It seems fairly clear that Kenji Tomiki understood the educational value of simplifying complex systems. He took the myriad of complex movements of Daito Ryu and Ueshiba's early prewar aikibudo, and broke it down into a logical judo-like organizational system. It seems like he was searching for a way to practice and transmit the most basic parts of the aiki art in a periodic table of physical motion. The teaching forms he came up with are more or less the 10,000 techniques of Ueshiba's aikido condensed to a basic student curriculum. He made the exercises into three parts. Tandoku - solo practice. This kind of exercise is often called Aiki Taiso in other systems. Sotai is the paired work. Finally he had a kata of techniques, which would eventually become the 17. Here is a list from around 1960 (approximate guess)
For this article I wish to focus in on the Sotai Taiso 相対 体操 and how it has evolved. Essentially this exercise where the goal was not to throw, but to practice connection, timing and structure breaking. By the 1950s Kenji Tomiki 富木 謙治 was busy compiling a system of aikido based education he called the Judo Taiso 柔道 体操. During this time he formulated a blending and balance breaking exercise. Here we see Kenji Tomiki in that time period demonstrating it starting at 1:11. Clearly it was an important part of his work, as it appeared in both the film and his book Judo Taiso. Apparently it was standard practice as Yamada was demonstrating it in the film in the late 1950s or early 60s in this film @ the 4:00. In the more modern school run by Fujiwara in Japan they also practice it. In this film we can see them training using this exercise at the 7:46 mark. The film is interesting as it shows clearly that solo practice and Sotai Taiso 相対 体操 were an important part of the the practice.
1. One teacher attributed the diffusion of the release forms to Miyake Sensei. They said she taught it as a exercise at a seminar, and many of the American students codified and kata-fied it.
2. Another speculated that it might have come from Riki Kogure. Kogure is a prolific kata writer in his own right. Kogure was a major figure in the distribution of Tomiki lineage aikido in the United States and many students that learned under him have unique katas, such as the O waza Ju Pon or Big 10.
3. I think it is clear the releases come directly from Tomiki's work. We see the exercises already being formulated in the 1950s films and books. Attributing the work to Miyake or Kogure seems unlikely.