Department of Sports Research, Japan Institute of Sport Sciences, Kita-ku, Tokyo, Japan.
PLoS One. 2021 Nov 30;16(11):e0260520. doi: 10.1371/journal.pone.0260520. eCollection 2021.
In the game of softball, the batter should possess the necessary skills to hit the ball toward various directions with high initial speed. However, because various factors influence each other, there are limitations to the range that can be controlled by the batter's skill. This study was aimed at extracting the impact characteristics associated with the launch speed/direction and batted ball spin and clarifying the important skills required to improve the batter's hitting performance. In our experiments, 20 female softball players, who are members of the Japan women's national softball team, hit balls launched from a pitching machine. The movements of the ball and bat before, during, or after the impact were recorded using a motion capture system. Stepwise multiple regression analysis was performed to extract factors relating the side spin rate. The undercut angle (elevation angle between the bat's trajectory and the common normal between the ball and bat: ΔR2 = 0.560) and the horizontal bat angle (azimuth of bat's long axis at ball impact: ΔR2 = 0.299) were strongly associated with the side spin rate (total R2 = 0.893, p < 0.001). The undercut angle in opposite-field hitting was significantly larger than that in pull-side hitting (p < 0.001). The side spin rate was associated with the undercut angle because the bat's distal (barrel) side inclined downward (-29.6 ± 8.7°) at impact. The ball exit velocity was higher when it was hit at a smaller undercut angle (R2 = 0.523, p < 0.001). Therefore, it is deemed desirable to focus on maximizing the ball exit velocity rather than ball spin because the ball-bat impact characteristics vary inevitably depending on the launch direction. Meanwhile, the use of the ball delivery machine and the slower pitched ball are the limiting factors in the generalization of the findings.
在垒球运动中，击球员应具备必要的技能，以高初始速度将球击向各个方向。然而，由于各种因素相互影响，击球员的技能所能控制的范围是有限的。本研究旨在提取与球的初速度/方向和击出球的旋转相关的影响特征，并阐明提高击球员击球表现所需的重要技能。在我们的实验中，20 名日本女子垒球队的女队员使用投球机击球。使用运动捕捉系统记录球和棒在撞击前后的运动。使用逐步多元回归分析提取与侧旋率相关的因素。下切角（球和棒的公共法线之间的棒轨迹的仰角：ΔR2 = 0.560）和水平棒角（棒在球撞击时的长轴方位角：ΔR2 = 0.299）与侧旋率强烈相关（总 R2 = 0.893，p < 0.001）。外场击球的下切角明显大于内场击球（p < 0.001）。侧旋率与下切角相关，因为棒的远端（桶部）在撞击时向下倾斜（-29.6 ± 8.7°）。当下切角较小时，球的出口速度更高（R2 = 0.523，p < 0.001）。因此，最好关注最大限度地提高球的出口速度，而不是球的旋转，因为球棒撞击的特征不可避免地取决于发射方向。同时，球的投送机和较慢的投球是结果推广的限制因素。
