In aikido we are always talking about relaxing and falling into our movements, but I think this can be taken too far at times and can lead to some stability problems that I'll call the jumpy jelly leg syndrome. This can lead to problems in your judo too. Let me give you some background.
In order to take a step, you stand in an upright posture with knees slightly bent and feet under you. Disengage one leg - just turn it off - and your center of mass starts falling in that direction. Then you turn the leg back on under your hips and recover the leg that you left behind so that it is under your hips too. You have taken one sliding (tsugiashi) step.
The problem comes right as the leading foot hits the ground. If you are only thinking to turn it on to keep your center vertically off the ground then your side-to-side and front-to-back muscles in your leg and hips and abs and back are left in an indeterminate state with your brain not really telling them to do anything at all. If you happen to be bumped right when the leading foot hits the ground then you can get this hyperactive reflex in these muscles that causes you to rock and bounce a few times before you can get your balance back. I'm sure you've encountered this if youve done randori with someone really good. They touch you and you either stand there bouncing spastically or you jump your own butt right out of the ground.
How to fix the jumpy jelly leg syndrome? Give these otherwise-indeterminate muscles something to do. Doesn't especially matter what - just giving them a little tonus shuts down a lot of that bounce. For instance, you can:
- Think about pulling yourself forward with the front leg just as it hits the ground. This turns on all the muscles in the back of the leg.
- Think about tightening your thighs together to snap your recovery leg back under you. This turns on the thigh adductor (groin) muscles in the front leg.
Whatever scheme you use in your mind to get your legs to do this trick, your goal is to recover your rear leg back under you as quickly as possible and make your front leg active in the process. I often tell myself during walking kata to snap the recovery leg back under my hips.
So how can you practice this? I say practice it in several different ways under different conditions. For instance...
- Concentrate on this phenomenon especially during the first three or so moves in the walking kata. When you get good at that, spread it out into the pushing moves in the walking kata and from there, apply it to the turns.
- Concentrate on this phenomenon when doing the nagenokata version of okuriashibarai. The side-to-side motion with a partner should be a great place to play with this. Have your partner bump you as the lead foot hits and see how different stepping strategies help or hurt.
- Do the foot-sweep-to-control drill with a partner walking together up and down the mat bumping and sweeping deashibarai every third step. Here uke gets to play with stepping strategies just like in the side-to-side motion, but tori also gets to concentrate on putting a little drag on the front foot right as it hits on the third step. This should make the ball of the foot drag back toward tori ever so slightly right as the foot hits.
Try it and let me know your mileage. Down with the jumpy jelly legs!