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The most effective application of the body mechanism naturally is governed by the dynamic law or the principles of leverage and balance. For convenience, I will dissect and tabulate here the general principles that apply to judo.

• Balance.
I have already described the general conditions how to keep the balance of the body. [See "Twelve Judo Throws and Tsukuri," at http://ejmas.com/jcs/jcsart_koizumi_0302.htm.] However, in applying a throw, you have to risk weakening the balance and stand on one leg, so that you can free one side of your body which is chiefly used in performing the act of throwing. This stance may vary according to the nature of the action, but in the main it consists of bending the ankle and knee so as to increase the "base" and lower the centre of gravity. Then the balance is retained, through the changing conditions in the stages of action, by subtle co-ordination of the ankle, knee and hip joints.
• Unity of Action.
The side of the body freed for action should be used as a solid lever. Merely stiffening the joints is not sufficient; there must be co-ordination of all muscles. This co-ordination is more possible if your mind is concentrated on the abdominal action. When your mind is occupied with the action of the hands or feet the lever will disintegrate; so will the effectiveness of it.
• Abdominal Power.
The abdomen does not assume any importance in the Western conception of physical education, but in the East it is regarded as the centre and basis of all physical and spiritual power. Indeed, in judo abdominal power is the foundation of all actions and movements. Therefore to cultivate fullness at the abdomen (not strained contraction nor enlargement) and firmness of the small of the back is a very important item in judo training.
• The Body-Lever.
As our common experience demonstrates, the most effective way of using a lever or stick to pull or push an object is to use it lengthwise. However, the contact and stance of our body related to the opponent is such that the only way to conform to the above principle is to curve our body from the finger tips to the toes and use the body-lever in the line of that curve. This applies to the local use of arms, wrists or fingers. Another way of using the body-lever is as if it were connected to the hip joint of the leg on which you are standing with a swivelling hinge.
• Two Wheels.
If you assume that you have made a contact with your opponent in the usual manner and you have adopted the curved posture, you will find that you have formed with the opponent roughly two rings or wheels: one with the arms, another with the two bodies. To follow the principle of using the body-lever as described above, the way is to move the wheels as if they were rotated on an axis. According to the purpose of the action the angle of the axis may change, but the forms of the wheels must be retained from the beginning of the action to the end of a throw.

These technical principles are the basis of and the vital factors in the efficiency of judo. The skill depends on the ability to operate them in the right direction at the correct moment.

To incorporate these principles into a single action in a psychological moment is beyond mental control. Therefore through constant practice the body must be trained to act automatically. In general practice the sporting instinct certainly must be satisfied, but the study of theory must not be neglected.

If in your effort you find your shoulders move upward the shape of the wheels changes and the balance is weak, the opponent's arms or body are in your way (assuming he is passive), and you should take this as the sign of wrong movement.

There is no dogma with judo. Therefore a method cannot be said to be wrong or right, but by testing it against the maxim "maximum efficiency and minimum effort" it can be said that one is better than the other. Thus judo is progressive and each one of us is a potential contributor towards its further development. No one is perfect; all are fellow pilgrims to unknown possibilities.