See id. at Fig. 2.
While as a matter of form the karate player may punch to full extension, as a matter of physics
a punch yields less deformation damage at full extension than it does at approximately 75%
extension.
Issue 2: Does rotating the fist make a punch stronger?
Another common technical discussion amongst karate players is when, if at all, a person
should rotate his first during the course of a punch. Some advocate that rotation of the hand
does not increase the strength of the punch. Others argue that fist rotation increases the power
of a punch, though there is disagreement over where the fist should be rotated during the
course of the technique (either rotated immediately before contact or during the entire punch).
Discussing the impact of rotational energy on a punch, the article continues:
Introductory karate students often believe that the rotation of the fist in the forward punch
described above significantly adds to the energy delivered to the opponent. * * * [Applying
the calculation, however,] we find that the rotational energy Er is [0.4 J], which is negligible
compared to the 156 J calculated before. Similarly negligible results are obtained for
punches in those styles of karate in which the fist if rotated immediately before contact
rather than continuously throughout the punch.
Id. at 846-847 (emphasis added).
If you are interested in the full calculations, feel free to find the article. The results are clear,
however, that rotation of the fist during a punch has virtually no impact on the power
generated by the punch itself. The energy generated by no fist rotation, rotation throughout
the punch, and rotation immediately prior to contact are all virtually identical. Fist rotation is
a matter of personal preference and while rotation may feel more “snappy” or powerful to
some, fist rotation does not actually contribute to the speed or deformation potential of a
punch.
Admittedly, the American Journal of Physics is geared toward teaching physics and is not
intended to be a research journal. However, it remains a peer reviewed journal that is still
better researched, better supported, and ultimately more authoritative than almost any opinion
a passing karate player has rendered on the physics of karate punches. In fact, an article in the
American Journal of Physics is actually much more appropriate for karate practitioners than
another physics journal, since it is written toward teaching physics principles.
Ultimately, while there may be other ways to make a punch more powerful, full
extension/follow-through and fist rotation are irrelevant to this issue; they are purely matters
of form, and not of power.
FN1. J. Walker, Karate Strikes, Am. J. Phys., 43:10, 845-849 (1975).