Principle of double spiral
Ofen in a desire not to teach information that is to advanced for the aikidoka advanced principles get over looked. In the sequencing of teaching the principle of circularity first we teach circle, then spiral, and the double spiral which has the most to teach about, often gets lost. The techniques that teach this principle can be dangerous and result in injury so it becomes difficult to demonstrate safely.
With the use of the jo however, it can be taught for students to play with in their own way.
First, we need to understand the importance of the open grip where the jo is held loosely.
Also we do practices with the bokken where we use the top hand for navigation and the left hand for power, uses this principle.
We teach secondly the ability to extend ki through the jo or shodo o seizu by touching first with the index finger. With this practice imagine extenting ki in a spiral up and out the jo. Feel the difference in the stability of the jo. Thirdly, do the same with your other hand but spin the spiral in the opposite direction as the the first hand. Notice the difference in ki exception, centering and power.