a short note on centres

or: revealed! the purpose of knee lifting

your centre of mass is the point at which you would balance in any direction. it is, essentially, 'the middle' of you; sometimes this is referred to in martial arts simply as 'the centre', and can take on a spiritual meaning for the purposes of reflection and meditation. in a practical sense, though, the centre of mass has a specific utility: if you push through the centre of mass of an object, the object will move. push anywhere else, the object will rotate. for karate, techniques delivered through the centre of your opponent will move them, rather than an off-centre centre technique which will lead to either a rotation and/or deflection. targeting to the centre also tends to give a solid orthogonal-to-surface impact, and minimises the possibility of scuffing off the target.

consider the 'standard' four kicks of the shotokan dan-grade syllabus: mae-geri, yoko-geri kekomi, mawashi-geri, and ushiro-geri. all of these can be delivered to multiple targets, of course, and the head remains high value, but hitting through the opponent's centre of mass is the way to maximise the power delivery of the technique. also important is the trajectory of the technique, and similarly if the kick comes from your own centre of mass the connection will be the most complete. when striking chudan, consider the locus of the foot and work to approximate the line between your centre of mass, and your opponent's. this is the source of the need to lift the knee in preparation. in the following pictures, see how the foot is raised close to the centre of mass (the red dot) before extending the kick. the line of the kick (yellow line) is therefore approximately - or as close as possible - the line connecting centres of mass (red line). for mawashi geri, the trajectory is not a straight line but the force is still delivered through the centre mass of the opponent, and originates with the foot from close to your own. a poorly prepared kick leaves the foot away from this line, resulting in a less effective kick (blue line).

in the set of images below, see that the completed kick (top picture) connects the centres of mass, and that the correct trajectory (middle picture, yellow) most closely matches this line by preparation of the foot by lifting the knee. a poor preparation (bottom picture, blue) gives a locus that does not allow for efficient transfer of power, even if the path is clear.

mae-geri :: yoko-geri kekomi

mawashi geri :: ushiro geri

if you consider not only the target of your kicks, but also their starting point, the importance of lifting the knee is obvious. it puts the foot as close to your centre of mass as possible, which is desirable for power transference regardless of where you are kicking. although not illustrated here, the idea applies equally to other kicks such as yoko-keage, ura-mawashi, ushiro-mawashi, gyaku-mawashi, and miku-zuki geri. you may also like to consider the positioning of hikite in preparation of punches, and the corollary as to how blocks intersect the line of attacks at shallow angles in order to deflect them. more on that another time.

-neil jerome, 2013

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