著者

波戸 謙太 金堀 哲也 谷川 聡 梶田 和宏 奈良 隆章 川村 卓

出版者

日本コーチング学会

雑誌

コーチング学研究 (ISSN:21851646)

巻号頁・発行日

vol.35, no.1, pp.1-17, 2021-10-20 (Released:2021-12-28)

参考文献数

32

---

This study delineates the common characteristics of pitching motion in professional baseball pitchers by focusing on their lower limbs. Further, to gain an insight into the development of athletic capacity, the pitching motion of the Top group was compared with the Minor group, resulting in the clarification of lower limb issues in the Minor group. Data analysis was performed using a test with the highest score in a 5-point objective evaluation by the observer and the highest ball speed in the tracking data obtained from Trackman, with the following results: (1) The common characteristics in a professional baseball pitcher was that the hip joint was flexed while the stride leg knee joint angle was fixed to MBV (Minimum Ball Velocity), MER (Maximal Shoulder External Rotation), and the stride leg hip joint and knee joint were slightly extended to MER, REL (Ball Release). (2) Regarding the difference between the Top and Minor groups, it is suggested that the Top group accelerates the rotational speed of the lower torso to SFC (Stride Foot Contacts Ground), which increases the angular velocity of adduction of the hip joint of the stride leg, resulting in torsion of the trunk and stable force transmission after MBV. (3) In the Top group after SFC, the angular displacement and angular velocity was such that the hip joints of both legs were fixed. Additionally, the stride leg hip joint was in adduction, which caused the motion to increase the rotation of the lower and upper torsos. Authors suggest considering these key points while coaching baseball.

著者

梶田 和宏 川村 卓 島田 一志 金堀 哲也 八木 快

出版者

日本コーチング学会

雑誌

コーチング学研究 (ISSN:21851646)

巻号頁・発行日

vol.32, no.2, pp.171-187, 2019-03-20 (Released:2019-09-02)

参考文献数

55

---

This study clarifies the features of throwing motion to second base of professional baseball catchers.Eleven catchers of two Nippon Professional Baseball Organization teams were participants. Using the highest confidence data among analytical trials for throwing time, we defined it as ‘the time required from catching until ball arriving at second base with shortest time’. Following five characteristic features were revealed. 1) In time parameter, professional catchers have a difference in motion time (the time required from catching to release in amateur catchers), especially during the beginning phase having a relation with duration time (arrival time from the ball release to the second base), the throwing phase having a relation with the throwing time and release speed (speed average of ball speed of 3 frames after releasing the ball), and the grip changing phase having a relation with motion time. 2) Further, professional catchers have a tradeoff relationship between the motion time and the duration time as well as amateur catchers; and, particularly good professional catchers can shorten the duration time even while shortening motion time leading to shortening of the throwing time. 3) In stride parameter, professional catchers have a difference in the length of the pivot foot in amateur catchers, especially, the X component has a relation with the motion time while the Y component has a relation with the duration time, and the stride length is likewise; there was no relationship between all the items. 4) In release parameter, professional catchers maintain a higher projection height of the ball than amateur catchers and maintain the tendency of the projection angle to be lower, improving the throwing accuracy, especially the elevation angle is related to the duration time and the release speed, but the azimuth angle is likewise; there was no relationship between all the items. 5) In center of gravity of the body, professional catchers have a relation with the movement speed of the center of gravity of the body and the release speed as well as amateur catchers, but the moving distance of center of gravity of the body is likewise; there was no relationship between all the items.

著者

小倉 圭 川村 卓 金堀 哲也 野本 尭希 八木 快 小野寺 和也

出版者

一般社団法人 日本体育学会

雑誌

体育学研究 (ISSN:04846710)

巻号頁・発行日

vol.62, no.2, pp.511-522, 2017 (Released:2017-12-19)

参考文献数

25

---

The purpose of this study was to clarify the types of step adjustment performed by baseball infielders for catching a grounder in relation to skill level. The subjects were 18 amateur baseball infielders, whose fielding motions were videotaped using 2 high-speed video cameras (300 Hz). The 3-dimensional coordinates of both the toes and the ball were obtained using the DLT method. The top 9 subjects who showed small variations in the grounding point of both feet when adopting the catching posture were defined as a high-performance group, and the bottom 9 subjects were defined as an intermediate-performance group. The results obtained were as follows:  1) Baseball infielders modified each grounding point from 4 steps to 1 step before catching in order to acquire the most appropriate catching point, and the final step was highly reproducible.  2) The high-performance group showed a significantly smaller standard deviation in the 1 step before the grounding point than the intermediate-performance group.  3) In the high-performance group, there was a positive correlation between the standard deviation of step length 1 step before and the standard deviation of the grounding point from 5 steps to 2 steps before.  These results suggest it is important to reduce variations in the grounding point 1 step before by earlier perception of the error in the front-to-rear direction of the grounding point. These results could provide important insight for coaches or trainers attempting to improve the performance of infielders when catching a grounder.

著者

阿江 数通 小池 関也 藤井 範久 阿江 通良 川村 卓 金堀 哲也

出版者

一般社団法人 日本体育学会

雑誌

体育学研究 (ISSN:04846710)

巻号頁・発行日

vol.62, no.2, pp.559-574, 2017 (Released:2017-12-19)

参考文献数

46

被引用文献数

1

---

The purpose of this study was to compare the kinematic characteristics of the upper body between baseball tee batting and pitched ball batting in order to gain basic knowledge for improvement of batting skill. Ten male collegiate baseball players (age: 20.7±1.1 yr; height: 1.75±0.05 m; body mass: 76.3±7.1 kg; athletic career: 12.7±2.7 yr) participated. They performed 2 kinds of batting: tee batting (TB) and machine-pitch batting (MB) using a pitching machine (approximate ball speed 33.3 m/s), which were set at middle ball height for the strike zone. Three-dimensional coordinate data were acquired with a motion capture system. Kinematic variables such as maximum bat-head speed, swing time, bat angle, joint angles of the upper limbs, and segment angle of the upper trunk were calculated. Differences between TB and MB were analyzed statistically using paired t-test (p<0.05). The maximum bat-head speed was significantly greater in TB than in MB, but swing times divided into 2 phases showed no significant differences between MB and TB. In the first half of the swing, the bat inclination angle was significantly larger in MB than in TB. The joint angles of the barrel-side shoulder abduction, knob-side shoulder adduction and internal rotation were significantly larger in MB than in TB, and those of the barrel-side shoulder internal rotation and individual elbow pronations were significantly larger in TB than in MB. The clockwise rotational angle of the upper trunk was significantly larger in TB than in MB. In the last half of the swing, the joint angles of the barrel-side shoulder abduction, knob-side shoulder flexion and adduction were significantly larger in MB than in TB, and that of the knob-side elbow pronation was significantly larger in TB than in MB. The changes in upper body movement in MB affected the radius of rotation of the bat about the vertical axis to control the bat easily. The movements in the last half of the swing largely resulted from those in the first half of the swing, and did not contribute to timing adjustment. These results indicate that the initial configuration of the bat and upper limbs, and movements at the beginning of the bat swing contribute to the timing adjustment of the bat for a pitched ball. The results of the present study suggest that it could be useful to pay attention to the movement of the bat and upper body in the first half of the swing as TB practice in order to improve timing adjustment.

著者

金堀 哲也 山田 幸雄 會田 宏 島田 一志 川村 卓

出版者

一般社団法人 日本体育学会

雑誌

体育学研究 (ISSN:04846710)

巻号頁・発行日

vol.59, no.1, pp.133-147, 2014 (Released:2014-06-13)

参考文献数

28

被引用文献数

6 2

---

The purpose of this study was to clarify the viewpoint of a well-experienced baseball coach when evaluating batting skills using kinematics indices. Method: First, three baseball coaches evaluated sixteen baseball players in their own teams. The players were divided subjectively into a first superior (FG) group and a second superior (SG) group according to batting ability. Next, the hitting motion of all sixteen players was captured using a VICON system (9 cameras, 250 Hz). We measured the speed of the batted and pitched ball, or the timing of release by the pitcher, using three synchronized high-speed cameras (250 Hz). From these kinematics data, we calculated several kinematics indices for each batter, focusing especially on the indices for motion of the lower extremities and trunk. In contrast, a well-experienced expert coach who had never met these players evaluated the hitting motion of each player using only motion films without the above kinematics indices, and similarly divided them into FG and SG. The evaluation of fourteen players agreed between the team coaches and the expert coach. The FG and the SG each comprised seven players. We analyzed these fourteen players using the kinematics indices, and clarified objectively the differences in hitting motion between the two groups. Results & Conclusions: The speed of swing, batted ball speed and physical index were approximately the same in the two groups. However, players in the FG group showed a significantly longer distance of center of gravity migration in step than those in the SG group. This might have been attributable to the hip abduction movement on the pivot side on the basis of kinematics indices (p<0.05). Moreover, players in the FG group took more time in step, and swung in a shorter time after landing on the stepped foot, relative to the players in the SG group (p<0.05). These results suggest that the well-experienced expert coaches paid particular attention to the above hitting motion rather than the speed of swing, batted ball speed and physical index as coaching points.

著者

阿江 数通 小池 関也 藤井 範久 阿江 通良 川村 卓 金堀 哲也

出版者

一般社団法人 日本体育学会

雑誌

体育学研究 (ISSN:04846710)

巻号頁・発行日

pp.16080, (Released:2017-09-01)

参考文献数

48

被引用文献数

1

---

The purpose of this study was to compare the kinematic characteristics of the upper body between baseball tee batting and pitched ball batting in order to gain basic knowledge for improvement of batting skill. Ten male collegiate baseball players (age: 20.7±1.1 yr; height: 1.75±0.05 m; body mass: 76.3±7.1 kg; athletic career: 12.7±2.7 yr) participated. They performed two kinds of batting: tee batting (TB) and machine-pitch batting (MB) using a pitching machine (approximate ball speed 33.3 m/s), which were set at middle ball height for the strike zone. Three-dimensional coordinate data were acquired with a motion capture system. Kinematic variables such as maximum bat-head speed, swing time, bat angle, joint angles of the upper limbs, and segment angle of the upper trunk were calculated. Differences between TB and MB were analyzed statistically using paired t-test (p<0.05.) The maximum bat-head speed was significantly greater in TB than in MB, but swing times divided into two phases showed no significant differences between MB and TB. In the first half of the swing, the bat inclination angle was significantly larger in MB than in TB. The joint angles of the barrel-side shoulder abduction, knob-side shoulder adduction and internal rotation were significantly larger in MB than in TB, and those of the barrel-side shoulder internal rotation and individual elbow pronations were significantly larger in TB than in MB. The clockwise rotational angle of the upper trunk was significantly larger in TB than in MB. In the last half of the swing, the joint angles of the barrel-side shoulder abduction, knob-side shoulder flexion and adduction were significantly larger in MB than in TB, and that of the knob-side elbow pronation was significantly larger in TB than in MB. The changes in upper body movement in MB affected the radius of rotation of the bat about the vertical axis to control the bat easily. The movements in the last half of the swing largely resulted from those in the first half of the swing, and did not contribute to timing adjustment. These results indicate that the initial configuration of the bat and upper limbs, and movements at the beginning of the bat swing contribute to the timing adjustment of the bat for a pitched ball. The results of the present study suggest that it could be useful to pay attention to the movement of the bat and upper body in the first half of the swing as TB practice in order to improve timing adjustment.

著者

金堀 哲也 岡本 嘉一 小倉 圭 前原 淳 島田 一志

出版者

一般社団法人 日本体育学会

雑誌

日本体育学会大会予稿集

巻号頁・発行日

vol.68, pp.217_2, 2017

---

<p> 成長期の野球選手における野球肘の有病率は非常に高く、野球肘の早期発見および予防の重要性が提言されている。野球肘の発症要因には酷使をはじめとして、ポジションや投球動作など、様々な要因が複雑に絡み合っている。Okamoto et al.(2016)は、学童期野球選手を対象にMRI診断を行った結果、41.9%に異常所見がみられたものの、投球数、投球頻度、ポジションとの関係性はなかったと報告している。すなわち、野球肘の発症要因において、投球動作との関連性は少なくないと考えられる。そこで本研究は、肩・肘に痛みのない学童期野球選手60名を対象に、肘関節MRI診断および投球動作の3次元動作解析を併用することで、MRI診断結果と投球動作の関係性について検討し、野球肘の発症要因となる投球動作を明らかにすることを目的とした。その結果、踏出足着地時の投球腕肩関節の外転角度においてMRI陰性群のほうが有意に小さかった。また、踏出足着地時の肩と腰の回転角度の差においてMRI陰性群のほうが有意に大きかった。以上のことから、踏出足着地時の姿勢がその後の投球腕の動作に影響を及ぼし、肘関節への過度な負荷を加えている可能性が示唆された。</p>

著者

波戸 謙太 金堀 哲也 蔭山 雅洋 八木 快 谷川 聡 川村 卓

出版者

日本コーチング学会

雑誌

コーチング学研究 (ISSN:21851646)

巻号頁・発行日

vol.36, no.2, pp.159-176, 2023-03-20 (Released:2023-03-31)

参考文献数

44

---

This study delineates the common characteristics of pitching motion in professional baseball players (Top and Minor groups) by focusing on their upper body. With an aim to gain insight into the development of athletic abilities, the pitching motion of the Top group was compared with the Minor group, resulting in the clarification of upper limb issues in the Minor group and amateur pitchers. The subjects were 47 pitchers belonging to the Nippon Professional Baseball (NPB). The experiment was a fastball pitch with maximum effort. The analyzed trial was the highest ball velocity (average ball velocity 38.9 ± 1.8 m/s). Post-analysis, the following commonalities and differences were identified. (1) There is a commonality in the sizeable external rotation of the shoulder joint during MER (Maximum External Rotation), which is considered a factor in pitching speed compared to amateur pitchers. However, after evaluating the professional baseball pitchers, it was suggested that this movement had a low influence on the ball velocity. (2) There was a commonality in the movements in which the maximum shoulder horizontal adduction angular velocity was more significant than the upper trunk angular velocity. (3) However, in terms of differences among professional baseball pitchers, the Top group pitchers had a greater horizontal adduction angular velocity of the shoulder joint during MER and a more significant extension angular velocity of the elbow joint during REL (Ball Release) by suppressing the forward tilt angular velocity of the trunk during MER.

著者

堀 哲也 兼子 一重 水谷 照吉 石岡 貢

出版者

一般社団法人 電気学会

雑誌

電気学会論文誌A(基礎・材料・共通部門誌) (ISSN:03854205)

巻号頁・発行日

vol.123, no.7, pp.663-668, 2003 (Released:2003-10-01)

参考文献数

14

被引用文献数

1 2

---

The effects of temperature and electrode materials on space charge distributions of Linear Low-Density Polyethylene (LLDPE) polymerized with Ziegler catalyst were measured with the pulsed electro-acoustic (PEA) method. The thickness of a sample was about 100 µm. Positive space charge was dominant and it changed from homo to hetero space charge with temperature. The mobility of positive charge was 8.1×10-15 m2V-1s-1 at 23°C and 1.0×10-14 m2V-1s-1 at 30°C. On the other hand, the mobility of negative charge was 3.7×10-15 m2V-1s-1 at 30°C. The positive space charge accumulating near the cathode enhanced the electron injection and, as a result, the charging current. The electrode materials used were aluminum and semi-conductive polymer. The space charge distribution and the charge injection depended on electrode conditions.