KINETIC ANALYSIS OF THE UPPER LIMBS IN BASEBALL TEE-BATTING UNDER LOW HITTING POINT HEIGHT CONDITION

Hitting low height balls is more difficult for baseball batters in comparison to hitting high and middle height balls. The purpose of this study was to investigate the kinetic features of the individual upper limb joints among different skill level players in baseball tee-batting under the low hitting point height condition. Twenty-three collegiate baseball players were instructed to hit three kinds of hitting point height balls. Kinematic and kinetic analyses were implemented together with a motion capture system and an instrumented bat. The findings indicate that highly skilled batters exert great extension torque of the barrel-side (top hand) shoulder joint in the first half of the forward swing period in order to hit low point height balls. It is speculated that the large initial flexion angle of the barrel-side shoulder joint can help to increase the torque and angular velocity of the shoulder joint

KINETIC ANALYSIS OF EACH HAND IN BASEBALL BATTING MOTION AT DIFFERENT HITTING POINT HEIGHTS

The purpose of this study was to clarify the kinetic features of each hand under conditions of different hitting-point heights in the baseball tee-batting by using a bat with instrumented grip-handle. Twenty-three collegiate male baseball players’ motion were captured with a VICON MX system (12-cameras, 250Hz), and kinetic data at each hand were measured by using the instrumented bat equipped with 28 strain gauges (1000Hz). The vertical displacement of the hitting-point on the bat was mostly dominated by translational movement of the bat. The work of the force of vertical component showed that the positive work of knob-side hand was significantly larger at down swing and level swing phases. These results indicate that the knob-side hand is a great contributor to adjust the bat into the different hitting-point height in each phase

A SIMULATION ANALYSIS ON EFFECTS OF THE UPPER BODY MOTION ON BAT-HEAD SPEED IN BASEBALL BATTING

The purpose of this study was to explore for optimum motions of the upper body in order to generate a high bat-head speed through computer simulation of baseball tee batting. A bat and upper body nine-segment computer simulation model was developed. The model has totally 17 degrees of freedom at individual shoulder, elbow, wrist and torso joints. The optimisation procedure for the performance improvement was carried out by varying values and timings of joint angle in order to increase the bat-head speed to 40 m/s at the ball impact. The changes in the joint angular velocities about the shoulder internal/external rotation and elbow flexion/extension axes of the knob-side contributed to increasing large bat-head speed. These joint angular velocities of the shoulder and elbow affect to the horizontal movement of the in the forward direction before ball impact

LOWER BODY SIMULATION ANALYSIS ON INCREASING ROTATIONAL VELOCITY OF LOWER TRUNK IN BASEBALL TEE BATTING

The aim of this study was to investigate optimum timings of joint toques of the lower extremities in order to generate larger angular velocity of the lower trunk through baseball tee bating. A lower body seven-segment computer simulation model was developed. The model has totally 17 active torque generators at individual hip, knee and ankle joints, and torso joint. The optimisation procedure for the performance improvement was carried out by varying timings of exerting joint torques to maximise the peak forward angular velocity of the lower trunk about the vertical axis. The difference in exerting timing of the hip and knee joint torques of the stride leg contributed to increasing the peak angular velocity of the lower trunk, and that of the pivot hip flexion/extension joint toque prior to the impact contributed to the inhibition of the excessive rotational movement of the lower trunk

A CASE STUDY OF THE GENERATION OF ANGULAR MOMENTUM AND ANGULAR VELOCITY IN SOMERSAULT BACKWARD STRETCHED WITH 2/1 AND 3/1 TWISTS PERFORMED BY A SINGLE VARSITY MALE GYMNAST

The purpose of this study was to compare the angular momentum and angular velocity in somersault backward stretched with different number of twists performed by a single varsity male gymnast. The 3D motion captured system (Qualisys, 250Hz) was used to collect kinematic data of a single varsity male gymnast A who performed the somersault backward stretched with a double (2/1) and a triple (3/1) twist. The angular momenta and angular velocities of the body segments and whole body were calculated by the Tang’s method. More than a half of the twist angular momentum of the whole body in both 2/1 and 3/1 twists was generated during the take-off phase, which indicated that the gymnast A was classified as a contact twist type. In case of the gymnast A there seemed no difference in angular momenta of 2/1 and 3/1 twists, although he generated the angular momentum of the twist earlier in 3/1 than 2/1. He controlled the number of twists by his body maneuver before landing. Since these findings were obtained from a single gymnast, we need to investigate twist techniques and angular momentum date of various gymnasts

野球の打撃における上肢のエネルギーフロー : バット・ヘッドスピードの上位群と下位群のスイング局面の比較

This study examined the flow of energy in the right and left upper limbs of skilled baseball batters during the forward swing motion at different bat head speeds to obtain basic insights that would be useful for batting coaching. The subjects were 23 college baseball outfielders in university teams. The subjects were instructed to hit a ball toward the pitcher from a tee set at a mid-height position. Measurements were taken using 47 points on each subject’s body and 6 points on the bat for a total of 53 points, onto which reflective markers were attached. The 3D coordinates of each marker were measured using a 3D optical motion capture device (Vicon Motion Systems’ VICONMX, 12 cameras, 250 Hz). The variables in the kinetics of each hand were measured using a force detection sensor bat (1000 Hz). The subjects were separated into a faster group of 36.8±0.8 m/s and a slower group of 34.7±1.1 m/s for analysis. In terms of energy transmission, the data revealed that the faster group, in addition to showing additional torque on the knob side shoulder joints, were able to transmit more mechanical energy from the knob side shoulder joints to the end of the upper limbs than the slower group, and that this might be related to an efficient bat head speed. In addition, the faster group showed an increased positive torque power, and transmitted greater mechanical energy to the bat from the hand region. In other words, to prevent mechanical energy from being absorbed while adjusting the bat trajectory near the time of impact, skilled bat control involving movement of the hand joints appeared to determine the bat head speed

野球打撃における身体の回転運動に対する下肢のキネマティクスについて : 地面反力によるモーメントの上位群と下位群の比較

The purpose of this study was to investigate the kinematic characteristics of the lower limbs in relation to the rotation movement of the body based on the moment of the ground reaction force. Twenty-two male collegiate baseball players (age: 19.8 ± 1.3 yr, height 1.75 ± 0.04 m, body mass 73.9 ± 6.2 kg, athletic career:12.1 ± 2.1 yr) participated. They performed baseball tee-batting, set at middle ball height for the strike zone. Threedimensional coordinate data were acquired with a motion capture system (Vicon-MX), and ground reaction force data for both legs were acquired with 3 force platforms. High and low groups (HG and LG) were categorized by the mean peak moment around the vertical axis of the body’s center of gravity caused by the ground reaction force. The period analyzed was that from stride-side foot contact with ground until ball impact, and 2 phases were defined as follows: backward phase, stride-side foot contact with ground until the peak moment of the ground reaction force; forward phase, the end of the backward phase until ball impact. Statistical analysis was conducted using an independent t-test between HG and LG (p <0.05), and the effect size was calculated (small: d = 0.2; middle: d = 0.5; high: d = 0.8). In the backward phase, the flexion angle of both hips was greater in the HG than in the LG at event1 (pivot-side: d = 0.74; stride-side: d =0.97). The abduction angle of the pivot-side hip was significantly greater in the HG than in the LG (stride-side foot contact with ground: d = 0.94; peak moment of the ground reaction force: d = 1.44). In the forward phase, the external rotation angle of the pivot-side hip was significantly greater in the HG than in the LG (d = 1.02), which contributed to the inter-group difference in the internal rotation angle at the instant of stride-side foot contact. These results indicate that the motions of both hip joints acted to rotate the whole body around the vertical axis effectively. The knowledge obtained from this study should provide useful suggestions and insights into coaching for movements of the lower limbs in order to improve batting performance in relation to the rotational movement of the body

Optimisation of the upper body motion for production of the bat-head speed in baseball batting

The purposes of this study were to 1) develop a simulation model of baseball batting utilising the standard motion, and 2) explore optimal motions of the upper body to increase the bat-head speed. Twenty-three male collegiate baseball players performed tee batting set at waist height. A ten-segment angle-driven simulation model consisting of a bat and upper body was driven using with the coordinate data of the standard motion. Performance optimisation was conducted to find joint angle time histories of the upper body that increase the maximum bat-head speed. In the evaluation of the simulation model, the root mean square error between the measured and simulation model was 0.19 m/s and 0.98° for the time histories of the bat-head speed and bat orientation angle. Performance optimisation was able to achieve a targeted increase in bat-head speed (35.6 m/s to 40.0 m/s) through greater barrel-side shoulder abduction, knob-side elbow flexion, and torso right lateral flexion around ball impact resulted in the bat accelerating in the hitting direction. It is concluded that the proposed simulation approach can be applied as a tool for further simulation analysis in various complex sporting motions

Motor imagery ability in baseball players with throwing yips.

The motor imagery ability is closely related to an individual's motor performance in sports. However, whether motor imagery ability is diminished in athletes with yips, in whom motor performance is impaired, is unclear. Therefore, this cross-sectional study aimed to determine whether general motor imagery ability or vividness of motor imagery specific to throwing motion is impaired in baseball players with throwing yips. The study enrolled 114 college baseball players. They were classified into three groups: 33 players in the yips group, 26 in the recovered group (previously had yips symptoms but had resolved them), and 55 in the control group. They answered the revised version of the vividness of movement imagery questionnaire (VMIQ-2), which assesses general motor imagery ability. Furthermore, they completed a questionnaire that assesses both positive and negative motor imagery vividness specific to baseball throwing. In the former, they responded to their ability to vividly imagine accurately throwing a controlled ball, whereas in the latter, they responded to the vividness of their experience of negative motor imagery associated with baseball throwing, specifically the image of a wild throw. No significant difference in the VMIQ-2 was found among the three groups. While no significant difference in the vividness of positive motor imagery for ball throwing was found in either first-person visual or kinesthetic perspectives among the three groups, the yips group exhibited significantly higher vividness of negative motor imagery than the control group in both perspectives. These results indicate that negative motor imagery specific to baseball throwing may be associated with symptoms of yips. Therefore, interventions addressing psychological aspects, such as anxiety, which are potential causes of the generation of negative motor imagery, may be necessary to alleviate the symptoms of yips