A definition for the centre of mass of an object is; a point representing the mean position of the matter in an object.
In other words, if you were to start pushing on something at the point of its centre of mass you will encounter the greatest resistance. Or if something pushes on you concentrated through its centre of mass, you will have the hardest time resisting.
When you see a picture of where the centre of mass is for different objects, it makes more sense; except perhaps for the ‘donut’ shape.
When you see where the centre of mass is on the human body you will also see that this is the same place as the area we learn and know as our dan-jun.
In Hapkido we are instructed that on the human body the dan-jun is approximately the measure of 3 fingers below and 3 fingers in from our belly-button.
There is much more to ‘dan-jun’ in Hapkido other than it being a person’s centre of mass. However a person’s centre of mass is located where we locate our dan-jun and this is important to know.
We are told to train with awareness of using our ‘dan-jun energy’ when delivering our techniques.
We aim to do this among other reasons to use as much of our mass as possible, rather than relying on the strength of some of our muscles alone.
Why try to use dan-jun?
One reason we use dan-jun is because we can deliver much more force in a technique if we use our dan-jun. This is not just a Hapkido principle but it is also a basic law of physics. Force is equal to mass multiplied by acceleration.
[Force = Mass x Acceleration]
So the more mass and acceleration that we can put into our actions the more force we can generate.
If you want a more forceful technique, whether that is a punch, kick or Kibon Su etc. put your dan-jun into it!