Internal Concentration

• Mental Concentration. Mental concentration is a disciplining of the mind to rid itself of all distractions and to focus on the task at hand. If the mind concentrates on a task, the body can intensify the physical force it generates.
• Physical Concentration. Have you ever tried to pull down a stuck window? You pull and pull with all you might but it will not give. Then you suddenly jerk downward and it breaks loose and comes down. You concentrated your effort, and it worked. To attain maximum power, you must learn to use all your muscles and body mass to concentrate power into a technique. Using the leg or arm muscles alone will not generate maximum power; a coordinated effort by the entire musculature of the body is required. When performing a technique, initially, all the muscles of the body are relaxed but alert. Then they must sequentially contract with maximum force against a firm base. This, along with the driving force of the body mass, concentrates maximum power at the point of impact. At the moment of impact, the entire body is under maximum tension so the reaction force of the impact is transferred through your body to the firm base and back again to the point of impact. To attain this level of coordinated body effort, you must train regularly and often.
  

External Concentration

Concentration is not only internal to the body; it also involves concentrating the internal forces of the body upon an external target. The smaller the surface area of the striking object, the greater the force per square inch is transferred to the target. Pressure = Force/Area. Therefore, the pressure applied to the target may be increased by increasing the applied force or by decreasing the area that is applying the force. A side thrust kick that strikes with the edge of the heel (small area) will hit with a much greater force than the same kick that strikes with the bottom of the heel (larger area). 

If a person stands on snow while wearing snowshoes, his or her weight is spread over a large area, and the force is not enough to penetrate the snow. If the same person stands on snow without the snowshoes, his or her weight is concentrated in a smaller area and he or she sinks into the snow. Thus, the smaller the striking area the more striking force is transferred to the target. Conversely, the smaller the target area, the less power is transferred to the target and greater damage is done to the striking object than is done to the target. For example, a strike to the opponent’s abdomen with the fist will damage the abdomen, but if the same strike hits the point of the opponent’s bent elbow, the elbow will damage the fist.