Central body axis or seichusen
Aikido claims to be a circular method and even Kenji Tomiki made a point of it in his book “Goshin Jutsu”.
Circular movement such as twisting & untwisting is one of the motive forces for the whole body movement. To understand and feel correct circular movement you have to know and feel the central body axis or seichusen.
The advantages of circular movements
1.An easier transition from one technique to another as the completion of one technique would blend into the one that follows. In other words, a series of movements can be made without stopping between the movements.
2. A whip like motion like gyaku gamae ate could generate a lot of speed and a great impact as it hits a target.
Seichusen
A fundamental item in training martial arts is the control of seichusen, the axis of the body. As the definition of this term varies from school to school, let’s just consider here the vertical line from the top of the head which passes by the middle of your body, to the floor. (see pictures)
Seichusen is a virtual line and can only be understood by experience.
The classic interpretation would be that one considers that two standing people are equally centered. Yet even in neutral position, everyone has tensions that unbalance his body, even if it is stable and its column is vertical, the seichusen can be not correct. It is something that one learns to feel in oneself and to see in others.
When a person has a better seichusen than his opponent it becomes very easy for him to act. On the other hand, with a bad seichusen, even though the form will look the same to an untrained look, the technique will rely on muscular power, speed, etc …
Developing one’s seichusen is a fundamental practice.
Central body axis exercise
Keep the shoulder line, don’t use actively hip joints and don’t use the knees.
The turning of the central body (shoulder line and waist) creates tension in the abdomen. By releasing tension, the stored power can be used to generate spiral power. This will be discussed with “tenshikei”.
Keep your attention to the feeling of the central body axis, later you can use this feeling in other exercises and techniques.
Study Group Tomiki Aikido 