The purpose of this study was to investigate the differences of the motions between the speed throw and the distance throw , using a three − dimensiona1( 3D )motion analysis . Twenty − four male university baseball players were the subjects of this study . They were asked to throw a ba11 ( mass O, 144 kg)horizontally as fast as possible ( speed throw:ST ) , and as far as possible ( distance throw : DT ). These motions were filmed by two high − speed video cameras . 3D 且 andmark coordinates of the subiects and the bah were calculated by the DLT method . The foUowing kinematic parameters were computed :angle of release , the component velocities of the baU, the 3D angles for the backward! forward iean, right ! left lean of the upPer torso, and the twist of the torso and those for the abduction ! adduction , horizonta1 且exion ! extension , intemal ! external rotation at the shoulder joint , and the 且exion / extension at the elbow joint of the throwing arm . The sequential data were nor ・ malized with the time from the stride foot contact to the ball release , and then averaged . Angle of release was signi 盒cantly larger in the DT than in the ST . Signi 且cant dif 驚 rence was not found betWeen the resUltant velocity of the ST and the DT . Vertical velocity of the ball was sigriificant − lyぬrger in the DT than in the ST during the latter half of the acceieration phase , On the other hand , horizontal velocity of the ball was significantly larger in the ST than in the DT . The backward lean and the left lean angles of the upper torso were also significantly larger in the DT than in the ST throughout the all sequences analyzed . Ranges of these angulardisplacements between the stride foot contact and the release , however, had no significant dlfference betWeen the ST and the DT . The shoul ・ der adduction angle was also significanUy ger in the DT than in the ST during the latter half of the acceleration phase . These results indicate that the differences in the release parameters between the ST and the DT were caused not only by the throwing arm motions but also by the motions of the upper torso. It has been suggested that the motions to upward and 皇 eft ward of the upper torso helps to achieve longer throwing distance in the DT , and that forward lean of the upper torso possibly contributes to achieve brger horizontal ball vel ity at the release in the ST .
Base stealing is an important tactic for increasing the chance of scoring in baseball. This study aimed to compare the crossover step (CS) and jab step (JS) starts for base stealing start performance and to clarify the differences between CS and JS starts in terms of three-dimensional lower extremity joint kinetics. Twelve male baseball players performed CS and JS starts, during which their motion and the force they applied to the ground were simultaneously recorded using a motion-capture system and two force platforms. The results showed that the normalised average forward external power, the average forward-backward force exerted by the left leg, and the forward velocities of the whole body centre of gravity generated by both legs and the left leg were significantly higher for the JS start than for the CS start. Moreover, the positive work done by hip extension during the left leg push-off was two-times greater for the JS start than the CS start. In conclusion, this study has demonstrated that the jab step start may be the better technique for a base stealing start and that greater positive work produced by left hip extension is probably responsible for producing its larger forward ground reaction force.
: A three-dimensional (-D) videography study was performed to clarify the mechanical e#ects of a change of pitching motion from an overhand throw (OH style) to a three-quarter throw (TQ style). Two collegiate pitchers (subjects A and B) who normally used the OH style participated. They were requested to change their original OH style into the TQ style. To do this, they were subjected to a one-year skill training program based on biomechanical principles and on knowledge such as the stretch-shortening cycle theory, muscle force-velocity relationship, and the motions of skilled pitchers (e.g., shoulder positioning at 3* degrees of abduction-adduction during the acceleration phase). Four pitches for subject A (two in pre-training, one during training and one in post-training), and three for subject B (one each in pre-training, training and post-training) were videotaped with the -D DLT procedure using two high-speed cameras, and then analyzed. We then examined the mechanical di#erences between pre-and post-training. The speed of the ball at release increased progressively with every successive pitch for both subjects (Subject A : +-/.* km/h ; -rd : +-3.-km/h). The pitching styles of both subjects changed from their original OH style to the TQ style, both qualitatively and quantitatively. The time-dependent patterns and peak values of the angular velocities of shoulder internal-external rotation and elbow flexionextension of the throwing arm did not change very much. However, the peak value of the angular velocity of shoulder internal rotation occurred immediately after ball release for the OH style, while for the TQ style it occurred at ball release. As a result, the angular velocity of elbow extension at ball release was larger in the OH style than in the TQ style. On the other hand, the angular velocity of shoulder internal rotation at ball release was larger in the TQ style than in the OH style. These findings suggest that the increase in the speed of the ball is dominated by elbow extension in the OH style, and by shoulder internal rotation in the TQ style.
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