We move our body under various dynamic conditions when we play a sport oroperate a machine. In playing a sport often we have to make judgments in an instant, and so we sometimes perform in a different way from our image. It is said that we can get 70% of the information of our five senses from visual information. If illusions occur easily in our environment, we may lose our balance . For example, when we are in a train and gazing at another starting train, some people think our train is starting, whereas others think the other train is going . It is very important which imagination we have. If we think another train is beginning to start when our train is starting, we lose our balance. Even in the opposite case ; if we think our train is beginning to start when another train is going, we may lose our balance. In this paper we measured the movements of a human's center of gravity when he was gazing at a moving picture made by a personal computer in a darkroom . The resonance frequencies were measured in the case where subjects swayed from side to side, and the phase differences between picture vibration and human vibration were also measured. As a result, it was found that we tune in to the sway of picture, but don't continue to tune to it. In the first period we tune in to the picture, and then our movements are delayed step by step. Resonance frequencies exist between 0.1-0.3Hz, although they are different among individuals . The phase difference has the smallest value when we sway at a resonance frequency, and then the variance has also the smallest value.

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Reduction of tremendous medical expenses is a social task in Japan. As a discriminative strategy in swimming-pool management, a unique health improvement program has appeared which has effectiveness for "chronic atopic dermatitis". This would have a possibility for curing the disease and for reducing medical expenses. In this case study, the authors discuss the program, and the structure of the medical expenses in the economic society by using an "Input/Output analysis". This analysis shows the demand structures in industrial society according to economic activity. The sports industry should be expected to supply unique services such as the discriminative health improvement program in alliance with medical area, and to accumulate evidence of its effectiveness for reduction of medical expenses and health promotion.

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This paper describes the dynamics of Japanese bows and arrows. In "kyudo" (Japanese archery), archers twist the grip at the moment of shooting, to avoid the "archers' paradox" which is a change of trajectory of the arrow caused by the structure of the bow and the arrow. To investigate the relation between the trajectory of an arrow and the twisting force on the grip, we proposed a dynamic model simplifying three rigid limbs and two elastic hinge. And we made an experimental apparatus that can give a force to twist the grip, and performed a shooting experiment. We measured with a strain gauge the twisting force on the grip, the tension of the string, bending moment at the center of arrow, and the compressive force of the neck. After that, we performed a computer simulation with the model we suggested and compared its result with the result of the experiment. As a result of comparison we proved that the tendency of computer simulation is consistent with the experiment. Then using this model, we investigated the relation between the twisting force and the trajectory of an arrow. As a result of simulation, twisting force is shown to be specially important during the term from taking a stance to the beginning of the shooting.

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We have developed an apparatus whereby the repel force produced by the exertion of force on the start-grips at the start time can be measured and displayed on a large LED matrix display. Using this apparatus, athletes can train themselves while confirming their exertion of grip force. This apparatus also has the function of measuring the time between 2 points on the course and displaying the interval time. Since wave patterns are saved in a computer, useful information can be obtained by data processing. Using those data, we examined and compared the athletes' patterns of force exertion. As a result, maximum force and the degree of impulse were observed to be correlated with interval time. Therefore, in general, athletes with good interval time had rather stable wave patterns.

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The purpose of this study is to explain the manufacturing and marketing activities of the Kaneda Ski Manufacturing Factory in Toyama Prefecture from the end of the Taisho Era to the early years of the Showa Era. This study uses historical data from Toyama Prefecture during the Taisho and Showa Eras.The following conclusions are deduced ; 1) Johana Town had Tatenogahara ski ground and was a good environment forskiing. The "Take" ski was popular in Johana Town from the middle of the Taisho Era. Kaneda took interest in skis from that time, as he enjoyed skiing and was a carpenter. He started to manufacture skis from the latter half of the Taisho Era and to sell skis from the fifteenth year of that era. 2) The trend in ski goods in this period was from Austrian to Norwegian type, but as Kaneda did not manufacture bindings, the biggest obstacle for him in manufacturing was to achieve the proper curvature of the ski. 3) Kaneda was willingly coached about manufacturing by Tomesaburo Sakur aba. Kaneda was coached from the fourth year of the Showa Era for ten years. Because of the superior help he received, Kaneda was able to succeed in both the manufacturing and marketing of the product.

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The Internet, which was developed originally in the academic field among universities in US., is rapidly spreading to business and commercial fields . Application of Internet technology to the sports industry in Japan was investigated through establishing "Internet Tennis Japan" (http://www.tennis-japan.com), which is the first tennis site in Japan. It was found that the originality of the domain name, video clinic, mail exchange program, and displaying excellent foreign sites in Japanese was effective to attract visitors.

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