其他摘要：The functional mechanisms of the shoulder and shoulder girdle were studied anatomically and electromyographically while the body length was shortened or lengthened at the shoulder without any angle change in the sagittal plane. Electromyograms were recorded with a 13 channels electroencephalograph using surface electrodes, 10mm in diameter. Recording sensitivity: 6mm/0.5mV. The recordings obtained were examined from the anatomical view of the X-ray pictures of the various chinning postures. The results obtained can be summarized as follows. 1) The postural change from the lengthened chinning to the shortened one, that is, the elevation of the sternoclavicular joint was resulted from that the clavicle was lifted up with the fulcrum of the acromioclavicular joint. This resulted in that the scapula was slightly rotated downward, and the shoulder joint was slightly pushed out. 2) Lifting up of the sternoclavicular joint resulted in 8cm shortening of the full length of the chinning posture, about 4.9% of the body length. The postural change from the most lengthened chinning to the most shortened one increased about 40.9 degrees of the angle between the longitudinal axis of the clavicle and the spinal column, about 8.0 degrees of the angle between the spine of the scapula and the spinal column, and about 4.3 degrees of the angle between the spine of scapula and the longitudinal axis of the humerus. 3) The postural change from the lengthened chinning to the shortened one resulted in gradual increase of the discharge of the abdominal pectoralis major, the latissimus dorsi and the lower trapezius, in which the lines of muscle pull run effectively to support the body weight from the anatomical view point. The increase of the discharge of the lower trapezius was most remarkable. 4) The most lengthened posture was kept with only the discharge of the middle deltoid, and without the discharge of the abdominal pectoralis major, the anterior and the posterior deltoid, the infraspinatus, the teres major, and the upper trapezius, even when the body weight was added by 30Kg of weight and the recording sensitivity was increased two folds.
