The popular Facebook group “Aikido” shares well-written content about the traditional martial art, and the technical notebook.
Aikido students usually have trouble finding the spot on which to apply the pressure, and also how to apply one’s grip on uke’s wrist. Some precision is needed.
The grip is actually quite the same as the sword grip. The hand positions are twisted inwards, the power of the grip is in the little finger. If you grab uke’s wrist in much the same way as you should grab a sword, you are on the right track.
It is the base knuckle of your front hand index finger that is doing the yonkyo pressure. Still, don’t let go of the little finger grip of uke’s wrist – that will just lessen the effect. Again, it’s how you would manoeuver a sword, for example when pressing the tip of the sword down.
The base knuckle of your index finger presses into the flesh of the inside of uke’s wrist, and then turns outward to the lower arm bone on the thumb side of uke’s arm. It is this turning that causes the pain, not the initial pressure.