"Sparring which begins with both the offensive and defensive opponents seated and facing each other is called iai."

Funakoshi G. - Karate-do Kyohan - The Master Text

"There is a type of practice done from a sitting position (suwari geiko), which existed not only in karate but in judo, aikido and other martial arts.

Although beginners were made to practice it at one time, it disappeared rather suddenly. Whether this was because it was considered useless or because it was too severe (that is, too much for the youth of today) is unclear. Perhaps practice from a standing position was thought to be more convenient as a starting point. But the contrary is true.

The first point with regard to this type of practice is that the hips and legs are greatly strengthened. Every movement must be based on the hips. In practice from a standing position, the hips may not be strengthened much. Thus, regardless of its severity, practice from a sitting position is necessary if the hips are to become strong and supple.

Moreover, even those who have practiced from a standing position for years should, I believe, practice from a sitting position in order to confirm whether they are actually using their hips in executing movements. The outcome may be that they are not even able to move when they try to practice this way. Such people should start all over again.

The second point is the development of a body that is soft and flexible, without which one's movements cannot flow smoothly, and one cannot execute a technique fully."

Egami S. - Karate-do: Beyond Technique