THE RELATIVE POSITION OF “SEIKA-TANDEN” AND THE CENTER OF GRAVITY IN CORRECT SITTING POSTURE AND “KEKKA-HUZA”

The purposes of this study were firstly to observe relationship between positions of lower abdominal region (called “Seika-Tanden” in Japanese) and whole-body centers of gravity (CGs) in four types of the correct sitting posture (called “Seiza” in Japanese) and the sitting postures crossing legs on four conditions (called “Kekkahuza” in Japanese), and secondly to compare these postures by degree of spinal curvature which had measured with a conformateur. Four types of “Seiza” was prescribed as follows: (1) Tanza: incorrected “Seiza” , (2) Sokushinza: “Seiza” corrected with piling a top side in one foot on an arch of another foot, (3) Koushiza: “Seiza” corrected with crossing hallux, (4) Heishiza: “Seiza” corrected with placing toes side by side. Four conditions on “Kekkahuza” were (1) non-cushion, (2) one cushion, (3)add one more cushion, (4) add two more cushions. Estimation of CGs was based on H. Matsui's body segment parameters by means of pictures in profile. Positions of “Tanden” were obtained by T. Sato's drawing figure method. The subjects were eleven Judoist (on “Tanza” , “Sokushinza”,“Koushiza” and “Heishiza”) and a practician of “Zazen” (on “Kekkahuza”). The results were as follows:<br>1) As to characteristics in each posture estimated by degree of spinal curvature,“Tanza” characterized by a shape of that like an alphabet C, and the lumbar curvature was not found. On the other hand, the corrected “Seiza” (“Sokushinza”,“Koushiza” and “Heishiza”) and “Kekkahuza” expressed curvatures like an alphabet S that showed the same characeristics as a standing posture.<br>2) In both “Seiza” and “Kekkahuza”, the positions of CGs located above the navels, and the heights of CGs were higher than those of “Tanden”.<br>3) In“Seiza”, the antero-posterior positions of CGs were more behind than those of “Tanden”(50%).<br>4) About “Kekkahuza”, the antero-posterior positions of the CGs were in the rear of those of “Tanden” on all conditions (39.5-42.2%).