It is often said that generating impact is mainly about applying your body-weight and moving it into the technique. I personally think that this explaination is a bit simplified and that there is a bit more to it than that. So some of what I am going say here goes against conventional wisdom, so please bear with me to end before accusing me of sacrilege!
Ok, so what is the main factor that generate impact in a technique?
Firstly, bear with me through what may seem like semantics at first, but lets look at the correct terminology we should be using to describe impact if we want to look in more detail at how that impact is derived! Usually we talk about “power”. This is fine for day to day use as everybody knows what we’re talking about when we say a technique is “powerful”. However, “mechanical power” (and a punch/strike/kick uses body mechanics) refers to the rate at which work can be done. So power is an on-going thing, like fuel continually being pumped into an engine or electricity continually moving through a wire. It is therefore not a correct definition for a one-off limited event such as a single technique!
“Force” is strength or energy as an attribute of physical action or movement. For our purposes, we can take the strength or energy as being the level of impact of a physical action/movement which is a given technique. So “force” is more accurate term to apply to an individual martial arts technique.
In physics, force (F) is defined as being equal to mass (m) multiplied by acceleration (a). Hence:
F = m * a
First of all, “mass” and “weight” are different, though we often use them as interchangeable. The mass of an object is a measurement of the amount of matter in that object. Mass (the amount of matter) is the same whether we’re on Earth, on the Moon or in space.
However, weight is a function of gravity being applied to mass. So our weight will be more on Earth than it is on the Moon and will be zero when in space where this is no gravity, hence weightlessness!
We tend to use these terms interchangeably as we don’t actually leave planet Earth and both our mass and our weight remain constant.
In physics the Force Of Gravity = F(Grav) is equal to the mass (m) multiplied by acceleration due to gravity (g). Hence:-
F(Grav) = m * g
The acceleration of gravity (g) on Earth is a constant. It’s 9.8 meter per second per second (9.8 m/s2). The acceleration due to gravity would obviously be smaller on the Moon and zero in space. So in both formulas, we’re looking at applying acceleration to a given mass in order to create Force!
Well there’s not too much we can do about our mass, yet acceleration is something we can easily work on and improve!
Acceleration is increasing velocity (speed). Most people think in terms of velocity only, but if we can hit somebody at a point where the velocity of the striking body part (hand/foot/etc) is actually increasing, it will have more force than hitting somebody with a constant velocity!
So how do we generate acceleration?
I was lucky enough to be taught right from the start of my training, that it’s not about moving all the body at once, it’s about moving body parts in the correct sequence. So lets look at a basic Karate/Tae Kwon Do/Tang Soo Do reverse punch.
Now this will be a simplified description, but you’ll get the gist. As we start the punch, we move the hip first so we have the velocity (V) of the hip = V(hip).
As the hip comes close to completing its rotation we initiate the shoulder so we add the velocity of the shoulder = V(shoulder).
We now have V(hip) + V(shoulder).
Then we release the hand and add it’s velocity to the punch = V(hand).
We now have V(hip) + V(shoulder) + V(hand).
(There’s a bit more to it than just that, but this will do for this demonstration)!
So rather than having a constant velocity, you can an increasing velocity throughout the technique, which is acceleration!
To do this properly you need a whip-like technique which some people have trouble doing due to too much tension in their body. If you are not sure how to actually do this, then please see my earlier posting on How To Put The “Whip” Into A Linear Technique.
Now, going back to the notion of using body weight to generate impact. As we’ve seen above, weight (in the how much do I weigh sense of the word) is created by mass acted upon by gravity; and the Force of gravity is always resultant on acceleration (g). So to apply body weight forward in a strike/punch, we need acceleration applied to our mass (mass being constant, weight being resultant from applying acceleration to that mass). So increasing the acceleration through good technique (moving body in sequence) increases the effective body weight striking the target, (even though the mass remains the same).
If we move all of our body parts at once, rather than in sequence (bad technique), we still move just as much body mass, but we don’t generate the same acceleration, hence less effective body weight and the impact is significantly lower.
Some people with bad technique will try to be fast by just shooting out their arm without using the rest of the body behind it. Firstly they only use a small part of the body mass, so that will limit the force of impact. Secondly, not activating the body in sequence will not give much acceleration, (hence not much body weight) so again the force of impact will be limited.
Lets look at other ways to apply this. Whereas say a reverse punch from Karate/TKD/TSD, etc typically rotate the hips about 45 degrees to generate forward inertia; many systems of Kung Fu typically use centrifugal force and rotate their hips almost 180 degrees. If you look at the video below of a Kung Fu Punch, although the punch goes out straight, most of the body mass does not move towards the target. It has less forward inertia or body mass than a Karate/TKD/TSD punch, but more centrifugal force and is still powerful.
In the next video we see a more circular strike (Sao Choy), but still the body mass is not really moving towards the target, it is rotating rapidly to generate centrifugal force (like the video above). There is some movement of body mass at the end of the movement, but if you look closely you’ll see that it is moving parallel to the strike and is not actually behind it.
In both of these videos as the body rotates, the side of the body nearest to the striking arm moves closer to or parallel to the target whilst the other hip moves further away. This, on the surface, contradicts conventional Karate/TKD/TSD wisdom of moving the body towards the target! Yet if you have ever trained in Kung Fu styles like these (or with somebody that does these styles of Kung Fu) you will know that this type of strike can be very powerful indeed despite not moving much body mass towards the target! But it still follows the same same sequence of:-
V(hip) + V(shoulder)
V(hip) + V(shoulder) + V(hand)
In other words, the striking hand is accelerating throughout the technique thus increasing the force of the impact (F = m*a). It uses less body mass moving towards the target (some body mass is moving away) then the Karate/TKD/TSD version, but the acceleration is greater.
Here’s another video by Russell Stutely who I’ve had the privilege to train with, talking about “heavy hands”. He generates a seemingly ridiculous amount of impact with hardly any effort at all.
You’ll notice that his main way of demonstrating this is to simply drop the hand and let gravity take over.
Russell is not actually applying very much body mass at all (though it feels very heavy to his assistant) and very little of his body mass actually moves towards his target, yet the effect is dramatic. He is using the acceleration due to gravity of his dropping hand to create that “heavy” feeling creating significant body weight despite using very little mass (just his arm). And having trained with Russell and been demonstrated on by him, I can personally assure you that what he does is real.
Now to get any significant acceleration, we need a high degree of relaxation. You can’t accelerate a tense a body (or at least, not very efficiently). And so we go back to what we’ve always been told from the beginning (or should have been) and that is to relax. And this is why little old masters seem to generate enormous amounts of impact with hardly any effort at all; it’s because they have achieved a high degree of relaxation which allows them to apply high acceleration to their body mass which in turn creates the force of impact.
So to summarise:-
- Force is actually a better term than power to describe impact as it relates to a one-off event (such as a given technique).
- The force of the impact is partly to do with our body mass, (though we can’t do too much to change/increase it).
- Force is also partly about acceleration which we can do a lot about to control and increase.
- By moving our body parts in sequence rather than altogether, the striking body part is accelerating (NOT moving at constant speed).
- Weight is a result of gravity applied to our body mass. Gravity requires acceleration. So moving body weight forward effectively requires acceleration applied to our body mass.
- Acceleration can only be effectively achieved with a high degree of relaxation, which is why some people can generate enormous amounts of impact with seemingly very little effort.
Although some of this goes against conventional wisdom I hope this has been insightful and useful for you. If it has, please comment below and share with your friends.