本研究では、加速度とリズム、タイミングを総合的に表現し、伝達するツールを提案した。一般的に、身体性の経験技術は、言葉やジェスチャーで伝達される。それによって大まかなフォームは簡単に理解することができるが、力の変化を理解する事は困難である。なぜなら、(ある種の)言葉やジェスチャーは動きの流れしか伝えられないからである。そこで、力は加速度から求められる（F=ma）ことから、加速度に注目した。スポーツ熟練者から得られた加速度を可視化した表現に変えることにより、他者がその熟練者の経験技術を簡単コピーできるのではないかと考えた。そして、体につけた加速度センサの電圧変化をPCに取り込み、波形、音などにするシステムを考案した。このシステムを使用して、波形を見ることによる熟練者の自己修正と音による経験者間でのスイングの伝達などの検証実験を行った。その結果、熟練者の自己修正、経験者間の伝達の両方で上達が見られた。これにより、波形から力の変化を読み取ることができることが示された。以上の結果、ツールとしての有効性を実証することができた。

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The purpose of this study was to evaluate the activity of the shoulder muscles with various loads in the external rotational motion of the shoulder and to find the load in which only the inner muscles work mainly and the outer muscles don't work.

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The purpose of this paper is to clarify the historical developing process from the mid 1870s when baseball came in, to 2008, about the movement of the overhand pitch that is one of techniques of the pitcher in baseball. The result of this study can be outlined as follows. 　 When baseball came to Japan in the beginning of the 1870s, the pitcher must pitch the ball in an easy underhand motion. In 1895, American rules were translated into Japanese for the first time the history of overhand pitching started at this time. However, there was no pitcher's mound, therefore, the pitcher must generate the power of the ball by himself. As a result, torso movement that inclined toward second base, and, inclined toward home base developed. 　 In 1905, a new rule was introduced to Japan. This rule provided for the height of pitcher's mound to a maximum height of 15 inches. This change made the pitcher more able to throw down from a high position. As a result, the movement that inclined toward home base was emphasized. One more reason of this emphasis was the location of the strike zone. It was identified between a batter's knees and his shoulders on the basis of a vertical posture, therefore, a speedball up to the height of the shoulder was a good ball. To throw that kind of ball, movement like that was required. 　 At the end of the 1920s, the twisting of the waist during an arm swing was generalized. In addition, combination of the torso movement and limbs was utilized. There was gradually an increase of the attention to ball control behind this development. 　 From a rule of 1941, the pitcher was permitted to step back behind the pitcher's plate, before stepping to home base. As a result, the pitcher came to be able to make more of a driving force to the home base direction by rising up his leg up extremely high. In order to generate this power, a follow up movement developed; the twisting torso to the second base direction and s twist back to the home base direction. 　 In 1956, the strike zone was reduced to between the batter's knee and his "arm pits", on the basis of the "batting posture". As a result, the effect of the speedball in relation to the height of the shoulder came to be called "ball" which means not a strike. And throwing to the lowest height came to be the most important factor, therefore, the movement of the inclining torso which was seen since the beginning, came to be ineffective. And pitching in an inclined movement changed to a vertical movement of the torso. Because of this change, the subject of the pitcher changed from aiming to create big power pitches into stabilizing the control of the pitch. 　 In 1988, the height of the pitcher's mound was reduced from a height of 15 inches to 10 inches. Next year, the upper limit of the strike zone was dropped from "armpit" to "horizontal line at the midpoint between the top of the shoulder and the top of the uniform pants". In 1997, the lower limit of strike zone was dropped to beneath the kneecap. For those reasons, the pitcher began to put emphasis on control, especially, throwing the lowest ball became the most important subject, more so than before. To throw a lower ball, stability of movement was taken into consideration as well. This resulted in the twisting to the second base direction that had been seen since about the 1940s to become ineffective for the first time. And then, the movement of the arms and legs, such as a forward step with a twisting inward motion, a backswing whilst lifting an elbow, a forward swing with a torsion movement and the return of it, developed. As a summary, the vertical torso movement and the twisting direction to home base is the conventional movement technique of modern day overhand pitching of baseball.

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 The purpose of this paper is to categorize the overhand pitch which is one of the techniques of the pitcher in baseball from a movement structure aspect，and as a document in the historical development process from the mid 1870s when baseball came in, to 2008.

 Firstly, the overhand pitch can be roughly classified into two systems: “an inclined torso system overhand pitch” and “a horizontal torso system overhand pitch”. The former has common movement techniques of that of the inclined torso toward second base, and, the inclined toward home base. On the other hand, the common movement technique of the latter is a vertical movement of the torso. This system of overhand pitch is primarily emphasized on control, especially, throwing the low ball.

 Secondly, two systems were categorized in to five types as follow. On the one hand, “an inclined torso system overhand pitch” are classified into three types. Number 1, “a movement of only inclining the torso type” which depend on the power of the incline torso movement. Number 2, “an inclined movement of the torso and a twist of the waist type” by incorporating the twist of the waist during an arm swing. And number 3, “an inclined movement of the torso and torsion return of the waist type” by a follow up movement: the twisting torso to the second base direction and a twist back to the home base direction. On the other hand, “a horizontal torso system overhand pitch” can be divided into two types. The first is “a horizontal torso movement and torsion return of the waist type” that incorporates a vertical movement of the torso and the twisting movement of the torso to the second base direction and a twist back to the home base direction. Another type of this system is “a vertical movement of the torso and a twist of the waist during an arm swing type”. With regard to this, the following movements are omitted: a torso movement that inclines toward second base, the twisting torso to the second base direction and a twist back to the home base direction. Therefore, this type of overhand pitch emphasizes movement stability.

 Thirdly, these types of overhand pitch can be divided by adding an additional standard of “the movement of limbs”: The category of “an inclined movement of the torso and torsion return of the waist type” can be divided into two types by the movement technique to make a driving force: “made by an extreme rise of the leg type”, and “made by a driving of the pivoting foot type”. The former is to make a driving force by a reaction of rising up the leg extremely high. The latter is based on the movements that drive the pitcher’s plate by pivoting the foot. Moreover, the “a horizontal torso movement and torsion return of the waist type” can be classified into two types in regard to the backswing arm movement: “backswing by straight arm type”, and “backswing by a raised elbow type”.

 To summarize, with regards to the “movement of the torso and waist”, there are two systems of which can be classified into five types. By adding an additional standard of “the movement of limbs”, it is possible to classify them in to seven types.

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