Judo Works for Everyone: The Physics of Throwing People
Ron Then
Audience and Scope This work document will introduce and describe Judo and how its practitioners utilize basic, physical principles to execute throws efficiently. The target audience is those who may be considering a martial art for fun, exercise, or self-defense, and this document hopes to inform and sway those people toward Judo. Some basic physical principles will be described, followed by examples of throws to emphasize how physics is involved in Judo. Everyone can benefit from Judo!
What Judo Is: An Introduction
Judo is a sport, a martial art
and a fun way to exercise and enrich one's life. Unlike other martial arts, Judo primarily utilizes throwing techniques, rather than strikes, allowing practitioners to fully resist and attack their opponent. Judo is best known for its spectacular throwing techniques and ground fighting, but many are not aware of the fact that the emphasis of technique and timing over brute strength allows people of all sizes, ages, and athletic abilities to train and benefit from Judo.
Professor Jigoro Kano developed Judo around 1880; He sought to create a modern version of samurai martial arts that would remove the dangerous aspects, allow participants to safely learn and exercise, and popularize the martial arts in an age that saw the decline of traditional ways of Japanese culture.
Judo utilizes basic principles of physics to maximize efficiency when throwing an opponent. For this reason, a smaller player will be able to throw a much larger opponent with little effort when the timing and technique are correct. As a result, anybody can practice Judo, old or young, strong or weak, and have an enjoyable, enriching experience.
Physics at Work
Many of us have some intuition about basic
physical principles such as force, torque, inertia, and momentum, even if we have never formally learned physics. For example, when one is walking and finds they are falling after kicking the curb, it is due to a torque being applied about the foot by the continued forward motion of the upper body. It is not hard to imagine how the physics of falling over a curb is analogous to the physics involved with a typical leg or hip throw in Judo.
Momentum is defined by Sir Isaac Newton as mass times velocity. This means that a larger person moving quickly has a lot of momentum; when they kick the curb and their foot abruptly stops, they have more momentum to try to stop before hitting the ground. The same thing applies to Judo.
Kuzushi: Destroying the Balance
The idea of taking your opponent off balance is referred to as Kuzushi in Japanese martial arts. Imagining your opponent as a block, the block can be tipped in different directions: forward, backward, side-to-side, diagonally. If your opponent is standing straight up, it will require a lot more strength to through them than if you take away their balance and then use physics to throw them.
The block on the right represents your opponent.
Gravity points directly down to earth, in the middle of the block: when the opponent is tipped, the top half of them is technically falling. Stopping their foot or hip while their upper body is falling forward creates a torque, allowing one to throw their opponent over them quite easily.
The Throws: Utilizing Momentum and Gravity
Sasae Tsurikomi Ashi
The throw pictured above, Sasae Tsurikomi Ashi, is a powerful leg throw that is analogous to tripping over a curb. The thrower pulls his opponent forward, destroying his balance, and then stops the opponents foot with his own (as if it were a curb), causing the person to fall. The red arrow in the middle frame describes the force of gravity acting on the person’s center of mass. By stopping the foot, the thrower prevents the opponent from regaining his balance, and causes a torque at the foot. The larger or taller the person being thrown is, the larger the torque, causing the person to fall with much more force.
Tsurikomi Goshi
This is a hip throw called Tsurikomi Goshi. The same principles are involved as with the previous throw, but this time the thrower is using his hips as the pivot point instead of the foot. By getting his or her hips underneath the opponent’s center of mass, and using the same principle of Kuzushi to cause the opponent to be off-balanced, the thrower causes his opponent to fall over his hips. A very small player can throw a very large player with this throw.
Judo for Self Defense
Judo is a great martial art to learn for self defense because it emphasizes the use of technique, timing, and physics to execute throws instead of brute force and striking. Why is this so beneficial? In a striking based martial art, it is not possibleineffective to punch your training partner as hard as you canwith extreme force to master a technique. Due to this, practice must be conducted in a slower manner, which is not conducive to real world situations.
When Judo is practiced on proper mats, practitioners can throw each other as hard as possible and not injure their opponent. This allows those training in Judo to experience a fully resisting opponent, which lends itself to real world situations and also provides a better physical conditioning environment. Another benefit is that smaller people can learn how to defend themselves from large attackers, as shown in the picture to the right, where a small child is throwing a fully grown man.
Concluding Remarks
Judo is a wonderful, exciting way to get in shape, learn self-defense, and enrich your life.
Training in Judo can help practitioners:
· Increase their level of physical conditioning and athleticism
· Learn to defend themselves against opponents of all sizes through the utilization of physical principles against fully resisting training partners
· Have fun practicing a martial art in a safe environment
· Release stress
In conclusion, by using physics, timing, and technique as demonstrated by the above examples of throws, anyone can practice and appreciate the beauty and physical benefits of Judo.
Sources:
Judo Unleashed, Neil Ohlenkamp
judoinfo.com for pictures
Kodokan Judo, Jigoro Kano