Recently, the giant on the horizontal bar is placed as a fundamental and important exercise. In this paper, the analysis of the giant swing (forward) was made by the motion and the electromyographic studies. To analyze the loci of the shoulder joint, the center of the gravity, the hip joint and the ankle joint, and the angle changes of the shoulder and the hip joint, the pictures of the 16mm film were used. Detailed observation of the movement was carried out from the view point of the functional mechanisms of the muscles of the shoulder girdle, the upper and the lower extremities. The electromyographic recordings were made with a 13-channel electroencephalograph (Sanei Instrument Co., Ltd.) using surface electrodes, 10mm in diameter. A motion picture and an electromyogram were taken simultaneously. The subjects were six gymnasts who were active participants in apparatus gymnastic for 4-10 years, including third place winner (horizontal bar) in Mexico Olympics (E. Kenmotsu). To get the kinetic energy for performing one circle, it was needed to stretch the radius of rotation when rotating downward and to shorten when rotating upward. When the body was rotated downward, two subjects performed with shortened posture (namely, the trunk was pulled upward) at the shoulder joint, three subjects moved from stretched posture (the trunk was pulled downward) to shortened posture, only the Olympic gymnast maintained stretched posture at the shoulder joint. On the latter half of the downward rotation, four subjects performed with the extended hip posture. But two did not perform with such a posture. From the above, it might be considered that when the body was rotated downward the stretched posture at the shoulder joint and the straight posture at the hip joint were advantageous for stretching the radius of rotation. When the body was rotated upward, the radii of rotation of the five subjects were shortened by the shoulder extension and the hip flexion. But in the case of the Olympic gymnast flexion at the hip joint could hardly be seen. So the Olympic gymnast shortened the radius of rotation mainly by the shoulcler extension. From this, it might be considered that, even if the hip joint was not so much flexed, circling was made possible and the motive power of the giant swing (forward) was due to the shoulder extension.