Seeing that I've been writing a series on differences between similar judo throws, one of my students asked me to clarify the difference between ashiguruma and oguruma. "Oh no!" I thought! "He's asked me the toughest one of all!" This is a pair of techniques that I've traditionally taken the easy (and incorrect) way out of by saying that oguruma was just ashiguruma at the waist.
But, that is obviously incorrect because the old dead judo guys that made this stuff up absolutely did not do this sort of needless multiplication of techniques. In the same way that taiotoshi with a sleeve-lapel grip is still the same technique as taiotoshi with a 2-handed cross grip... If they had been into multiplication of technique, then ashiguruma at uke's ankle would be a different thing from ashiguruma at uke's shin, and both of those would have been a different thing from ashiguruma at the knee and so on...
Thanks for exposing my long-standing cop-out!
So, I had to go to Daigo's Kodokan Throwing Techniques book to find an answer. It turns out that, according to Daigo these two things are pretty distinct.
- Daigo says in ashiguruma tori's blocking leg only touches uke's lower leg - no other part of tori's leg touches uke's body. In oguruma, however, tori's thigh as well as his knee or calf is in contact with both of uke's thighs.
- This means that oguruma must be done more in-line with uke's feet while ashiguruma can be done somewhat looser (though I always try to get ashiguruma inline with uke's feet too).
- Daigo also discusses why Mifune invented oguruma (see, I didn't know that either). He says that Mifune specifically intended oguruma to be used against much taller opponents, implying that the height of uke's center of gravity is the deciding factor. Oguruma is easier with a taller opponent, but it's hard to get in under a shorter opponent with oguruma so you would use ashiguruma.
- The fulcrum for oguruma really is the blocking leg, whereas (just like in hizaguruma) the blocking leg on ashiguruma is not a fulcrum - it is a foot-stop.
I guess I just learnt a thing or two. That's just one more thing to add to my already-long list of stuff to drill and practice more. I can already tell that I am going to regret teaching this to some of my smaller brown belts...