of your blow. This is why a strong stance is needed and explains the advantage of using follow through motions rather than stopping on impact, because the reaction force is completely nullified by the continuing momentum of the technique.
The law of reaction is applied in many different ways, as, for example in the use of antagonistic muscles. It is well known that the contraction of the biceps will produce an extension of the triceps (these muscles are called antagonistic muscles). This property can be turned to account in karatedo. Before kicking, the heel is raised backward, almost to the buttock, extending the fore-muscles of the thigh. When the heel is thrown forward, not only are these muscles strongly contracted, but the foot describes a longer trajectory and in doing so, gathers more momentum.
The reaction principle is also utilized in push-pull types of motion. If you are punching with your right fist, pull your left fist back to the side of your left hip. When kicking, pull your hands back to your waist or downward on each side of your body. In fact, a technique is not completed until after the blow has been pulled back. The punch or the kick has to be executed and retracted at the same speed and in a single continuous motion to take full advantage of the action reaction principle.
Inner power
This is perhaps the most important single source of power of the human body and also the most difficult to generate because it requires the coordination of physical as well as physiological principles. Physically, the inner power is the result of the force of the abdominal muscles located below the diaphragm. They are the strongest muscles of the body and take a prominent part in the transmission of force as they link the upper and lower body. When the abdominal muscles are contracted, the whole body becomes one single mass concentrated around its center of gravity; thus, in momentum MxV transmitted to the striking extremity, M represents the total weight of the body. Abdominal muscles must thus be contracted right at the beginning of the motion to solidify the body into one mass, on which, step by step, other muscles are going to rest to transmit the striking force.
The force of the abdominal region is developed by correct breathing and use of the centripetal pressure of the abdominal muscles. The proper way to breathe is to inhale deeply from the nose, lifting the diaphragm and filling up the lower abdomen (tanden) with air. The breath should then be held in the tanden and the abdominal muscles should contract to create an antagonistic pressure called centripetal pressure. This is truly the source of inner power. The lower abdomen should always remain slightly tensed, filled with ki, in a position of equilibrium between the centrifugal force excited by the breathing and the centripetal pressure of the abdominal muscles. This kind of respiration provides a constant massage of the internal organs (liver, spleen, and stomach) and facilitates blood circulation by pushing back to the heart like a pump, the blood irrigating the lower part of the abdomen. The movement of the diaphragm relaxes the solar plexus which is an important nervous center, and as a result, the functions of the central nervous system are better controlled and the mind becomes more serene.
Another effect of abdominal respiration is the lowering of the center of gravity. In normal respiration, the chest is inflated and the shoulders are lifted, thus the center of gravity moves up. Breathing with the lower part of the diaphragm creates a centripetal pressure by which the internal organs are pushed downward and the center of gravity is lowered considerably, thereby increasing the stability of the body.
Distance, timing, and speed
These three factors are lightly correlated and are extremely important for the transmission of a maximum force to the point of impact.
Distance refers, in this paragraph, to the length of segment joining the striking part and the target. Your reach is important for this particular technique. If this distance is too long, the force of the blow will be wasted. You may lose your balance and the opponent will have a chance to counterattack. If the distance is too short, the striking part will not have attained its maximum speed. Therefore its momentum will be small and the blow will be ineffective. Furthermore, if you are too close, the opponent will have a chance to hit you before you strike. The reach is usually the full length of the arm or leg, and is developed by practice with the makiwara (a board used for punching, kicking, and striking practice).
But in karatedo, the two opponents usually do not stand within reach but rather just over one step out of reach. Therefore, to deliver a blow one has to close the gap and bring the opponent within his own reach. Body movement to close the gap provides additional momentum, usually a linear momentum. The feeling for the right distance is developed through assiduous practice of pre-arranged kumite and shiai. The proper distance, called maai, depends on a number of factors, such as your own stance, the technique used, physical characteristics (size and speed), and those of your opponent. If he is moving, the direction and speed of his move have to be taken into account. It is like shooting a bird; you do not actually shoot at the bird, but at some point ahead on its trajectory.
If the opponent stands too close for you to properly execute your technique, you can either push him backward or step back or sideways to create enough distance. You can also change your technique, using elbow or knee techniques more appropriate for close fighting.
Timing refers to the propitious moment for the execution of a technique. It is the moment when your concentration of force is at its maximum and the opponent presents an opening in his guard at the right distance. Timing is thus the precise coordination of your own action with the opponent's attitude. Such opportunities occur when:
a) your opponent is just about to attack: at this time he is usually too preoccupied by his own attack to think about his defense. It is the most favorable time because in this case you win without actually fighting.
b) your opponent has just finished his attack and is about to withdraw: his energy has reached its peak and he cannot mount any resistance to your action.
c) your opponent is moving backward after an attack or away from you; he cannot offer any resistance because your energy goes in the direction of his movement.
d) your opponent is blocking your first technique; he is then open to the following one.
e) your opponent stops his motion or loses his concentration; there is a disruption in the flow of his energy
f) your opponent is exhaling or has just finished exhaling;he is losing his ki and his energy is at its lowest point.
g) your opponent is off balance, or changing stances, or shielding his eyes; he is then open to an attack.
Proper timing can only be achieved by intensive training in kumite and shiai.
Speed is important not only in reducing the risk of a counter-attack by an opponent during the execution of a technique, but also because speed is transformed into power. The kinetic energy of a mass M moving with a velocity V is proportional to the product of this mass by the square of its velocity. Thus the kinetic energy of a mass moving at 10 meters per second is 100 times greater than the energy of the same mass moving at 1 meter per second. This clearly shows the advantage of executing a technique with speed.
Speed is produced by muscular action. The coordination of the proper muscles can be improved by repetition, eliminating the contraction of antagonistic and unnecessary muscles.
An example will help illustrate how these different physical principles are utilized in the execution of punching and kicking techniques.
For an offensive technique, the preparation phase will consist of a forward body motion (using neko ashi or fumikomi ashi ), which generates a linear momentum used in the execution phase described below.
Hineri
