Power Generation by Mark Kupsz
A lot of people confuse the terms force and power. A force is a push, pull or twist. Power on the other hand is how quickly a force is applied i.e force / time. In karate for the majority of instances force equates to the ‘hit’. The basic principle behind generating a force is F = M x A. (mass x acceleration). If you consider that at any one instance your mass is fixed then the greatest factor influencing the amount of force created is how quickly you can accelerate a technique. That is not to say that mass should not be considered as an important factor. Here I elude to the fact that you have to get body mass behind a technique and this is a point that students often fail to comprehend fully. I am forever telling my students to try first to hit with the body then add on the acceleration of the limbs. Hitting with the body can only be achieved whilst the body is still in motion. Once you have planted your stance you are no longer in motion so you have decelerated your body mass. Despite the fact that your limbs may still be in motion you have robbed the technique of momentum. In karate we work hard to develop body momentum so do not undo this by applying the brakes too soon.
If you allow yourself to ‘fall’ into a technique the maximum acceleration you can expect to achieve is that due to gravity, approx 10m/sec and even this takes some time to achieve depending on the amount of inertia you need to overcome. Stepping is a kind of ‘slow motion’ freefall. When we step we alter our centre of balance and place our leg out to prevent ourselves falling over completely. To generate greater acceleration we have to add an additional force to that of gravity i.e. a pushing force.
You can understand this if you consider a bullet dropping on you from above compared to one that is fired from a gun. The mass is identical but the acceleration is far greater when fired from a gun, hence more destructive force. A common misbelief is that a coin dropped from a skyscraper would kill a person if it hit them below. This is not the case as the coin reaches a maximum velocity after about 10m and does not keep accelerating throughout its fall due to air resistance and so it wouldn’t hurt any more than a coin dropped from a height of 10m, which is not enough to do any harm. This misnomer was demonstrated on the program ‘Myth Busters’. Anyhow I digress from my main point. To gain initial acceleration of the body you have to create an initial strong push to overcome the inertia of your body at rest. No person can go from zero acceleration to their maximum instantaneously it takes time to accelerate; for example sports cars take about 3.5 seconds to go from 0 – 60mph. During this time there is a constant push from the engine which via the transmission and the wheels accelerate the vehicle forwards.
If you apply this concept to a technique like gedan-barai the initial focus for the move should be a preparation to push. I achieve this by dropping my centre so that my rear leg bends to the limit of my ankle’s flexibility. I then try to concentrate on pushing very hard against the floor with my rear leg to generate as much forward push as I can. It is important at this point to ensure that the hips travel in a straight line forwards and do not rise or else some of this pushing force is directed upwards and does not contribute towards increasing your forward momentum. This forward push is transmitted to the front leg so that it bends past 90-degrees. Once my hips are past my vertical axis and my body centre starts to move over my front leg I switch to pushing with that leg. The key to maximising acceleration is how smoothly you can go from back leg push to front leg push. In other words you must try to keep the continuity of the pushing force. This takes diligent practice. Once you have your body in motion you move on to what can be described as the ‘float’ stage of the technique. This is a period of total relaxation. Any muscle tension in the later part of the acceleration tends to inhibit speed rather than enhance it. The aim is to try and realize maximum acceleration for your particular body mass. Lighter people will achieve this more quickly as there is less inertia to overcome. If you hit the target at the point of maximum acceleration you have achieved your potential largest force. However transmission of this force is another key factor. This is the point at which you need to regain muscle tension to maximise the locking up of the body…i.e. the point at which you kime. I can see merit for applying the kime instantaneously with the hit and also for applying it a fraction after. If it was a solid object that was being struck then maybe I would say instantaneously but because we are hitting flesh, a surface that initially compresses I think it might be better to allow some penetration before the kime is applied. It’s probably better to experiment with a bag and try to get a feel for both methods.
If I might add that the body acceleration and the arm/leg acceleration are two separate components of the attack. You should aim for maximum on both. You then get a summative effect. Similar principles apply to maximizing arm speed. You need a strong initial push. The key to this is using the correct arm muscles at the correct time. It is both fortunate and unfortunate that muscles work antagonistically (i.e. both push and pull at the same instance) You have to isolate the main push muscles and try to ‘switch off’ the other muscles that are trying to pull back on the motion. Relaxation is the key to achieving this.
Finally back to the original point. All of the above is central to generating a strong force. Power is about how quickly you can deliver this force. If you are moving at maximum speed already then power should also be at maximum. At this point I try to think of ‘shocking’ my opponents body i.e. very rapid deployment of technique. BANG! in and out a bit like an explosion going off rather than focussing on following through with the technique. Sorry if this last part is a bit esoteric but it is hard to explain all aspects of technique using scientific explanation and sometimes it helps understanding if you discuss it in terms of the feel of the technique.
