Like Judo, Aikido is a martial art that demands an intuitive understanding of the physics of forces, torques, stability and rotational motion. This article examines a few of the basic aikido techniques. The grace that each requires is not easily conveyed, but each technique can be broken into components that can be examined in terms of classical physics. The experiments I shall describe call for actual performance of the technique, but you should do them only under expert supervision since aikido if performed incorrectly can be dangerous to you and your opponent.
Aikido is similar to judo in that it seeks to overcome the opponent’s stability. Aikido, however, is a relatively modern form of martial art that incorporates techniques from a number of other martial arts.
It is distinguished by its firm code of avoiding injury to the opponent. Hence it is a form of self-defense rather than a sport like judo.
It involves no techniques that can be regarded as attacks. I think it is the most difficult of all the martial arts to learn. Its demands for skill, grace and timing rival those of classical ballet.
Aikido employs many of the
same principles of physics that are found in
Judo. Suppose your opponent grasps you by
the wrists from behind. In one aikido
maneuver you smoothly lower your body while
bringing your wrists upward and over your
head toward the front.
Your opponent hangs on to your wrists but
is brought forward by your descent and
slight lean forward. His position is
therefore unstable because his center of
mass is now slightly forward of his feet.
You draw your right leg backward and drop
onto your right knee. Your arms and torso
are brought forward and downward in a large
arc. Because the first part of the motion
induced your opponent to hold tightly to
your wrists, he is now thrown over your body
in a front somersault.
As in much of aikido, your opponent
actually throws himself. He cannot prevent
your forward motion because of the unstable
posture in which you initially place him.
Even if he has superior body weight, he
cannot stop the motion by pulling downward
on your raised wrists. In such a position he
can pull only along the length of your arms.
The torque due to such a pull is zero
because there is no “lever” (described
in Part I in this series, “The Physics Of
Forces In Judo: Making The Weak Equal To The
Strong”).
Remember, the lever is the perpendicular
from the pivot point (in this case your
shoulder) to the line through the force. The
line through the opponent’s pull passes
through your shoulder and therefore has no
lever arm. Even if he is heavy or strong, he
cannot rotate your arms once you have them
properly over your head.
Many of the techniques in aikido employ
the deflection of a force directed at you.
Suppose your attacker throws a punch at your
face. To stop the punch directly requires a
large impact force which could cause injury.
A wiser technique is to deflect the strike.
Although a large force is necessary to stop
the punch directly, only a small force is
needed to deflect it.
Although most followers of Western style
fighting consider an attack to be an
advantage, in aikido the attacker is at a
distinct disadvantage because of the
momentum of this strike. You can use his
momentum to throw him to the mat.
Suppose the attacker steps forward with
his right foot and slashes at your face with
the side of his right hand (a typical attack
in Western styles of fighting and in
karate). You slide your left foot to the
rear as you parry his slash with your left
arm. The parry is meant to deflect the
slash, not to stop it or even to slow it,
since either effect would require strength
from you. During the parry you guide your
attacker’s right arm downward into the
grasp of your right hand. While still not
fighting the forward momentum of his slash,
you pull him around in the circular motion
you have begun with the withdrawal of your
left foot.
The opponent was relatively stable
against a pull directly forward because of
his extended right foot, but is highly
unstable against a pull forward and to his
left. In such a direction his center of mass
does not have to be moved far before he
becomes unstable against a fall. Therefore
as you continue to circle you pull him in
that direction. He now has two serious
disadvantages. First, he is committed to a
forward motion that would take a
considerable force to stop, even from
himself. Second, your pull and his motion
are removing his center of mass from his
base of support.
To complete the throw rotate your
attacker’s right arm downward while
stepping to your left rear. Turn his wrist
upside down and bend his hand around it. At
this point it is impossible for him to
prevent the throw. He is now off balance and
completely unable to stop his own motion. He
also cannot pull out of your grip because
you have bent his arm at the wrist. Although
his arms may be strong, he cannot prevent
the torque you create when you push his hand
around his own wrist. You bring him to the
mat.
How would a strike to the head be handled
in karate? In the Korean style of karate
known as “tae kwon do,” I was taught to
parry a slash with a powerful strike across
the opponent’s arm. Deflection was
important but so was countering the slash
with a large force. Force was working
against force, and usually the stronger
person won (I was rarely that person).
In contrast, circular motion is employed
in aikido both for deflection and to aid in
throwing an opponent off balance. Suppose
someone approaches you from behind, reaches
around your body and pins your arms to your
sides. You should reach upward and hold his
hands tightly to your chest while sliding
your foot forward.
The timing is critical because you want
to move your torso forward at a rate
matching the speed of your opponent. If you
delay, you will lose the advantage of
exploiting his momentum. If you move too
fast, you will have to drag him forward. You
must slide your right foot forward at the
correct speed and then suddenly lean forward
and rotate your body to the right.
The combination of your opponent’s
momentum and your rapid rotation throws him
off balance to the right. He cannot prevent
your throw because your lean forward brings
his center of mass forward of his feet. He
cannot release himself from the forward
motion because of his established momentum,
because you have pinned his hands and
because of his grip around your arms. The
centrifugal force on him during your rapid
rotation is too large for him to deal with
in this unstable position. Hence he
essentially throws himself to the floor.
Two more examples of how aikido employs a
small force to bring an attacker off balance
entail stick fighting (called a jo) that is
taught to more advanced students. Suppose an
attacker thrusts a long stick at your
midsection, advancing with his left leg
during the lunge and thrusting the stick
horizontally, holding it with the palms of
both hands down. It would be futile to try
to stop the end of the stick. You rapidly
step forward with your right foot so that
the stick passes you on your left. (The
agility to do this comes only with long
practice.) As the stick passes you, turn
your body to face it so that you can grab it
with both hands. Your left hand is forward
of your attacker’s outermost hand. Your
right hand is between his hands.
In grabbing the stick your objective is
not to stop its motion, which would require
considerable force. Rather it is to deflect
the lunge upward, around to your left in a
circular motion and then up and over your
attacker’s head. Once he has committed
himself to the forward lunge he can do
little to prevent the deflection. He would
need a large force to stop his momentum, and
he cannot thrust horizontally at your
midsection while pulling downward to prevent
your deflection.
Once you have the stick over your
attacker’s head he is easily thrown. With
his left foot forward he is highly unstable
against a pull to his left rear because in
that direction his center of mass must move
only a short distance before it is no longer
over his support area. When you have the
stick over his head, you pull it downward
over his back in that direction. He falls to
the mat on his back and probably releases
the stick.
Suppose you have a stick and a determined
attacker rushes forward to grab its forward
end. Allow him to grasp it, but lead him
with it (as if it were a carrot in front of
a donkey) so that he continues his rush.
Also lower your end of the stick (the end he
is grabbing) to trick him into bending
downward.
Once he has committed himself to this
awkward motion and is about to pass to your
right side you bring your end of the stick
upward over his face and then back downward
over his back. If this motion is executed
rapidly, he still has a strong grip on the
stick and therefore is bent backward by your
pull downward over his back and by the
continued forward motion of his torso. The
torque due to his own weight rotates him to
the floor around the pivot point of his
feet. His grip on the stick also provides a
torque that rotates him. He actually throws
himself to the mat because of his initial
forward thrust and a bit of trickery on your
part.
Aikido has hundreds of techniques for
employing such trickery against a determined
opponent. In nearly all of them a small
deflection of force parries an opponent’s
thrust and then guides it so that he throws
himself down. When I watch an aikido master
defend himself, the motion seems fluid and
effortless, and I am inclined to suspect the
opponent of faking when he falls to the
floor. The fall is not faked. It looks that
way because the master has spent years
developing an intuitive feeling for the
basic physics of forces, rotation and
torques. ~ By Jearl Walker
