Literally meaning “Fourth Principle”. The technique is part of the base immobilizations (Osae Waza).
Yonkyo, base immobilization (Osae Waza) of the technical repertoire of Aikido with Ikkyo, Nikyo, Sankyo and Gokyo.
In general, we can define Yonkyo as a technique that consists of controlling the axis of the attacker’s body by controlling their wrist and forearm.
Performed habitually from Ikkyo in its Omote and Ura forms, Tori blocks Uke’s wrist by grabbing the inside of the wrist, forming a single segment on their forearm. Tori’s second hand is placed over the first one in such a way that he will remember the grip of the bokken. Keeping Uke’s elbow up or forward, the fundamental part of this manoeuvre involves Tori simultaneously shifting his body weight along with the rotation of his hips, thus removing Uke’s balance and causing them to fall face down.
For the final control in the Omote and Ura forms performed in Tachi Waza, Tori will remain standing, keeping the grip on the wrist and forearm pressing forward in the direction of Uke’s shoulder.
However, for the forms performed in Suwari Waza, Tori will use their knee to add pressure from inside Uke’s elbow.