The large abdominal muscles are twisted to provide additional body momentum. Another way of increasing body weight is the utilization of a springing action of the knee joint. This is achieved by slightly raising the hip at the beginning of the motion and lowering the hip at the moment of impact to drop the body weight into the motion. In summarizing, it is necessary to point out that the principles of force outlined here hold just as true today in our modern scientific and nuclear age as they did centuries ago. I am sure that when you go through this art, both in theory and in practice, you will find that the scientific basis of the motions and the real power which comes out a small human body cannot fail to impress you.
Speed is the most essential factor of force or power.
According to the theory of kinetic energy, every object increases its weight as well as speed in a downward movement. This very principle is applied to this particular art of self-defense. For this reason, at the moment of impact, the position of the hand normally becomes lower than the shoulder and the foot lower than the hip while the body is in the air. Reaction force, breath, control, equilibrium, concentration, and relaxation of the muscles cannot be ignored. However, these are the factors that contribute to the speed and all these factors, together with flexible and rhythmic movements, must be well coordinated to produce the maximum power in Taekwon-Do.