There is this classic demonstration of offbalance in Judo called Happo no Kuzushi (8 forms of unbalancing). The way it works is this. You get an uke who agrees to stand still and you push and pull him into various positions of unbalance. First you pull him forward onto his toes. Then you push him back onto his heels. then tilt him left, then right, and into each corner. Most instructors pay lip service to the happo no kuzushi and the students never see it again. Really, after seeing it once or twice and doing it once or twice there's not much to it. The main problem is uke standing still. That is totally unreal and abstract form. Uke always moves.
The theory is that you can learn the offbalances on a static partner then hope to catch someone unsuspecting in randori so that they stand still long enough to do one. That almost never works and it takes forever for people to feel comfortable doing throws in randori that way.
Here are three modifications that we're playing with to turn happo into an honestly useful piece of kihon, worthy of at least a little bit of time in each class.
- First, let uke move. Take your standard grip in shizentai. Apply one of the pulls or pushes to uke, who allows tori to move them slowly to the point of no return. This is the point whhere uke has to either step or fall. At this point, uke collapses one leg (whichever feels right), shifts, and turns it back on right under his hips. This way, uke is learning to shift using tsugiashi in response to an impetus but without having to predict how tori will apply force and leading tori.
- Second, tori moves with uke. As uke responds to the push or pull, tori matches his step using tsugiashi. Tori is learning to synchronize with uke and move with uke's force. Tori should make his foot land at the same time as uke's foot.
- Third, at the instant the feet hit the ground, tori applies a very light push or pull precisely parallel to uke's feet or perpendicular to his feet. This is the kuzushi that we're really exploring in this exercise - the perpendicular and parallel offbalances that happen right as uke's foot hits the ground.
All the throws in Judo can be done with these two offbalances (perpendicular and parallel) and it is better by far to learn to apply these two offbalances with appropriate timing to a moving opponent than to learn eight offbalances on a mannequin.