In baseball, an accurate impact of a ball with the “sweet spot” of the bat is absolutely imperative to slug the ball a great distance. Such a successful impact requires precise positioning of the bat in the right place at the right time. The purposes of this study were to determine the area on the bat in which the batted ball speeds were extremely high (the area defines sweet spot) and to describe the kinematic characteristics of the bat and the ball impact in the trials that the balls were hit outside the sweet spot (such a batting defines mishit). Twenty-six expert (collegiate or non-professional) baseball players were recruited and each player was asked to hit a baseball thrown by a pitching machine for 8–26 trials. Two high-speed cameras were used to record each hitting movement during the phase of ball impact at 1000 fps. Using the pool of data (the total of 1033 trials), the sweet spot was determined as the area in which the ratio of the batted ball to the bat head speed was higher than 1.13 (maximum value minus 0.05). The position of the ball at impact was represented as (a) the 3D position relative to the batsman’s body and (b) the 2D position relative to the bat-embedded reference frame. The results showed that the sweet spot was a 21×97 mm rectangle, having the center located at 145 mm from the bat head. The ball was hit successfully within the sweet spot in 341 trials and was mishit in 692 trials. In successful hitting, the ball thrown at the inside corner of the strike zone was impacted at a position closer to the pitcher than the balls thrown at the outside corner was impacted. In mishits in which the ball was hit more distal to the sweet spot, the 3D position of the ball at impact was located significantly closer to the pitcher’s side than in successful hitting. On the other hand, in mishits in which the ball was hit more proximal to the sweet spot, the 3D position of the ball was located significantly closer to the catcher’s side. Therefore, the accuracy of timing according to the pitching course is required for the successful hitting with the sweet spot of the bat.

The purpose of this study was to examine within-subject differences in bat-swing trajectory between intentional hitting towards the same field and towards the opposite field. 19 industrial league baseball batters and 16 collegiate baseball batters performed same-field hitting (SH) and opposite-field hitting (OH). The movement of the bat during the swing was recorded with two high-speed cameras (1000 fps) for 3D analysis. At the instant of ball impact, the striking surface of the bat faced towards the same field in SH and towards the opposite field in OH. The bat-head trajectory immediately before impact was directed obliquely upward in SH, whereas it was directed obliquely downward in OH. Throughout the swing, the projection angle of the bat on the vertical plane was greater in OH than in SH, and the ratio of the translational component of the bat-head speed to the resultant bat-head speed was significantly greater in OH than in SH. These results suggest that the characteristics of the bat swing in OH provide a suitable impact condition to drive the ball towards the opposite field, as evidence has demonstrated that (1) a batted ball is likely to travel towards the opposite field when the lower half of the ball is hit by a vertically inclined bat, and (2) the striking surface of the bat is unlikely to turn to face towards the same field when the contribution to the resultant bat-head speed is generated more by the translational component of the bathead speed than by the rotational component.

Introduction:Coaches are required to need to be able to evaluate players’ performance on the field. Therefore, in order to evaluate pitching motion regardless of the experience level of the coach, the a baseline of the criteria is needed. The purpose of this study was to create evaluation criteria for pitching motion that can be used in actual sports coaching.

Methods:In this study, we created evaluation criteria for pitching motion by extracting common elements from medical science papers, literature, and players’ subjective opinions. To examine the validity of the evaluation criteria, we scored the motion of Japanese Major League Baseball (MLB) and Nippon Professional Baseball (NPB) pitchers based on the evaluation criteria and conducted a correlation analysis of the evaluation scores and ball velocity. To analyze the objectivity and reliability of the evaluation criteria, we calculated the inter- and intra-subject agreement of the evaluation scores given by six former NPB pitchers, coaches, and medical staff who had experience working in the field of baseball.

Results:There was a significant positive relationship between the evaluation scores for the second half of the pitch and the maximum and average ball velocity. The intraclass correlation coefficient (ICC) for the evaluation scores within inter and intra subjects of the entire pitch phase were all above 0.7.

Discussion:The results of this study suggest that the evaluation criteria we have developed have a certain degree of validity, objectivity and reliability. This indicates that there is no significant difference between the observation skills of experienced baseball coaches and medical professionals and the evaluation criteria we have developed.

In recent years, as measurement devices have advanced due to sensor and information technology, we have been able to measure bat swing data just after baseball impact. Therefore, the purpose of this study was to examine the characteristics of a batter’s swing using batting skill assessments from baseball coaches with significant experience. Finally, the practicality and effectiveness of baseball coaching methods, particularly for batting, were verified through this study. The subjects were 25 male university baseball players (age: 19.8 ± 1.0 yrs, body height: 174.5 ± 5.4 cm; body weight: 72.8 ± 5.1 kg). The participants were instructed to hit the ball placed on a tee stand. Nine types of tee-batting positions (course / height) were set for each participant depending on the upper and lower limits of the strike zone according to the baseball rules. Our main findings were as follows: 1) The swing characteristics (Depth: swing time and vertical bat angle, Height: head speed, rolling angular velocity, bat radius of rotation, horizontal bat angle, and vertical bat angle, Course: rolling angular velocity) varied with respect to ball positions, 2) Through batting skill assessment by two baseball coaches with significant experience, a good batter’s swing can be characterized as high bat speed, short swing time, and high efficiency of rotational movement around the vertical axis. Additionally, the coaches suggested that for a good batter’s swing, the vertical bat angle should be stable and smaller than 9°. These results provide useful information on assessment of bat swing training methods and exercises to hit the ball to different positions. Furthermore, this study can aid baseball coaches and/or players to objectively analyze a bat swing of a player.