First let me be up front with the caveat that I consider myself a judo beginner. I write this not to share knowledge of judo, but to as it were chronicle the evolution of my own understanding—which may be entirely mistaken at this stage.
That said, I had an understanding of forward throws—let us take o goshi as an example. I would pull and enter, turn with bent knees, fit under my opponent, straighten my legs to get him airborne, and his footing lost, pivot—my right shoulder to my left knee—so as to rotate him about his centre of gravity, turn him onto his back, and land him on the ground. Looking at this in terms of trivial mechanics, the process would then consist of
- Kuzushi—break tori’s balance forward so that his centre of gravity lies in front of his feet.
- Tsukuri—enter with bent knees to place my centre of gravity below his.
- ???—lift him up.
- Kake—rotate and throw.
I’m not sure this is so wrong for o goshi in particular, but it’s becoming increasingly apparent to me that as a general rule, step 3 is not only unnecessary, but in fact unproductive and inefficient. My judo instructor often admonishes people not to waste energy throwing people up, when the whole point is after all to throw them down. This should be rather obvious, but I had the lesson driven home kinetically when a friendly brown belt threw me with morote seio nage, a throw I’ve had great difficulties with. Instead of the ballistic arc I’m used to flying on, I had a new experience of describing a very tight circle and hitting the ground from a smaller height but much more rapidly.
Combined with the aforementioned admonishments from the instructor, and my own focus on morote seio nage and bending my damned knees, this has provided something of an epiphany. The “lift the opponent” step above isn’t just unnecessary, it’s inefficient. Instead of raising my opponent off the ground so that he can rotate freely about his centre of gravity, I want to place my centre of gravity close to and below his and rotate him about our common centre of gravity. Because this is lower than his (mine being lower, and it being in between), this means that he goes down more directly and rapidly. Because it involves no lifting, it takes less energy on my part. And rotation about the common centre of gravity, I figure, will surely involve the least possible effort for the effect: I don’t need to shift the net mass at all.
The feeling is effectively one of performing a smaller arc, or tighter circle, during the kake phase of the throw. It’s perhaps less spectacular because the amplitude is a bit smaller, but it’s much faster and requires vastly less energy. Morote seio nage in particular feels like a different throw (one that might actually work), but ippon seio nage benefits similarly, and I expect to see progress in harai goshi and other throws, as well.