Advances in technology today have influenced and changed many aspects of our lives. As technology becomes smaller it is able to be used in more and more aspects of our daily lives, competitive and recreational sports are no exception. Borrowing from many disciplines athletes today are clad in space age clothing, ride aerospace and automobile inspired bicycles and use high tech racquets built from composite and other 'high tech' materials. Often accompanying each athlete today are complex watches and heart rate monitors that just a few years ago were the province of only our elite sports academies and athletes. As we enter the age of wireless communications pervading our everyday lives and an unquenchable thirst for information, the dream of small unobtrusive monitoring devices that can quantify every aspect of an athlete's performance in real time is becoming a reality. One day athletes will no longer need to go to specialist laboratories for performance assessment but instead wear widely available devices during everyday training and perhaps even in competition. This paper outlines some of the recent developments in monitoring technologies and the implementation of wireless solutions. Aspects such as human comfort, power consumption, antenna design, choice of frequency band and some examples will be discussed.
Generally muscle fatigue has been defined by changes of motor units as the integrated function signals of the never and the muscle as impulse signals of electromyogram. The purpose of this study was designed to evaluate with the wave signals of the recruitment pattern of the relative motor unit during maximum voluntary muscular contraction and three stepwise running speed of (40%, 60%, 80%, maximum speed record of 1500m) by the surface electromyobram (SEMG) spectra, non-invasivery. SEMG of the Rectus Femoris and the Biceps Femoris were processed for SEMG to be calculated power spectra with the time series analysis of Max Entropy Method Calculation (MemCalc) gradient at the sampling rate of 1 msec. Total Power Spectrum (area, TPS), and the decreasing gradient (β coefficient) of 1/f^β nonlinear equation in the waves of SEMG spectra were applied for SEMG spectrum to evaluated with muscle fatigue.
In motion analysis, the optical method is often used, but non-optical method is not so. The purpose of this study was to attempt three-dimensional motion analysis using electromagnetic tracking device, which is one of the non-optical method. First we defined body coordinate systems by attaching sensors to each segment. Then we calculated joint angles by adapting the relative movement of two coordinate systems to joint motion. The angle of lumber, hip and knee was compared between two different kick motions. As a result, we could concisely obtain many kinds of joint angle, and these data clarified the difference in two motions. The present study suggests that this experimental method is useful to analyze body motion.
The purpose of this study was to quantify the contribution of the joint torques of human whole body to the vertical velocity of the center of gravity (c.g.) of body during jumping motion. The human body was modeled as a system of fifteen rigid segments connected with a simple ball joint. The foot was considered to be connected with the center of pressure (C.P.) on the ground by a virtual joint. The equation of motion with respect to whole body was obtained from the equation of motion for each segment and equations for constraint condition in which adjacent segments are connected by joint. The contribution of the joint torques to the vertical velocity of body's c.g. was derived from the dynamic equation of body. The contribution consisted of three parts, such as ; total joint torque term ; motion dependent term ; and gravitational term. The total joint torque term was, furthermore, divided into each joint axial torque term. A subject performed a jumping motion with single support leg in the support phase. The motion was captured with VICON motion system, and the ground reaction forces were measured with two force platforms. From the results, the order of the contribution to vertical velocity of body's c.g. makes the transition from proximal to distal joint of the support leg in the support phase of the jumping motion.
This paper describes a new method to measure and analyze three-dimensional rotation and translation analysis of upper limb in basketball shot form. In general, the shot form is measured by taking the photograph of motion with the high-speed camera and/or video camera and analyzing the photograph with direct linear transformation method (DLT method). The suggesting measurement method was derived by the kinematic human body model analysis. The measurement system developed by using the three dimensional rate gyro sensors set at the several body positions can measure the three dimensional rotations and the three dimensional translations of various parts of body. By using this system, the motion of a thin part such as wrists and ankles can be measured easily. In addition, this system can measure the basketball shot forms of various players correctly.
In this study, impact force measurements and biomechanical analysis were carried out during the TSUKI (Punching) of SHORINJI-KEMPO. The impact force and kinetic parameters were measured by using strain gages and the three-dimension rate gyro sensor. Furthermore, the force of pivot foot was measured by a 6 degree-of-freedom force sensor. The trained SHORINJI-KEMPO players showed the larger impact force in contrast to that for the un-trained player. It is important to increase the impact force that the player supports the body with the toe side and the inside of the pivot foot when the player starts the punching motion.
The purpose of this study was to evaluate the canoe paddling on the flat water racing during a canoe race. It was provide the paddle install four accelerometers to measure the acceleration applied to the paddle. Experiment was done with subjects rowing 500m at the race speed and measuring acceleration of paddle and showed the following results. (1) The change of acceleration by each paddling showed same results for each subjects. On the other hand, each subjects paddling were different and showed unique change. (2) The time of one cycle of paddling got longer during the race and this showed paddling motion gradually got slower. (3) Liner acceleration didn't change much throughout a race. But angular acceleration decreased throughout a race. These resulted that paddling motion to liner direction changed less but rotary motion of paddling changed small throughout a race.
In ice hockey shooting motion, it is impossible to determine the forces and moments acting on the hockey stick with the only visual information about motion of the stick, because the upper extremities and the stick form a closed multiple-segment loop. In this paper, an instrumented hockey stick equipped with twelve-pair of strain gauges was proposed to reduce the difficulties. A calibration method for the stick was proposed additionally. The strain sensors provided force or moment information, such as 1) torsional moment acting about longitudinal axis of the shaft, 2) bending moments at each sensor position, and 3) tensile and compressive axial forces. Unique solution of forces and moments exerted by each hand was achieved through force and moment equilibrium conditions using the strain information. From the calibration results, the longitudinal axial force have small influence on the coefficients of strain gauge sensors for bending moments.
The purpose of this study was to clarify a role of pelvic twist in trunk rotation movement during asymmetric lifting tasks when varying posture of the lower extremity joints. The effects of external rotation of the right foot on pelvic twist and trunk rotation movement were examined from the viewpoint of kinematics data. Six healthy male subjects performed asymmetrical lifting tasks with 12kg loads on three external rotation angles of the right foot that were 0, 30 and 60 degrees. During the lifting tasks, the 3D loci of the anatomical landmarks attached 30 reflective markers were recorded at 120Hz using ten motion analysis cameras, and Euler angles of eight body segments were calculated by the rigid body link segment model. The relationships between pelvic twist and trunk rotation, and hip joint rotation were discussed. These data showed as follows ; with increasing external rotation angle of the right foot, 1) the right hip joint rotated externally, 2) the ratio of pelvic twist to the maximum rotation angle of the trunk was increased and pelvic twist contributed to rotate the trunk, and 3) at the maximum rotation of the trunk, internal rotation angle of the right hip joint decreased. This suggested that for asymmetric lifting tasks external rotation posture of the lower extremity contributed to reduce loads on the low back and internal rotator of the hip joint.
The purpose of this study was to investigate the concept design of the education system for the anti-doping using the e-learning lectures introducing the bio-chemical, statistics and law simulations. The platform of the e-learning system was set on the e-learning center at Nagaoka University of Technology. The e-learning lecture could be transmitted from this platform to the computer terminal around the world, Every-one could receive and take the e-learning lecture using own personal computer in every time and at everywhere. To have a good effect, the e-learning lecture for the anti-doping introduced the 3 simulations as follows ; the bio-chemical simulation (BSim), the statistics simulation (SSim) and the law simulation (LSim). The BSim educated mainly about the side effects of the doping, especially the drug (medicine) doping. The SSim instructed the disadvantage of the doping from point of the low of the doping benefit. Furthermore, LSim instructed the illegality of the doping, especially from the point of new law established by the point of the criminal law. The subject for this program would mainly be a pupil in a junior high school and a student in a high school.
To clarify the factors effecting aerobic (VO2max) and anaerobic (Pmax) power output in humans, we analyze the cross-sectional relationship between VO2max, load at VO2max, Pmax, load (P-load) or speed (P-speed) at Pmax, and lean body mass (LBM) in triathlon (TA) and American football (AFB) athletes, and control subjects (CON) during maximal cycling. VO2max and Pmax were greater in TA and AFB than in CON, and a significant correlation between VO2max and Pmax was found in CON, but not in TA and AFB. LBM was significantly correlated with Pmax or P-Load in all groups, and also correlated with VO2max in TA and AFB but not in CON. In AFB, a significant correlation between P-speed and Pmax was found. These results suggest that 1) increased LBM enhances maximal anaerobic and anaerobic power in trained athletes, 2) in untrained subjects, aerobic power is related with anaerobic power but not with LBM, 3) increased LBM is related with muscular power or speed in high power athletes. Thus, different factors affect aerobic and anaerobic power output between AFB, TA and CON.
To evaluate the effect of Binding Pedals (BP) on cycling exercise, we investigated the differences in leg muscle activity and mechanical efficiency between BP and Normal Pedal (NP) by measuring electromyogram (EMG) and energy expenditure during cycle exercise. Seven non-cyclists and five cyclists were performed 5-min cycling exercise under nine conditions, at three cadences (50, 75, 100rpm) and three intensities (75, 100, 150w), wearing BP or NP. BP did not increase ⊿efficiency, calculated as the ratio of increment in the external mechanical power output to the increase in metabolic energy expenditure, in short-term exercise. In the case of cyclist, BP increased vastus lateralis (VL) activity and decreased gastrocnemius lateralhead (GL) activity. In the case of non-cyclist, however, wearing BP increased GL activity and decreased Tibilis Anterior (TA) activity. Thus, there are different effects of wearing BP on the EMG activity pattern between non-cyclists and cyclists.
"Easy to move" is one of the most important functions for apparels, especially for the sportswear. Skin strain is one of the factors to provide for this "Easy to move". The purpose of this study is establishment of the polygon strain analysis technique on 3D-CG and application to the skin strain simulation. We derived an analytical technique of the polygon strain using the idea of the minute strain of elastic material. We constructed 3D-CG model that imitate the human body, and made posture that knee was flexed, hip was flexed or hip was extended. We calculated the polygon strain using this model and compared with the skin strain measured on the human body. There is a significant correlation between the polygon and the skin strain (r=0.972, p<0.01). This result suggests that skin strain simulation is effective to the quantification of the skin strain that is important to design the sportswear.
For the driving skill improvement, the superior body size or the muscular strength is not dominant, but the native equilibrium maintenance ability should be important. In this paper, the correlations between the driving skill improvement and the fall index (FI) were inspected. The driving skill improvement was defined as the difference of time to go around a racing car circuit. The single-seat, open-wheel formula car formulated in 2006 Formula SAE[○!R] was made by Kanazawa Univ. Formula R & D and was used for the test car. The training with a driving simulator was practiced to discriminate the FI. As the results, the average times to go around a circuit approximated to almost same in this training duration when the FI was same.
The purpose of this study is to discuss the aerodynamic characteristics of soccer ball using computer fluid dynamics (CFD). An incompressible unsteady analysis was performed using the finite volume method based on fully unstructured meshes with a commercial CFD code (FLUENT6.2, Fluent Inc.). The turbulent model of this study was Large Eddy Simulation (LES) model. The drag coefficient of non-spinning soccer ball in CFD was approximately 0.19 and that of wind tunnel test was about 0.15. It was observed that the large scale fluctuation was generated in the lift coefficient. The coefficient of moment was almost 0. The separation point of the non-spinning soccer ball in CFD retreated to〜120°from the front-stagnation point and the vortex region shrank when the supercritical ball velocity was 25m/s. In CFD analysis using LES, the complex vortex structure was observed near the ball model. However, it was difficult to represent the vortex structure in a little away from the ball.
This paper describes the influence of a supporting system on aerodynamic coefficients of a soccer ball. An official soccer ball in World cup 2006 (or a smooth sphere) is supported by two methods in the test section of a wind tunnel. One is the strut from the behind, and the other is piano wire. The results are summarized as follows: The critical Reynolds number is defined more clearly by the strut system. The deviation of the side force coefficient is less than 0.1 for both systems. The lift coefficient fluctuats against the Reynolds number for both supporting system, especially for the piano wire system.
The purpose of this study is to analyze the interaction of foot joint and the ball at instep kicking by different impact point using the high speed video camera (4,500fps). Moreover, we analyzed the kinematics on ball kicking with shoe and without shoe condition. It is tendency that the swing speed before impact of toe point is larger than that of near ankle joint. The ball speed after impact of the far points were smaller than that of the near and the middle points. In the case with shoe, both swing speeds and the ball speeds indicate a low value compared with the case without shoe. In the case with shoe, the mean of repulsion rate of NIP was 1.30, that of MIP was 1.17 and that of FIP was 1.16. In the case of without shoe, the mean of repulsion rate of NIP was 1.51, that of MIP was 1.41 and that of FIP was 1.22. It is considered that the energy loss of the material of a shoe surface is one of the important factors for increasing ball speed.
A slipstream is formed behind an object in downstream. Even in a marathon event, it is possible to use preceding runners as a shield to reduce aerodynamic drag and to carry out physical strength preservation. These preceding runners are called pacemakers, who maintain a lap time of an objected runner. In this research, to confirm the effect of pacemakers' slipstream and their formations, experiments and numerical calculations were carried out in a real Reynolds number and compared with experiments concerning drag and flow field.
A ski jumping flight analysis was attempted on the basis of the high-speed digital video image taken at Hakuba Ski Jumping Stadium in Japan. Initial 40m of flights of 120-m jumping after take-off were recorded by a fixed high-speed video camera at a frame rate of 250 frames/s. After some corrections, a number of time series data were extracted for the loci of key parts of a jumper such as the waist, the ski boots and the ski tip as well as for key angles representing a jumper posture such as the ski angle and the forward leaning (ski-body) angle. The primary purpose of the present study is to derive the aerodynamic force data during real jumping flights, in particular in the early phase of a flight.
It is known that the presence of a soft stiffness between a baseball and a bat such as the radial compliance of the barrel region of the hollow bat increases the COR. In order to make use of this effect in the case of a rubber-ball baseball, it is obliged to attach a soft material over the barrel actively. Using 3-dimensional finite element analysis system for the impact between the rubber ball and the bat developed by authors, for the bat whose barrel is covered with a sheet of the soft material the effects of Young's modulus, thickness, Poisson's ratio and etc. on the COR are investigated. It is found that a thick material which has the low values of Young's modulus and Poisson's ratio is effective to increase the COR.
The purpose of this study was to investigate the effect of the mass and the position of center of gravity of a baseball bat on its hitting performance. Twelve skilled baseball players were used in the study. A bat was developed for which the mass and position of center of gravity could be adjusted. In this experiment nine different settings for the position of the center of gravity and the mass were used. The motion of the bat during swings was analyzed by the DLT method using two cameras, and three-dimensional kinematic data were calculated for the impact with the ball and during the hitting process. The main results are summarized as follows: 1) For all the baseball players, the head velocity of the bat at impact was large, so that the position of the bat's center of gravity was near to the grip. 2) For all the baseball players, the bat mass did not affect the head velocity of the bat at impact. 3) For all the baseball players, a significant negative correlation was found between the moment of inertia about the grip circumference of the bat and the head velocity at impact. 4) In one case, the mass of the bat had a significant influence on the angular velocity on impact for a player that had a translational swing. In this case, the characteristic of the swing type was shown to result in different hitting performances. When choosing a suitable bat for each player, the critical factor is the swing style of the player, which could be gauged from the mass and the position of the center of gravity of the bat. This finding suggests that the moment of inertia of the bat's circumference could be used as an index.
Recently, baseball bats that have kinds of characters have been marketed due to advances in the materials and structure of modern baseball bats. One of remarkable point is a sweet spot in bats. But a sweet spot is sensuous and its point is laxness. So the reason why a sweet spot is approved is researched in this study. First of all, the first node, the second node and center of impact were measured. Next, the ball was made to collide with them and the repulsion coefficients were measured, and compared.
The roles of the upper extremities during baseball batting motion are transfer of the energy generated by the lower extremities into a bat and control the bat to place in a hitting point. Since the bat is manipulated by both hands in swing motion, the upper extremities and the bat make a closed multi-segment loop. It is therefore impossible to determine the forces and moments acting on the bat by each hand with only visual information of motion of the bat. The purpose of this study was to investigate three dimensional kinetics of each joint in the upper and lower limbs by using 1) an instrumented baseball bat to measure forces and moments exerted on the grip handle of the bat, and 2) two force platforms to measure ground reaction force and moment exerted on each leg. Two collegiate baseball players participated in the experiments. The positions of marker of the body segment endpoints and the bat were captured with VICON motion analysis system operating at 250Hz. Kinetic analysis of joints were realized with inverse dynamic solution with the data obtained by the instrumented bat and the force platforms. The kinetic results such as joint torques and joint torque powers indicated the roles of each upper limb and each lower limb during baseball batting motion.
A helmet of a baseball player is important protective gear to prevent a head injury when hit by a pitch. Although the impact performance of a helmet has been evaluated, the change in its impact performance when hit again has not yet been considered. This is because once a helmet receives a big impact, it is not re-used even if there is no visible damage to its surface. However, if the damage is not visible, there is a possibility that the same helmet is re-used. In this study, a baseball ball launcher was built, and a repeat impact experiment with a helmet put on the head model and a ball was conducted. The effect of the number of impact times on the acceleration which acts in the head model was considered.
A pitching machine of roller type for baseball achieves easily variable balls. On an official hard-baseball, having a seam, it is observed to affect variations in the ball's spin revolutions and the projected angle. In this study, a dynamic behavior and a contact stress state of the pitched ball with the baseball machine of roller type is analyzed using the commercial dynamic finite element code (ANSYS/LS-DYNA). In addition, their analysis results (provided the ball's speed and spin revolutions) were given as an initial condition, and the drag and lift force of a ball were analyzed by the computational fluid dynamics software (ANSYS/CFX). From these results, the trajectory of the ball for each posture was calculated. An effect of the throw accuracy by the ball with a seam was considered.
Practicing throwing of American football is effective in improving the throwing motion of baseball, thus, enhancing the pitching performance. It is however unclear how throwing of American football is related to that of baseball in terms of body control. For our investigation, we employed three subjects. Of these three subjects, one person has some experience with baseball and the other two are almost new to baseball ; they could only throw and catch a ball with others. We asked the subjects to practice throwing balls of American football and baseball for one month and collected data concerning their pitching forms and the speed of balls using a high speed video camera and a speed gun. We found as the result that only one student who has some experience with baseball improved his throwing form and increased the speed of the ball.
Engineering technology has advanced to enable manufacturers to discover and synthesize new materials and new design with sport equipment. There are rackets of all compositions, sizes, weights, shapes and string tension. At the current stage, very specific designs are targeted to match the physical and technical levels of each user. However, ball and racket impact in tennis is an instantaneous phenomenon creating vibrations and large deformations of ball/strings in the racket. The problem is further complicated by the involvement of humans in the actual strokes. Therefore, there are many unknown factors involved in the mechanisms explaining how the specifications and physical properties of the high-tech rackets influence the racket capabilities. This study investigated the physical properties of various high-tech rackets, predicting racket performance in terms of the coefficient of restitution, the rebound power coefficient and the post-impact ball velocity. The coefficient of restitution e_r (COR) can be derived considering the energy loss E_1 due to racket vibrations and E_2 due to large deformations of a ball and strings corresponding to the coefficient e_<BG>. It is based on the experimental identification of the racket dynamics and the approximate nonlinear impact analysis with a simple forehand swing model. Furthermore, it studied the effect of racket frame in-plane hoop vibrations on the coefficient of restitution and the energy losses in tennis rackets, which has been left unknowns for a long time.
The record of pole vaulting has progressed rapidly by the appearance of flexible fiberglass pole. In analysis of the dynamics of the pole vaulting, it is necessary to consider a high flexibility of pole and each joint torque of body. In this research, simulation analysis to optimize the joint torque was done by using Genetic Algorithm. It is introduced a combination system consisted of a flexible pole and seven link (vaulter). From the results, it has been observed that the optimized torque have the tendency.
It is important to improve the initial launch conditions of golf ball at impact between golf club and ball for longer distance. Here, the initial launch conditions of golf ball mean ball speed, launch angle and back spin rate. It is also important to analyze the mechanism of ball spin to improve the initial conditions of golf ball. In 1980's we proposed the concept of impedance matching to design the high C.O.R. (Coefficient of Restitution) golf club, that is, the frequency at the minimal value of mechanical impedance of golf club head and ball should be equal to maximize the C.O.R. In this paper the influence of the natural frequency of golf club head and ball on ball spin is investigated to analyze the mechanism of impact. For this purpose the contact force and the contact time at the impact between golf club head and ball are considered from Finite Element Analysis.
This paper describes the method of estimation of the restitution characteristics of golf clubs by calculation of energy transmission ratio with modal analysis. The club head was analyzed by FEM method, the ball was modeled by two masses connected by a spring and the contact was modeled by a non-linear spring and a non-linear damper. The relationship between the restitution characteristics of club head and the impact point became clear. The effects on the shape of club head on the restitution were also investigated.
This paper considers the evaluation of jerk to design the shaft of a golf club. The jerk, the derivative of acceleration, is more sensitive and useful value. We think that the reduction of jerk means good feeling and reduction of power-loss during golf swing. The result of experiments shows that the jerk is available as a dynamic characteristic of golf club. The experiments were done with two golf clubs that the static characteristic is almost same, but the shaft has only difference fiber-allocation. We couldn't find the golf clubs' difference through the impulse hammering experiment of frequency response function, but we could find a little bit different behavior through the step excitation jerk frequency transfer function.
This sheet deals with the spin characteristics of the oblique impact system, which is composed of the golf ball and flat surface. The impact system is modeled by both a nonlinear spring and a nonlinear dashpot using Hertz's contact theory. This model is applied to the oblique impact system of golf ball. The spin characteristics of golf ball were obtained by using this model. The results show that the spin rate increased in proportion to the angle of incidence and impact velocity. Also, in the case of increase the tangential stiffness, the spin rate was decreased and the angel of reflection was increased.
The inward pull motion at the impact stage of the golf swing, commonly observed with expert players, is investigated in this paper. It is shown that the acceleration occurred by the mutual action of the two governing factors of the system, the centripetal force and the pull velocity. The phenomenon is to be called the parametric acceleration, following the parametric excitation of vibration problems that are governed by the similar equation. Based on the fact, a swing model consists of two links and one linear actuator is constructed on the Working Model Simulator. The result simulates accurately the swing of the expert professional golfer.
By the standard, the discrimination of golf club can not be attempted concerning the flight-distance, today. Then, the movement which intends to raise the value of golf club in feeling of the batting sound is noticed. In this study, we made batting sound prediction program for the purpose of predicting the batting sound by design stage for attempting cost reduction in product development. In this paper, we describe the result of the practicability of the program which using the titanium tube equal to the driver.
The purpose of this study is to investigate the influence of impact conditions on the rebound behaviour of a golf ball after impact, by conducting a finite-element (FE) analysis of a ball colliding with an imitation golf clubhead. The imitation clubheads were designed based upon the mass, volume and position of the centre of gravity of commercial clubheads. 4 circular hollow bodies of constant mass, made of a titanium alloy, with increasing loft angle were manufactured. This was made possible by changing the thickness of the back face. Both an FE model of a ball (with hyperelasticity and viscoelasticity) and an FE model of a clubhead (with linear elasticity) were constructed. The impact behaviour of the ball and clubheads was obtained from the impact simulations using these models. Impact experiments were also conducted to confirm the accuracy of the FE models, by comparing the results for the experiments to those for the FE analyses. The results of the impact simulations matched with the experimental results. The impact behaviours were analysed by varying the impact point of the balls colliding with the clubheads (using the FE models). The impact point where the rebound velocity of the ball was the largest, was located below the sweet spot (sole side of clubhead), and this impact point depended on both the position of the sweet spot and the loft angle of clubhead.
This paper proposes an evaluation method of distribution of shaft flexibility of golf club by real swing. Head speed of the club, stability of direction of a ball, reliability of impact at the sweet spot and feeling of the club under the swing are used for the evaluation. First, difference of swing by three types of distribution of shaft flexibility is discussed for high and middle beginner level golfers. Next, stability of direction and reliability of impact at the sweet spot are measured and these mean values and distributions are obtained. Questionnaire of feeling of the club of swing are performed and these data are statically analyzed and obtained principal component and coefficient of correlation of each item. From these data, the best distribution of shaft flexibility of golf club is evaluated by evaluation function which would be decided by players requirement.
"A pendulum stroke" is used by many golfers. The purpose of this study was to understand human motor control by comparing human putting movements and the physical pendulum of firmly fixed putter. Three experienced professional golfers participated in this study. They executed ten putts as accurately as possible, in order to reach a target distance of 2, 4, 6, 8, 10m. Movement pattern characteristics were assessed by kinematic analysis. In addition, putts of the same distance were tried using the physics pendulum. It was found that the putter head speed, at the time of impact in the physics pendulum putt, exceeded that for humans. On the other hand, for ball speed after impact, the human's putting was faster than that of the physics pendulum's. The difference between human putting and the physics pendulum was shown. However, it was understood that successful putts are achieved by having skillful motor control.
The purpose of this study was to investigate the differences of the motion and muscle activity between skilled and unskilled subjects during sharpening kitchen knife. Two skilled subjects and one subject with no experience of sharpening a knife were asked. Their motions were recorded by 4 cameras (60Hz) and surface EMGs were recorded from 4 muscles of both upper limbs. The skilled subjects had shorter motion duration, longer motion pathway, and higher reproducibility in each stroke than the unskilled subject. In each stroke prominent EMG activities in extensor carpi ulnaris, triceps brachii, and deltoid muscle were observed in the skilled subjects. We also examined the shape of the sharpened knife blade of each subjects closely under a microscope. The front edge and central region of the knife sharpened by the skilled subjects changed odd-shaped, while those by the unskilled subject remained unchanged.
We investigated the process in which a person acquires a skill for sharpening a kitchen knife for three weeks. We applied a motion capture (60Hz) device and 8-ch electromyography to measure bodily movement of the subject and four muscles' activities of both upper limbs. Data were collected on immediately after the first training, the following day, 1 and 3 weeks later. As his experience enlarges, motion duration during each stroke became shorter, while reproducibility of motion duration and motion pathway in each stroke became lower. Additionally, EMG activities in extensor carpi ulnaris, triceps brachii, and deltoid muscle turned to be prominent while EMG activity of biceps brachii disappeared. We also examined the shape of the sharpened knife blade. The front edge and central region of the knife sharpened only on 3 weeks later changed from straight into odd-shaped.
We propose a new method of analyzing perturbation on phase of human motion. We have examined periodic movement of knife grinding as an example of skillful motion. In periodic movement, we can obtain a return map on phase of kinematical parameters. The return map can visualize the change of phase shift at every cycle. As a result, experts and novices had different convergent pattern. We defined it Phase Convergence. Their return maps show unique pattern which depends on subject's skill or task and so on. It is reasonable to suppose that the perturbation is caused by interference of the phases.
The aim of this study was to clarify a knack for skillful winding operation by a professional of braiding. We recorded kinematic and electromyographic (EMG) data simultaneously using three high-speed cameras (125Hz) and a 6-channnel surface EMG system. EMG activity was recorded from selected superficial muscles of the left upper limb-flexor carpi radialis, extensor digitrum, flexor carpi ulnaris, extensor carpi radialis, biceps brachii, and triceps brachii muscles. Kinematic characteristics of motion of the left upper limb were identified by wrist (palmar) flexion-extension, ulnar-radial flexion, pronation-supination of the forearm, and elbow flexion-extension. Compared to the parallel-winding method in which limb movement was very slowly at elbow and wrist joints, in the cross-winding method each joint moved repeatedly with short quick steps. In addition, whereas EMG activity of each muscle in the parallel-winding method was little, in the cross-winding method EMG burst of the biceps and triceps brachii appeared alternately, and the pattern of EMG burst of the BB and TB matched those of the kinematic characteristics. These results indicate that controlling the proximal muscles appears to be important for the skillful cross-winding method.
In this paper, we measured movement of horse's hip top and displacement of various part of the rider. Jar (up and down motion) during trotting was measured, relation to the rider's motion. The judge's evaluation was clarified with the amount of displacement of the horse. First, the general rider has the heel in a position that is lower than the junior rider. This showed that sticking of jockey's leg and horse's body was good. Next, an advanced score concerning the comprehensive evaluation of the screening criterion lowers when the movement of horse's hips in the top part is small. This showed becoming the demerit mark by each movement subject.