I've a technical query regarding an aspect of koshi guruma- specifically, the function of the arm around uke's neck- on which multiple knowledgeable people who I've asked in person have given distinctly different opinions and teach in correspondingly different ways, and so have come here looking for more information.
Essentially, either- a) the arm should lock closely around uke's neck, with the shoulder, upper- and forearm applying pressure in a manner very like a neck lock, but technically not a complete one and so it is therefore legal, gives tori significantly more control of uke and increases effectiveness and efficiency of the throw as compared to b) tori's arm should not lock around uke's neck in this manner because it does in fact put sufficient pressure on the neck to qualify as a neck lock or crank, and thus has safety ramifications and if used in competition may get tori penalised; adequate control can still be achieved without difficulty by keeping the arm firm with the hand near uke's shoulder, and this is technically more correct in Judo.
A minor confusion perhaps, but it seems mechanically and competition-legally significant, and therefore worth asking about.
Opinions, explanations or otherwise additional information would be much appreciated.
If you look for black and white answers in judo you will chase your tail to the end of time. Judo is a physical human endeavour that should be tailored to each individuals body and even psychological type or character.. There are, of course, what we call 'the gokyo', The canon
of judo waza.
Even within this canon
it is not about dotting punctuation that always counts BUT are the principles of that specific throw being practiced and fulfilled.
Koshi guruma. Lets explore together. A key to how this throw is performed is presented in its name, its a kuruma waza, all kuruma waza have a distinct action, a distinct principle if you like.
Hell to write on yet so easy to demonstrate, however press on. The hip area or hara is the area that generates the power for kuruma waza and indeed is generally the focal point of the throws as it becomes the axes
that the wheel is then attached to. Ones feet and hands are the circumference of the wheel.
In terms of koshi guruma we need to achieve uke wheeling over our hips. To this end the hand position and amount of work performed by the hands is important. Take your right hand to the top back of the neck of uke, don't stretch nor straighten your Right arm if you will be either arm locked or uke will turn in under your arm and use your position against you. Hold the back of ukes, gi thumb inside, with your hand relaxed and Right elbow relaxed prepared to repel any attack uke may make.
What you, as tori, need to achieve is 'control of uke head'
This means your hands are forming that outer circle of the wheel, the kuruma.
When you turn in for ogoshi your feet are more or less directly facing the same direction as Uke feet and you bend at the knees and blah blah blah. In koshi guruma there is little if any 'lift' (height will determine this) its a wheeling action made by the action of your hip placement and use of your right hand to wheel uke around-over your hips.
In Ogoshi ones hips remain squarely on to uke, in koshi gurum tori's hips pass through a tad so uke is almost coming across part of the back of tori. One could write that one of toris buttocks (Right) passes through and not remains on front to form a block for the action of that wheel. This is where the kuruma action takes place. If the Right hand of tori is weak and does not have control over Uke the throw will fail. If the hara is not placed in the correct position, the throw will fail. It is not an easy waza to pull of if performed correctly, and that's generally a very big IF
One must examine the principle of kuruma waza. I like to teach O guruma as the first kuruma waza to introduce tori to the idea of a whirling throw
It is impossible to make a slow kuruma, it is the speed of entry and the body action that produces that wheeling action and this cannot be performed slowly.
If we take a piece of paper and draw a large circle and a smaller circle inside that large circle this is a kuruma waza. The hands make the outer circle while the hips or hara make the inner circle, the axis for the throw. This is the same even for Yoko guruma! Though yoko guruma is a yoko sutemi waza that wheeling action is still to be achieved by the action of the hands and the hips, the added advantage in the yoko guruma is the power in the throw comes from the whole of the body.
So, examine first the o guruma, ensure tori does not push ukes hips back with his leg BUT wheels uke around that outstretched leg, the leg is the fulcrum or pivot-axis for the hands to wheel uke over, velocity is needed to ensure the kuruma is a kuruma and not a pull over the leg.
Once the o guruma is studied it is much easier to begin with the koshi guruma, kata guruma etc.
The Right arm of tori cannot grip past the spine of uke as this then becomes holding the same side of the gi and one cannot do that.
This is a very misused waza by children who in actual fact are not performing a real koshi guruma but more of an illegal kubi nage. Kids naturally hold uke completely
around the neck, its what they do in the play ground before they ever hear of judo! In judo this is a major cause for broken clavicles. Tori dives the poor Right shoulder of uke into the mat and snap. Its a vital waza in self defence though.
If you where confused before I guess you are now snookered!