By Mitsunari Kanai, 8th Dan, Shihan
Chief Instructor of New England Aikikai (1966-2004)
Chapter 3 – Principle of Body Movement (UNTAI NO GENRI)
Much of the language typically used in descriptions of AIKIDO technique reflects an overemphasis on footwork. Some common expressions reflecting this overly restrictive viewpointinclude feet/leg movement (HAKOBIASHI), footwork (ASHISABAKI), and treading (ASHIBUMI).The critical aspect of a technique is not in the movement of the feet and legs. This is becausewhen a body movement exceeds a certain speed, it is impossible for the feet and legs to followand keep pace. (Movement in the darkness where it is necessary to feel ones way along is anexception to the rule.)
Body movements naturally originate in the KOSHI which is the largest mass in the body. (TheKOSHI should be understood to include the entire hip area of the body, including the buttocks.)The center of the KOSHI is the TANDEN, and TANDEN is also the center of the entire body.In order for the human body to constantly maintain good balance, the KOSHI and the head(which is the body’s second largest mass) must be correctly aligned. When the weights of thehead and KOSHI become misaligned, the posture can be re-balanced or corrected (very subtlyin many cases) by moving and realigning the KOSHI and legs in a new position.Executing complicated body movements is made possible by this cycle of moving the weight ofthe KOSHI and the head, destabilizing the posture, and realigning these weights by moving thelegs and hips to a new, stable posture.It is important to begin to understand the relationship of the head and KOSHI.
However,because their relationship can become very complicated, a detailed explanation will bepostponed until later. For the remainder of this discussion, we will define KOSHI as includingboth the head and the trunk, that is, as the whole weight of the upper body that rests on theKOSHI.The entire upper body weight rests first on the KOSHI but then splits into two halves thatextend through the legs and eventually rest on the two feet. Thus, when the KOSHI moves, thebody weight will automatically shift. This results first in movement of the legs and feet, and thenin movement of the whole body. If the weight shift is slow, the reaction of the two legs will beslow as well.
Conversely, if the weight shift is fast, then the response will also be fast.Whether one realizes it or not, the ability to move freely in any direction is made possible, andis triggered, by movement of the KOSHI which generates momentum and in turn is followed by movement of the legs. If one wishes to make refined movements, it is important to beconscious of the function of the KOSHI and fully utilize it.Basic forward and backward movements can provide some examples of this process.First, consider forward movement. Begin from CHOKURITSU SHIZENTAI, i.e. a standing naturalposture where the weight of the KOSHI is resting on the two legs in a balanced way. If onemoves the KOSHI forward, one’s body weight would crumble forward (unless the head is pulledbackward to balance it).
In order to control this destabilization of the body weight, one leg willtend to move forward. A smooth repetition of this sequence creates a smooth forwardmovement (ZENSHIN UNDO).Conversely, if from CHOKURITSU SHIZENTAI one were to pull the KOSHI backwards, the bodyweight would crumble backwards unless one leg moves backwards. The repetition of this isbackward movement (KOTAI).Similarly, if from CHOKURITSU SHIZENTAI one were to shift the KOSHI to the right side, thebody would crumble towards the direction of the KOSHI shift. In order to maintain one’sbalance, the right leg must move toward where the KOSHI has shifted. Furthermore, if the otherleg then follows, it would create a side shift movement.Let us consider a second example, starting again from CHOKURITSU SHIZENTAI. If one twiststhe KOSHI to the left, it becomes evident that the KOSHI can move only up to a certain pointwithout beginning to pivot the feet.
Continuing to twist the KOSHI further to the left, beyondthis point, causes the tip of the toe to begin to move in the same direction as the KOSHI’smovement.Eventually, once the KOSHI twists and the feet pivot as far as possible, the toes and the KOSHIwill wind up pointing in almost the same direction. (Note that the “direction” of the KOSHI isdefined as the direction the TANDEN is pointing) This is especially true for the back leg (in thisexample, the right leg). Consequently, the whole body turns to the left and automaticallycreates the left natural posture (HIDARI SHIZENTAI).Let us consider a third example beginning from a SEIZA (sitting straight) position. From SEIZA,one begins to rise by first sitting on one’s toes and then, keeping the knees on the floor,stretching the KOSHI.
From this position, move the KOSHI forward and step forward with theright leg so the knee assumes an upright position.One can easily stand up from this position by stretching the backbone and the back muscles,and creating a posture in which three parts of the body form 90 degree angles: the insideangle of the upright knee, the inside angle of the knee on the floor, and the outside angle ofthe sole of the foot (which is already aligned vertically on its toes) and the heel (including theAchilles tendon). If the tips of both toes are pointing in the same direction as the KOSHI, then by simply straightening the rear leg and thereby extending it, one can easily and quickly rise toa standing position.Once standing up, one’s basic posture should be as follows: the right knee should be slightlybent and the lower leg (below the knee) should be aligned vertically. The rear leg should bestretched so as to function as a support stick (SHINBARI BO).
Finally, the upper body (with astretched back) should be aligned properly on the KOSHI such that the two legs evenly supportits weight. This form is the strongest standing posture, and is especially critical at the finalmoment of a technique when one projects the maximum output of power into the opponent.Therefore, when one has just finished executing a technique, one should be in this posture.Another feature of this posture is that if the front leg takes a long stride (and therefore there issufficient distance between the front and back feet), it is easy to immediately lower one knee tothe floor into an equally formidable and strong posture. Thus, when one wants to use adynamic technique that employs a quick movement from a standing to a (one knee) kneelingposition, it is important that there be an adequate span between the feet. If this is done, onewill be able to correctly perform the movement required by this type of technique.In all these examples, we see that all body movements are triggered by a KOSHI movementwhich, in turn, causes a weight shifting, and then, if balance and stability are to be re-established, necessarily leads to a compensating movement by both legs and feet. This is theprinciple of body movement (UNTAI NO GENRI)