Multi-objective optimization of ski jumping flight was carried out, and then the trade-offs between the objective functions and the control variables could be visualized using Self-Organizing Maps. It was assumed that there are four objective functions and eighteen control variables in this case. Three of the four objective functions are concerned with the style point, and the other is the flight distance. It was found that that the longer the flight distance the smaller the style point. The forward leaning angle and the angular velocity in the nose-down direction should be almost 0 and 10 degrees at 0.3 seconds.

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Concerning most of track-and-field athletics such as the marathon, it is important to elucidate the flow around track runners, and to evaluate their air resistances. In wind-tunnel experiments which are the most effective approach to the study, the moving-belt device is indispensable for precise aerodynamic measurements considering the ground effect. In the present study, the authors develop the device, and show its basic performance such as the distributions of time-mean velocity and turbulent intensity above the moving-belt using a hot-wire anemometer.

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Balls used on rugby and American football are like prolate spheroids rather than spheres.Those balls sometimes autolotate, more specifically tumble, during their flights. The present study is a fundamental approach to reveal aerodynamic characteristics of such a prolate spheroid in tumbling motion. Specifically speaking, the authors conduct subsonic wind-tunnel experiments, in order to investigate the effect of the depth-to-width ratio λ upon the tumbling of a simple two-dimensional rectangular-cross-section prism. And the authors carry out the flow visualisation by a smoke-wire method and the velocity measurement by a hot-wire anemometer together with a synchronised prism-angle measurement. As a result, there exist two flow modes for λ < 0.6 and λ > 0.6. Especially at λ = 0.5, we can see transition-process features between the two flow modes.

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A shuttlecock, which used in the sport of badminton, has the smallest ballistic coefficient and exhibits the largest in-flight deceleration of any airborne sporting implement. The shape of the shuttlecock makes itself extremely aerodynamically stable. In the present study, in order to understand the aerodynamic characteristics of a shuttlecock, measurements of drag coefficient were carried out in a wind tunnel. Furthermore, flow visualization technique was also used to aid in understanding the relationship between fluid forces and the vortex behavior. The drag force of shuttlecocks is not significantly affected by the rotation (spin) rate and primarily related to the flow passing through the gap in the shuttlecock skirt in low Reynolds number. The drag coefficient for the shuttlecock with no gap becomes smaller in contrast to that for the ordinary shuttlecock, and therefore the drag is affected by the flow passing through the gap in the shuttle skirt.

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The turbo-jav is a flying object used in the javelic throw in the junior Olympic games. In order to investigate the aerodynamic characteristics of the turbo-jav, we measured the drag force, lift force and pitching moment which act on the turbo-jav in a low speed wind tunnel at the flow speed up to 25 m/s. Test results show that the obtained drag coefficient, lift coefficient and moment coefficient are almost constant irrespective of the Reynolds number when the flow speed is larger than about 12.5 m/s. The dependence of these coefficients on the angle of attack is examined closely. By the use of these obtained coefficients, we have made a numerical simulation of the flight of the turbo-jav at various initial conditions corresponding to throwing experiments. The trajectories of the turbo-jav predicted by the numerical simulation were found to be comparable to those of the throwing experiments.

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For the sake of an evaluation of ball velocity, flight angle, spin rate and spin axis of a spinning sports ball, an automated image processing system for an analysis of images during flight of the ball captured using a high speed video camera has been developed. The tested ball is marked with mutually perpendicular three great circles for the detection of its attitude. An ellipse which is the projection of the great circle on the image is detected by the generalized Hough transform. The ball attitude is decided by directions of three great circles. The spin axis and spin rate are calculated from variations of the ball attitude. From the analysis of experimental flight images of a table tennis ball using the developed system, it is found that the obtained results are accurate and reliable through the comparison with manually analyzed results and three-dimensional spin measurement is possible using only one camera.

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Japanese and U.S. baseball ball shape and seam height are measured by circularity measurement equipment. It was measured on the circumference side of the ball. Geometrical tolerance of the ball was measured with 4 seam and 2 seam side. U.S. seam height average lower than the Japanese ball about 0.23mm around 2-seam circumference. The distortion of the surface of the ball was calculated as standard deviation. Japanese ball are five balls though U.S. ball is two balls in the case height of 0.15mm or less distortion. In conclusion, the ball of Japanese can be said that 2-seams are higher than Rawlings's balls. The distortion of Japanese ball is less than that of U.S. ball.

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The spin of a pitched baseball affects the ball trajectory which relates to pitchers' performance. We investigated the relationship between the motion of the fingers and the spin rate of pitched baseball. Five professional and three collegiate pitchers participated in this study. The motions of ball, hand and fingers during the ball release were recorded by 3 high-speed video cameras. We defined the amount of angle that the fingers actually rotated the ball as "back spin angle". The ball spin rate was correlated to 1) the amount of extension at PIP joint of the index finger (p<0.05) and the middle finger (p<0.01) and 2) the back spin angle (p<0.01). These results suggest that delaying the ball release is an effective way to increase the ball spin rate, but pitchers are limited to change their timing of the ball release since the timing also determines the projection angle. We concluded that ball spin rate, ball velocity and ball spin axis angle are interrelated with each other under the restriction of throwing the ball into the strike zone.

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Strains of nails before and after ball-release of baseball pitch were measured with strain gauges affixed on nails of 2nd and 3rd fingers. The measurements of strains were executed during simulating ball-release of straight ball, shoot ball and slider ball pitches, and actual pitching. The characteristics of strain of nails before and after ball-release were clarified and the possibility for understanding the state between fingertip and ball was suggested.

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The purpose of this study was to examine the influence of the rolling angular velocity of the bat on batted ball characteristics. In order to construct the model of the bat and ball and to simulate of the ball-bat impact phenomenon, numerical analysis programs based on the three-dimensional finite element method was used. In this study, to focus on the rolling angular velocity of the bat, the simulation was conducted at a constant pitched condition. The rolling angular velocity of the bat was set at 200,1000,1800 [°/s] based on 22 sets of actual measurements taken during a "free batting practice" performed by the member of a collegiate baseball team. The results showed that as the rolling angular velocity of the bat is increased, maximum flight distance does not change, whereas maximum kinetic energy is slightly increased.

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The purpose of this study was to clarify the role of each upper limb and trunk joints to the hitting point height in the baseball T-batting motion through inverse kinetic analysis. Twenty three collegiate male baseball players' motion were captured VICON MX system (12-camera, 250Hz), and kinetic data at each hand were collected by using an instrumented bat equipped with 28 strain gauges (1000Hz). Three heights of hitting point (high, middle, low) were set according to the baseball rules. Kinetic analysis procedures were carried out to estimate joint torques, joint torque powers and works of upper limbs and trunk. From the results obtained in this study, in case of low hitting point, joint torque of flexion-extension axis of shoulder and elbow on bat head side were larger than those of the other hitting points during down swing phase. It was indicated that the role of the head-side upper limb was to adjust the different hitting point. On the other hands, the knob-side upper limb and rotation of torso joint contribute to the acceleration of the bat head during forward swing.

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The fastball's spin rate affects the amount of drop length of pitched baseball. This study examined 1) baseball hitters' accuracy in hitting fastballs with different spin rate and 2) their bat control relating to spatial accuracy during hitting a baseball off a tee and 'imaginary' ball. Thirteen baseball players participated in this study. The first experiment confirmed that the increase in ball spin rate was positively correlated to the increase in the distance from the sweet spot of the bat to the ball. The second experiment confirmed that even experienced baseball hitters could not hit an 'imaginary' ball as accurately as actual baseball on the tee. These findings indicate that hitters' performance can be affected by the fastball's spin rate and it is difficult for them to swing above the actual ball intentionally in order to correct the gap between hitter's spatial cognition and actual ball location.

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The purpose of this study was to investigate the relationship between angular velocity of the bat and movements of upper limbs. Three left-hand hitters performed toss-batting practice. An electromagnetic tracking device was used to record three dimensional kinematic data of the thorax, the humerus and the forearm of the leading side and the bat. The results of this study showed that sequential rotation, in order of the thorax, the humerus, the forearm, was observed for all subject. The subject who recorded the fastest swing angular velocity tended to attain large range of motion in shoulder horizontal abduction and elbow extention. The subject who recorded the fast rolling angular velocity tended to attain large range of motion in shoulder external rotation and forearm supination. These results suggested that sequential motion and the joint range of motion of the leading upper limb might be related to the angular velocity of bat.

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The purpose of this study was to estimate the contributions of the upper limb muscle forces to the generation of racket speed during tennis serve motion. The upper body segments and racket were modeled as a system of 11-rigid linked segments. The sternoclavicular, elbow and wrist joints except the shoulder joint were modeled by a two-axial revolute joint to consider the constraint degree of freedom (DOF) of these joints, and the hand was considered to be connected with the racket via zero DOF virtual joint. Motion dependent term, which shows large contribution in swing motion, was converted into other terms by using the equation of motion expressed in the discrete time system. A recurrent equation with respect to the generalized velocity vector of the system is derived to calculate the contribution of the joint torque terms, external joint force term, and gravity term to the motion dependent term. Then we developed a method to estimate the contribution of the upper limb muscle forces by using the musculoskeletal model consisting of 45 Hill-type muscles with use of SIMM software (MusculoGraphics Inc.). One male tennis player's motion was captured by VICON 612 system (9-cameras, 250Hz). The results obtained in this study shows that muscles in the upper arm, such as biceps brachii and brachialis and deltoid muscles, make significant role in the generation of the racket speed during forward swing motion in tennis serve.

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The requirement of the golf club performance is to hit the ball with distance and accuracy. In addition, the "feeling" for golf swing is a very important performance, but it is very difficult to evaluate the "feeling" quantitatively. In this paper, we investigate the index value which is related to the "feeling" on the golf swing's motion. The golf swing motion is measured by using the motion analysis system at 500 Hz. During the golf swing we analyze swing characteristics. We focus on the club shaft deflection in swing motion and tester's swing speed. The relationship between the analytical result and the "feeling" is investigated. As a result, we showed the close relationship between the quantities of these features and the "feeling" performance.

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The purpose of this study is to examine the influence of the brain shape and structure on the strain distribution by comparing the distribution of the two differently-shaped head physical models in rotational impact. One of the brain model used in this study was shaped actual human brain including the cerebral sulci, gyri and ventricles. The other was simple-shaped model removed those structures. Each model was exposed to angular acceleration by impactor collision causing 4500rad/s^2 peak rotational acceleration with 8ms pulse duration. After rotating 60 degree, two models were decelerated with 1500 rad/s^2 peak, 30ms duration. As the results of experiments, the maximum principal strain at the corpus callosum in real-shaped model was larger than the simple-shaped model. And the concentrations in base of the sulci were also observed in the real-shaped model. Therefore it was clarified that the brain shape such as the cerebral sulci and corpus callosum affect the strain distribution.

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A Three dimentional transparent physical model of a human head with real shape was constructed to visualize and measure relative motion between skull and brain in order to clarify the mechannism of acute subdural hematoma. The model consists of a transparant skul, brain made of syllicone gel, cerebrospinal fluid to reconstruct relative motion between brain and skull and meninges which constraints the motion. The shape was based on real-shaped three dimentional CAD data constructed from CT/MRI images of a specific individual. The results of experiments in the cases of impactor collision to the occipital skull showed that shape of impact force pulse applied to the head was not affected on maximum bridging vein strains because of relative motion between skull and brain due to existance of cerebro spinal fluid.

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Fatal head injuries occur under various impact conditions. In case of direct impact, skull fractures in addition to brain injuries may also happen. To predict head injury with skull fracture, finite element simulation was considered to be more effective. However, existing skull fracture criteria in case of direct impact are not based on strain or stress. So, they can not predict local fractures accurately. Furthermore, it is difficult to conduct experiments on animals in order to obtain stress or strain distribution during fracture. In this study, stress-based skull fracture criterion which can reproduce and predict skull fracture due to direct impact was developed based on the existing skull fracture criterion JHTC, using a finite element head model. This study also shows that a finite element simulation using the developed skull fracture criterion was able to represent possibility of skull fracture during direct impact.

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A boxing is a very traditional and simple sport. You have to make a head injury to an opponent to win the match. But you don't have to make a severe head injury to him. The only thing you need is to get him down in 10 counts to win the game. However, a severe head injury often occurs to boxers and it makes them dead. In this research, Impact simulations were conducted to study an effective blow to a head for a concussion. The blows to a temple, cheek and jaw were applied to the head model in the simulations and the responses were observed. The obtained results showed that the each blows made high stresses to the brain stem, which is the centre of consciousness. The most effective impact is a blow to a temple of a head.

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This paper proposes the motion measurement system and method using inertial sensors. The motion measurement system that consists of 3-axis gyro sensor and 3-axis acceleration sensor measures 3-axis angular velocity and 3-axis acceleration on each body segment. The motion measurement method estimates joint angle using the sensor fusion and the information obtained from inertial sensors. The sensor fusion algorithm with extended Kalman filter can compensate drift error of the gyro sensor using gravity and translation acceleration of the acceleration sensor. The measurement experiment has been implemented to identify the measurement accuracy using the motion measurement system. The result estimated using the proposed method has indicated the joint angle compensated drift error of gyro sensor. The proposed method can estimate the high-precise result, since not only the drift error but also the effect of the translation acceleration are considered. Therefore, the proposed measurement system and method can be used to the motion measurement of various sports.

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This paper proposes the motion measurement system and method of the hand and finger using inertial sensors. This motion measurement system is installed to the forearm, hand and finger. The 3-axis gyro sensor and the 3-axis acceleration sensor are installed on the forearm, and the two 3-axis acceleration sensors are installed on the hand and finger. The motion measurement method decomposes the information obtained from the two 3-axis acceleration sensors installed on the hand and finger to centrifugal acceleration and other acceleration, estimates the joint angle of wrist and finger and the angular velocity of the hand and finger using extended Kalman filter. We have implemented the measurement experiment to identify the measurement accuracy using the motion measurement system and method. The result of the measurement experiment has indicated to the joint angle of the wrist and angular velocity of the hand. The joint angle has avoided the effect of drift error, and the angular velocity has corresponded with value of the gyro sensor. This proposed measurement system and method can apply to the motion measurement of small body segments and sports instruments.

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The objective of this study was to propose walking in water for ACL injury rehabilitation program by simulation. For this Objective, the simulator which can compute the body load considering the fluid force and force acting on the ACL was utilized. The optimal walking forms for three rehabilitation phases were then computed by the simulation. From the simulation analysis, the form for the first phase of the rehabilitation was obtained as "bend the knee all through the swing phase". This form can prevent the ACL from loading the force. The form for the second phase was obtained as "bend the knee greatly and stretch the ankle first, then bend the hip keeping the knee bent and the foot stretched in the swing phase". By this form, the muscles around the knee joint can be trained without loading force on ACL. The form for the last phase was obtained as "keep the thigh backward and the ankle stretched first, then bend the hip joint quickly and greatly in the swing phase". By this form, the muscles around the knee joint can be trained utmost.

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The purpose of this study was to calculate the propulsive force exerted by a forearm in front crawl swimming experimentally. The subject was a male swimmer (height : 1.67m, weight : 61.0kg, age : 23.3yrs, record of 50m Fr. : 26.2sec). The trial was front crawl swimming without kicking in swimming flume, which was set the flowing velocity to 1.2m/s. The pressures on the swimmer's left hand (2 points) and forearm (12 points) were measured during the trial. The attitudes of the left hand and forearm were calculated by movie analysis. The hydrodynamic force exerted by the hand and forearm was estimated. The maximal propulsive force exerted by the forearm was 38.1N and the hand was 81.9N. It was suggested that the forearm would contribute the propulsion in front crawl swimming, although the observed propulsive force exerted by forearm was less than half of propulsive force by hand.

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Badminton shuttlecock is light mass, which is strongly influenced by air resistance and that the wing of the skirt can be easily broken. The highest initial velocity of the shuttlecock exceeds 300km/hr for a professional badminton player. In the present study, the shooting performance of the badminton machine developed by the author is examined. Finite element models of a feather shuttlecock and the badminton machine with two rollers are made, and the shooting simulations proceed with the moving behavior and contact stress of the shuttlecock. The coefficient of friction is examined from the surfaces in contact with the shuttlecock and the roller in the analysis. From the analysis, it is shown that the roller with a small diameter attains the lower speed of the shuttlecock than the other rollers for every shot. The taper angles of the roller edge and the insert height of the shuttlecock are optimized that the shuttlecock speeds are maximized by the shooting simulation and the response surface approach. The validity of the optimum condition is confirmed by the corresponding shot experiments using the two-roller type badminton machine.

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Regarding softball bats made by fiber reinforced plastics (FRP), various products such as single-layer or multiple-layer structures have been developed. In this study, to elucidate the restitution characteristic of the FRP softball bat, the basic characteristics of five types of FRP bats and a metal bat were measured and softball impact tests of each bat were conducted. We investigated the relationship between the bat-ball coefficient of restitution (BBCOR) and the deflection or deformation of the bat and found that the BBCOR of the multiple-layer bat was greater than that of the single-layer bat, and the BBCOR of each bat was influenced by the deformation of bat at the ball impact point.

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In order to analyze the relationship between space-suits knee loading and upright position, we designed and developed orthosis that modeled space-suits knee flexion torque. We captured upright motion with the orthosis and make organoleptic evaluation on ease to keep upright position. To figure out the determination rule of upright position, optimization was conducted under static condition simulation for upright position about each 4 evaluation indices. Comparison of the optimized result with the measured data showed the trend that the knee flexion torque exerted from the orthosis is an important source in making decision of upright position.

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The performance of the baseball helmet with regards to shock-absorption is improved by selecting appropriate shell and liner materials. In this study, we developed a new baseball helmet that offers improved shock-absorption performance and is lightweight owing to carbon fiber reinforced plastics (CFRP) used as the shell material. A baseball impact experiment was conducted by using a hexahedron-shaped headform and flat test specimen, and the CFRP shell material was compared with polycarbonate (PC) and acrylonitrile-butadiene-styrene (ABS) resin shell material. The performance of the helmet was evaluated in terms of external and internal damage of the CFRP shell material, the pressure that acted on the surface of headform, and the acceleration of the current performance standard of baseball helmets. As a result, we found that CFRP helmets were superior in terms of shock-absorption performance while remaining lightweight.

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The purpose of this study is to evaluate the protective capability of the children's helmet to various head shapes by using the FE model of the children's helmet and 1-3-years old child's representative head shapes. Head FE models of various shapes in each age were constructed based on the distribution of head width, head length and head height in Japanese children from one to three years old. Helmet FE model was constructed based on the shape data of existing children's helmet. The analysis simulating a fall from a bicycle was done by using these models. The analytical results showed that the protective capability of a helmet was affected by matching the size to be able to wear the helmet deeply to avoid a force concentration at the contact area of the head.

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The important characteristics to consider when analyzing a baseball bat swing include the centre of gravity, moment of inertia, and the length and mass of the bat. The present study investigated the effects of the mass and centre of gravity of a swung baseball bat. The knob of an experimental bat was equipped with accelerometers to measure the three linear and three angular components of acceleration applied to the bat when swung by trained baseball players. These six components of acceleration were measured using the experimental bat for 25 combinations of mass and centre of gravity. The mass and centre of gravity of the bat were found to affect both linear and angular acceleration during the swing. Thus, bat features relative to individual players must also be considered when analyzing the swing of a baseball bat.

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The purpose of this study is to investigate the hitting performance of the field hockey sticks. First of all, the basic physical properties such as moment of inertia, bending stifiness, stifiness distribution and vibration property were measured in eight selected hockey sticks. Then, hitting test was carried out by using the golf swing robot in order to investigate the maximum hitting point which has close relationship to performance in shooting and passing actions. As a result, some basic and remarkable data of the stick properties were obtained as follows, (1) The moment of inertia depended on mass and center of mass. (2) FRP sticks were staffer than wooden sticks. (3) The node of the first mode was around 160mm from the toe of the stick head. (4) In robot hitting test, the ball speed increased at the point of around 180mm than at the head where most players usually hit the ball.

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The previous paper of the authors made clear the mechanism of top-spin performance in tennis and its improvement by lubrication of strings according to the high speed video analysis. As the main strings stretch and slide side ways more, the ball is given more spin due to restoring force parallel to the string face when the main strings spring back and the ball is released from the strings. Since the notches of strings decrease spin rate, the lubricant materials are effective to the notched strings and the spin rate of newly strung tennis racket without notches is much larger than that of used racket with notches. Furthermore, it showed that the more spin results in the reduction of shock vibrations of the wrist joint during impact. There are several strings now on the market that are designed explicitly to take advantage of the slippery string mechanism for top spin improvement. This paper showed the spin behavior of the ball and the revolutionary flat strings during oblique impact in the laboratory by the high speed video analysis and recognized that flat strings are more slippery and generate more spin than the conventional strings.

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In this study, the authors consider eye movement as a kind of motion skills. Firstly, this paper compares and analyzes eye movement measured from 2 categories, i.e., tennis experts and beginners. The subjects in the both categories are instructed as anticipating "inside-out shot" or "down-the-line shot" from movies of expert tennis players' forehand shot. In order to compare the eye movement between the 2 categories, we make use of a time-series of likelihood distribution from gaze points measured using an eye-tracking device in this paper. We have observed two differences between the experts and beginners as experimental results ; one is that the beginners have more tendency to follow a tennis ball even after the players' shots, and another is that the experts paid more attention to a particular part of the players' body in order to attempt to find any habit as the number of shot increases, while the beginners focused on almost the same point.

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The purpose of this research is to develop the wireless analyzing system for a soccer player by using multiple sensors such as a gyroscope, a GPS and a magnetic sensor. Our proposed system was to capture the kinematic data that were transmitted by Zigbee network for synchronizing all sensors and a real time monitoring. The gyroscope was used to distinguish the soccer player's movements, such as walking, running and stepping in soccer games with a machine learning technique named neural network.

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The vortex structure behind an actual soccer ball in real flight is not clear either in the near-wake or the far-wake, although it is speculated that the vortex structure greatly determines the trajectory and dynamics. We analyzed the vortex shedding characteristics and far-wake structure of a straight soccer ball when slowly spinning (<12.56 rad s^<-1>) in flight under realistic conditions. Two high-speed (1000 fps) video cameras and a smoke-generating agent were used for trajectory tracking and flow visualization, respectively. The cameras were placed midway between where the ball was placed and the soccer goal. The vortex shedding frequency determined from wide-angle images afforded a Strouhal number (St) estimate of about 0.6. The vortex structure behind the soccer ball at supercritical Reynolds numbers (Re) might comprise distorted loop vortices seen behind a smooth sphere at 3.8 × 10^5 < Re < 10^6 (Taneda, 1978). Large-scale undulations were not observed in the vortex trail behind the straight balls once airborne.

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The purpose of this study was to discuss the fluid mechanics acting on a non-spinning and low-spinning flight soccer ball, which called "Knuckling effect ball" or "Knuckleball", using the kick-robot. This robot is driven by high-pressure air in an air cylinder up to 500 kPa, being capable of generating a ball flight up to about 30 m/s. The machine with a size of 1.8m x 2.5m x 2.0m in height can be moved, and be set both inside of a gymnasium and outdoor field. The ball speed can be set between 10 m/s and 30 m/s. Some condition of ball hitting can be adjusted, such as the hitting speed for the ball flight speed, the contact angle between the hitting-board and a ball for the shot angle and the off-axis distance between the normal line to the hitting board and the ball center for the ball spin rate. It is planned to conduct experiments on the knuckle effect of a non-or low-spinning soccer ball. It was determined that the peak of the irregular force in this experiment was about 2.1 N (s.d.=0.4 N). Furthermore, the knuckleball was observed to have an average lift force frequency of approximately 2.0 Hz. It can be concluded that the emergence of irregular forces is one of the characteristics of knuckle balls in soccer.

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It is said that the cause of the swerving ball on no rotating shoot of the soccer ball depends on the outbreak of the vortex occurred in the wake. However, it is not grasped the timing among the vortex outbreak and the swerving of balls. In this study, the velocity fluctuation of the ball wake was measured with hot wire probe and the oscillation of the ball was measured with three components load cell. Those experimental results were analyzed by wavelet transform and a relations among the velocity fluctuation and the fluid forces was grasped experimentally.

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The mechanism of less spinning soccer ball has been analyzed by the wind tunnel experiment. Used at the large wind tunnel to observe the two longitudinal vortices behind a soccer ball. These two vortices are equivalent to the tip vortex of the aircraft. FIFA World cup South Africa matches were held at 1500m altitude where air density is low. The displacements are calculated with tunnel wind experimental data, compared the distance of the soccer ball flight distance by a difference of the air density of the sea level 0m and 1,500m. The soccer ball flights by 1 meter long in the X direction.

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Recently, accuracy of the infront kick (the ankle is in an "L" shape and turned out at a 45o angle and contact is with the side of the instep), which has greatly influenced the success or failure of set play, has garnered increased importance in soccer. The aim of the present study was to examine the accuracy of the infront kick by analyzing the conditions, such as angle and velocity of kick, preceding the kick and the ball's resulting trajectory. Subjects were 7 male players who belonged to a university soccer club. Using the infront kick, they were required to hit each of 4 targets set up at different distances behind a screen positioned 9.15 m in front of the kicker. The behavior of the ball was recorded from the rear by two normal-speed video cameras and analyzed using the three-dimensional direct linear transformation method. Another video camera was placed facing the kicker to capture variables related to ball rotation. Results revealed that displacement of the ball from the center point of each target occurred in an oval distribution on a diagonal axis from top-right to bottom-left, though the axis inclination was different for each player. Moreover, the ball trajectory was affected by the initial direction and velocity of the ball just after being kicked and by the rotation of the ball and the inclination of its rotation axis. It was thought that by mapping each player according to their own kicking strategy, values for hitting the target could be determined.

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The purpose of study was to reveal the interaction during ball impact phase of soccer kicking in female soccer player. Fifteen female and male soccer player performed maximal instep kicks. The behavior of kicking foot and ball during ball impact was captured two or three dimensionally by the high-speed cameras at 1,000fps. Foot velocity, ball velocity, and coefficients of restitution (COR) were calculated to evaluate the fundamental characteristics of kicks. The average ball velocity for female players was 22.8±2.7 m/s. The average ball velocity for male players was 27.4±2.2 m/s. The average foot velocity for female players was 17.6±1.2 m/s. The average foot velocity for male players was 19.8±1.4 m/s. The average ball and foot velocities were lower for female players than for male players, and the differences were statistically significant (p < .05). Thus, The impact point was calculated as the distance from the center of mass of the foot to the contact point. Impact on the surrounding area of the center of mass the foot produced the greatest coefficient restitution. The correlation coefficient of the distance from the center of mass of the foot to the contact point and COR for female players was -0.50, for male players was -0.68.

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The aim of this study was to clarify the lower limb motion involved in kicking a futsal ball using by the three-dimensional technique. The results show that the kicking performance of professional futsal players was as good as that of professional soccer players. On comparing our results with those of previous studies, we observed that the maximum-effort motion involved in kicking the futsal ball had the characteristics of both instep kicking and side-foot kicking, as seen in soccer players. Futsal coaches training players for powerful kicking should advise the players to use a combination of soccer-style instep kicking and futsal-style side-foot kicking.

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The objective of this study was to construct finite element models of the simplified foot and soccer ball to simulate the ball behavior in curve kick. A 3D finite element model of the foot was developed using the barefoot and footwear shapes, which were obtained from a 3D laser scanner. A finite element model of the ball consisted of composite shell elements that include a hyperelastic model to define the latex bladder layer and a linearly elastic model to define the outer panels. Five experienced male university soccer players performed curve kicks. The kicking motions were captured three-dimensionally by two high-speed cameras at 2,500 fps. The models were validated by comparing the results of the finite element analysis to those of the experiment. The finite element results of the ball behavior during and immediately after impact were in generally good agreement with experimental ones. The models showed the ability to represent the ball behavior at ball impact.

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The purpose of this study was to describe the time-course of change in the orientation of the longitudinal axis of the runner's body passing through the center of mass (CM) during the maximum-effort sprinting on a curved runway. Ten male collegiate sprinters were asked to sprint along the 2nd lane on an official 400m track. The performances were recorded with four high speed cameras. The DLT algorithm was used for 3D reconstruction and the longitudinal axis of the whole body passing through the CM was calculated. The results showed that the longitudinal axis of the whole body maintained a forward (5.8±1.9°) and inward (14.1±2.2°) leaning-position during the entire stride cycle. The orientation, however, fluctuated during the stride cycle; the longitudinal axis leaned toward inward direction by 3.6±0.7° during right contact phase and toward outward direction by 2.8±0.6° during left foot contact phase. These results indicate that the ground reaction force exerted on the body during each contact phase generated rotational motion about the antero-posterior axis in the opposite direction in curved sprinting.

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The purpose of this study was to quantify the functional role of support leg joints including MP joint of the leg during running motion. The whole-body was modeled as a system of 16-rigid linked segments, and MP joint torque was estimated with sole pressure information. The equation of whole-body motion was derived considering constraint axes of joints such as inversion/eversion axes of the elbow and knee joints. The dynamic contributions of the support leg joint torques to the generation of whole-body CG's acceleration were calculated for two subjects with different foot contact pattern, such as rear-foot strike and fore-foot strike, under different running velocity conditions. The results in this study indicate that 1) planter/dorsal flexion torque of ankle joint is great contributor to the generation of horizontal and vertical components of body CG's acceleration, 2) abduction/adduction and internal/external rotation torques of hip joint contribute to the accelerations for rear-foot striker, and 3) planter/dorsal flexion torque of MP joint is small contributor and shows inverse pattern with respect to the contribution of planter/dorsal flexion torque of ankle joint.

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The purpose of this study was to clarify the influence of arm swing on jumping performance and jumping motion of lower extremities in vertical jumping. Fourteen healthy male subjects performed two types of vertical jumping with and without arm swing from a squatting position forcefully. During jumping, the positions of eleven body's landmarks attached reflective markers were recorded at 250 Hz using ten motion analysis cameras and the ground reaction forces of each subject's leg were measured with two force plates. Kinematic and kinetic data were calculated. Also, the vertical acceleration of whole body and five body segments of head-trunk, thigh, shank, foot and arm were calculated with the Feltner's algorism. Our data suggested as follows; with arm swing during jumping, 1) the vertical acceleration of whole body was increased and one of thigh contributed to accelerate whole body, 2) the vertical acceleration of head-trunk was inhibited in the middle of jumping motion, and 3) the extension torques of the ankle and the hip joint were increased. It was speculated that the activities of the femoral extensors acted on jumping motion effectively.

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