When the three principles are put into practical use, there are six concepts that grow out of their interchange. Tomiki Sensei drew these concepts from the much broader framework of martial arts, both modern and Old School (koryu). None are original with him.
They are different from the principles because they can be measured and gauged as well as experienced. They are presented here in related pairs, but all six concepts are dynamically related to each other.
Simply put, this is the minimum distance at which your opponent cannot attack you without movement. Ma’ai has three aspects: your position relative to your opponent, the speed required to cover the relative distance and the rhythm of movement with your opponent. Because movement is a dynamic process, ma’ai changes constantly.
A related term is issoku itto no ma’ai, the distance you can cover in one step to reach your opponent.
Literally, metsuke means eye contact. By looking at your opponent’s eyes (which are the window to his soul), your peripheral vision is much better able to detect even his slightest movement. A combination of concentration and awareness is required in interactions with your opponent. Visual and mental perception must be broad even while focused.
This is very much like perception while driving a car. The focus is on the road, but the peripheral vision is constantly engaged as well.
Center line of body where you are mechanically strongest when keeping your elbows close to the body. Stability is reduced when the center is moved away from this line.
We use tegatana to defend this center line and apply techniques.
Tegatana means hand sword. To implement: fingers together (not splayed apart), thumb extended, and energy flowing from your center and focused on the blade of the hand. Aikido applies sword and weapon principles to empty hand fighting. We use the sword hand as a shield, just as a fencer uses the blade of the sword. Tegatana is used most effectively when it is in your center with your power concentrating through it while using quick footwork and maintaining a strong and mobile posture.
The concentration of power through one point; in most cases through the use of tegatana. Tegatana can be applied to multiple spots on the body but still utilizing toitsu ryoku.
The coordinated, controlled and effective movement of the body. It is connecting whatever is being moved to the source of power in the most direct way possible.