This year we are discussing the Book of Martial Power (BOMP)
In Chapter 25, Pearlman discusses the positioning and use of our long, vertical axis - the line that runs through the crown of our head and our center of mass (and usually, through one foot). This line represents our center of full-body rotation. Pearlman gives several good examples of how to position and control our axis - most of which boils down to...
- vertical axis (upright posture) promotes easier, faster, cleaner rotation
- smaller footwork creates a narrower axis, which promotes faster and easier rotation.
I agree 100% with this as a general case, but wanted (just for argument's sake) to discuss some counter-examples...
Pearlman seems to be saying that faster is better... "As martial artists, we need to exercise the smallest Axis possible... [because this is faster]". Well, it turns out that faster is not always better - we see this in judo and aikido especially. It is often important to be able to move at uke's speed instead of your own arbitrary (faster) speed. One of my instructors once phrased this as, "It's not so much how fast you go that matters. It is when you arrive that matters." Timing trumps speed.
But, with that said, It is still a good idea to narrow your axis through relaxed upright posture and narrow footwork, because this potential increase in speed actually allows you to slow down and relax and process as you wait for uke to arrive at the timing window. My students will probably see kosotogari as the ultimate example of this idea. I stress narrow, fast, efficient footwork so much that kosotogari often feels like a "lazy throw" - that is, tori has to wait, and wait, and wait some more before he can pull the trigger and dump uke. Tori's footwork becomes so fast and efficient that he feels like he has to lounge around waiting for uke to get to the place where he can be thrown.
Another interesting point that came to mind reading this chapter, is when Pearlman discusses keeping ones mass centered around the Axis in order to avoid wobble in the rotation. Again, I agree with this in general cases, but there are instances where that wobble can be useful. The two examples that pop immediately into my mind are kataotoshi and koshiguruma. Both of these throws happen by placing a foot (the bottom of the axis) near uke, attaching the same arm to uke, and spinning the opposite leg around the axis.
The uncentered mass of the leg creaets a flywheel-like effect, transferring power to the arm that is hooked to uke. You can sort of see this idea in Pearlman's illustrations labelled Ax13a and Ax13b. The oval shape of the uncentered rotating mass can act as a cam (see the excellent animation at Wikipedia) to impart linear motion to uke.
Again, my counterexamples do not damage Pearlman's excellent discussion of the principle of properly managing your long axis of rotation through upright posture and narrow footwork. Just interesting ideas that cropped up.