Japanese Journal of Biomechanics in Sports and Exercise
Online ISSN : 2434-4621
Print ISSN : 1343-1706
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  • Ryuji Kawamoto, Toshiharu Kawachi, Osamu Miyagi, Hiroshi Tanaka, Sho T ...
    2020 Volume 24 Pages 1-7
    Published: 2020
    Released: July 03, 2020

    The purpose of the present case study was to clarify calligraphic skill of a Japanese calligrapher quantitatively. For this purpose, the brushwork of an expert calligrapher was kinematically compared with that of a novice as well as an intermediate. Three subjects (an expert calligrapher, an intermediate, and a novice) participated in the experiment. A motion capture system was used to capture the motion of a brush during writing a kanji on a Japanese writing paper. As results, absolute writing speed tended to fasten and the variability of the vertical displacement of a brush decreased along with the calligraphic skill. The frequency analysis of the horizontal velocity of a brush revealed that a dominant region shifted toward a low-frequency direction in the expert in comparison with the intermediate although their absolute writing speeds were not significantly different. These results suggest that the expert calligrapher could move the brush with rather slow than rapid change of velocity on the horizontal plane accompanying with lowering the vertical brush displacement.

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  • Hirotaka Nakashima, Yoshitaka Morishita, Kentaro Yagi, Shinji Sakurai
    2020 Volume 24 Pages 8-18
    Published: 2020
    Released: July 06, 2020

    In baseball, the flight distance of batted balls is influenced by not only the batted ball velocity but also the spin. Previous studies reported that balls batted toward the opposite field (right field for the right-handed batter) had greater side spin and curved horizontally. If batters could impart less side spin to the ball, flight distance would be expected to increase because the ball would travel more linearly. The purpose of this study was to investigate how the spin of a batted ball is affected by the vertical bat angle at impact. A pitching machine was used to launch balls toward a fixed bat. The bat was positioned at six different angles under two conditions; the bat's long axis was adjusted horizontally and the bat head was declined 40° lower than the bat grip. The batted ball spins resulting from the batted ball angles were compared between the conditions. There were significant correlations between the horizontal batted ball angle and the side spin of the batted balls in both conditions. There was no significant difference between the slopes of the regression lines for the conditions. In brief, balls batted toward the same direction had similar spin regardless of the conditions. Therefore, it is suggested that the batters should not attempt to control batted ball spin, and increasing their bat swing speed would be still the most important key factor to hit balls long distances toward the various directions.

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