A Brief Study of the Kinesthetics of Karate – Understanding Movements of Karate Strikes
DISCOVER – Vol 21 No. 5 – May 2000
THE PHYSICS OF KARATE – Michael Felt, et al
A person’s body is the sum of all its parts. When the parts work together properly, then the whole becomes greater than the parts. A simple example is the difference in power found when punching with one arm only, or doing the same punch, and having it start at the hip, with a strong stance and also retracting the opposite arm.
A properly delivered punch reaches its maximum velocity when the arm is about 80 percent extended. A student is taught to focus the punch using imagination so that it terminates approximately two inches inside the opponent’s body, rather than on the surface. A peak velocity of 10 to 14 meters per second will produce more than 3,000 newtons. The karate student focuses his blow in a small area. Thus a large amount of momentum is exerted through a small area. The effect of the strike is intensified because the time of focus is extremely short, especially at higher levels of capability. The closer one is to the target the more force that one may create. This applies where the arm or leg reaches the target just before the peak of its travel arc. Once beyond that peak, the limb starts to lose power as potential energy starts to turn into kinetic energy. To deliver the maximum power, one must make contact before the slowdown begins. The concept of slowdown occurs after the punch reaches its optimum distance about 20 percent before full extension.
Michael Felt in his article states bone can withstand 40 times more force than concrete, a bone less than an inch in diameter can withstand a force of more than 25,000 newtons. (A Newton is about the weight of an apple.) Hands and feet can withstand even more than that, because their skin, muscles, ligaments, tendons, and cartilage absorb a great deal of impact. As a result, a well-kicked foot can absorb about 2,000 times as much force as concrete before breaking. f = m x a – – – (force = mass x acceleration)
Success of a strike also depends on more subtle forces. Because of the numerous factors in delivering an effective punch or kick, the more perfect the technique is, the more power that will be developed and delivered to the target. A punch or kick uses many parts of the body. Each demands that a stable stance is crucial. The better one’s balance the more power that will be developed. The use of the proper technique to strike the proper point of the opponent is also necessary. Generally, the larger the target, the smaller the weapon used.
SPEED + FORM = POWER