Medical care providers, social services, and legal systems are needed to make critical decisions regarding child abuse however the diagnosis is difficult because the differential diagnosrelys on individualized experiences, and empirical data. Especially, although, subdural hematoma is one of the commonest features of the abused children, the mechanism is unknown. We constructed an infant anthropometric dummy that had a realistically shaped physical model of an infant head to help visualize and clarify the mechanism of acute subudural hematoma during shaking or falling accident. Intracranial brain motion during shaking was more significant than the case in falling because significant reverse rotational motion between the skull and brain occured during shaking. Therefore, the risk of acute subudural hematoma in shaking was significantly higher than the falling situation.

View full abstract

Nihon University and Nippon Medical School conduct the traffic accident investigation of actual conditions of a car with a core of the hospital, and are investigating a physiological damage, anatomical damage and the vehicle damage. We describe the result of having examined the relationship between physiological index and anatomical index.

View full abstract

This study aim to control automotive using biosignals reacted before drivers step on the brake pedal in traffic accidents occurrence. We measured reaction time and electromyogram from lower extremity of middle-aged generation. Electromyogram measure using lower extremity muscular group for pedal operating analysis, included tibialis anterior, rectus femoris, peroneus longus and vastus medialis. The experimental results showed a superior response to change, regardless of the tibialis anterior pedal.Electromyogram of tibialis anterior was reacted at the moment of releasing the accelerator, regardless of age.

View full abstract

In this study, the model which can calculate the velocity at seat-off in success to assist the sit-to-stand movement for parkinson's disease patiants is proposed. The model expresses the motion of center of gravity by using a telescopic inverted pendulum model. In order to identify the relationship between the velocity at seat-off and floor reaction force, the experiment is carried out. Based on the experimental results, a floor reaction force was made. By obtaining the floor reaction force, the velocity at seat-off can be changed. We conclude that the model can express sit-to-stand movement in success and failure.

View full abstract

In Basketball, the number of non-contact ACL injuries which has been reported is greater than that of contact ACL injuries. According to report, Knee-in Toe-out posture is the most major causative factors for non-contact ACL injuries during basketball. However, there are other opinions such as the Knee-out Toe-in to be the injury posture, and the specific injury factor is not yet elucidated. The aim of this study is to elucidate the injury mechanism by simulating the strain of ACL. The position of ACL were determinate from 3D knee models which were created from computer tomography images. The knee models were created at 0°-120° flexion. Gradation maps of ACL strain during different posture were made to verify injury posture.

View full abstract

This paper describes motion analysis of a lower limb movement during a pedaling movement of a cyclist with the iliotibial band syndrome. The cyclist's lower limb movement is analyzed by a three dimensional motion analysis system. In this study, two sets of experiments are conducted, in which the subject pedals on a cycle against a load with or without a cleat wedge on the cycling shoes. The experimental results show that the magnitude of the movement of the patella of the affected side is significantly larger than that of the unaffected side. Furthermore, it is found that the cycling shoes with adequate cleat wedge decrease the magnitude of the movement of the patella in the coronal axis.

View full abstract

The objective of this study was to design an orthosis during the exercise of walking in water for the rehabilitation of ACL injury. In the rehabilitation of ACL injury, it is necessary to train the muscles around the knee joint. In particular, compared to the knee flexors, the knee extensors are less exerted in the normal walking form while walking in water. Therefore, the orthosis, by which the knee extensors can be trained, was optimally designed by the simulator which can compute the body load considering the fluid force and force acting on the ACL. The characteristics of the orthosis obtained by the simulation are the large width of the thigh and foot parts and the small density of the shank and foot parts. Second, the orthosis was manufactured based on the simulation design. Finally, the effectiveness of the manufactured orthosis was confirmed by comparing the muscle force analyzed in the simulation with the electromyogram measured in the subjective experiment.

View full abstract

This paper describes the development of the fall database for a biomechanical simulation. First, data of children's daily activities were collected at a sensor home, which is a mock daily living space. The sensor home comprises a video-surveillance system embedded into a daily-living environment and a wearable acceleration-gyro sensor. Then, falls were detected from sensor data using a fall detection algorithm developed by authors, and videos of detected falls were extracted from long-time recorded video. The extracted videos were used for fall motion analysis. A new CV algorithm was developed to automate fall motion analysis. Using the developed CV algorithm, fall motion data were accumulated into a database. The developed database allows a user to perform conditional searches of fall data by inputting search conditions, such as a child's attributes and fall situation. Finally, a biomechanical simulation of falls was conducted with initial conditions set using the database.

View full abstract

Excessive pronation in running is known to be one of the dominant causes of running injuries. In order to prevent it, the trilateral relationship of pronation, foot anatomy, and shoe structure has been studied in detail up to now. In addition, we assumed that the foot position at the heel contact (HC) and running speed could also affect pronation significantly. Then, we studied the relationship among foot motion, shoe sole stiffness and running speed using a multi-regression analysis. We conducted several experiments using 11 experienced runners, an optical motion capture system, a treadmill with two different speed and two types of running shoes with different inner-sole stiffness. Consequently, in low-stability shoe, pronation could be estimated primarily by foot position at HC and this relationship between them depended upon running speed. In high-stability shoe, on the other hand, the same relationship could not hold, probably due to other primary personal factors.

View full abstract

The purpose of this study was to examine kinematics and kinetics of the ankle joint in transverse plane at several walking speed and several turning angle. Six healthy male subjects walked and turned 45,90 degree at several walking speed. Landmark positions and ground reaction force were recorded by 10 high-speed cameras and 3 force-platforms, simultaneously. Kinematics data (angle and angular velocity) and Kinetics data (torque and power) were calculated. The result showed that internally rotation angle and externally rotation moment of normal and slow walking speed were significantly lower than those of fast walking speed during turning 45 and 90 degree. And the result showed that Int / Ext rotation moment of turning 45 and 90 degree were significantly higher than those of straight walking. And passive torsional springs were chosen to model the ankle behavior in gait cycle. The result of this study showed that elements of walking speed and turning gait are very important when ankle behavior in transverse plane is examined and modeled.

View full abstract

In general, foot joint torque is calculated from the ground reaction force obtained from a force plate. However, in order to predict the torque precisely, it has been needed to consider the ground reaction force distribution in the contact area between foot and ground surface, hi this study, we establish a new technique to calculate the metatarsalphalangeal (MP), tarsalmetatarsal (TM) and ankle joint torques from the 3 dimensional ground reaction force distribution obtained from the sensor shoes, which has 6 miniature force sensors in 19 positions. The result explained that the joint torque calculated by the proposed technique could predict more accurate than that calculated by the conventional method, hi comparison of the joint torque components at 19 local positions in the contact area, contributions of the torque components to the joint torque was clarified during stance phase. Furthermore, influence of sole thickness on the joint torques was quantitatively discussed.

View full abstract

Taking two crutches, which have different shapes of the tip, we investigated the effect of the shape of crutch on energy consumption during crutch gait. We carried out experiments using motion capture system. We calculated an energy consumption and upper limb load by 2D model using experimentally measured data. From the result, we found a greate difference in energy consumption. Energy consumption decreased by 56.4% by using a crutch with a special shape. This reason was investigated with respect to the movement of the contact point of crutch and floor and force applied at the contact point.

View full abstract

The purpose of this study was to quantify the stability of ankle joint and promotion of muscle activity in walking with some kind of insoles which have different shock-absorbing capacities. To accomplish this, three-dimensional coordinate data, ground reaction force(GRF), and electromyogram data during stance phase were measured simultaneously. Eight healthy male subjects walked the ten meter laboratory walkway at his self-selected comfortable walking speed . Empirical results suggested that : (1) stability derived from maximum foot eversion angle value was not significantly different between consisting low-resilient material or not; (2) muscle(Gastrocnemius Lateral head) activity in second double limb support period was significantly different among conditions. From these results, that insoles with low-resilient material encourage muscle activity in propulsion phase with keeping stability.

View full abstract

The purpose of this study was to quantify the functional role of compressive characteristics of shoes sole by combining a fmite-truss-element shoes model and equation of whole-body motion. The equation of the shoes sole deformation was developed by modeling shoes sole as a construction of truss elements with nonlinear spring and damper properties. The coefficients of the properties were identified from impact test by using an impact device consisting of accelerometer and arm with impactor. The equation of whole-body motion was derived by modeling the human body as a system of 15-rigid linked segments. Dynamic contributions of the support leg joint torques, which were caused by the elastic and viscous property of the shoes sole, to the generation of whole-body CG's acceleration were calculated under constant running speed condition. The results in this study indicate that 1) the plantar flexion torque about the ankle caused by the elastic property of the forepart of shoes sole contributes to the acceleration of whole-body CG, and 2) the flexion torque of the knee caused by the viscous property of shoe sole contributes to the absorption of the vertical impact force occurred at foot contact.

View full abstract

This paper describes shock attenuation effects for court category shoes. The shock attenuation mechanism has been clarified for running shoes. The attenuation of lower frequency vibration on tibia is effective for the designing comfortable running shoes. On the other hand, it has been known that vibration with the higher frequency range rather than running is excited in court category such as tennis, volley and handball. This is mainly derived from the difference in motions. First, landing after spike jump in volleyball is focused and the ground reaction force, acceleration on tibia, local foot pressures and sole thickness were measured in synchronization. The landing onset is at toe and the contact area spreads to midfoot and heel. The higher frequency vibration is mainly excited at heel contact and the input to player is equivalent with a half sine wave. Secondly, high frequency vibration effects on human are investigated by using the vibration testing system. Therefore it is concluded that human feels a discomfort at the vicinity of 60Hz, which is derived from a chest resonance. At the same time, the heart rate also rapidly increases. These phenomena make a bad influence on players' performance. An attenuation of the higher frequency vibration is one of the important functions in the designing process of the court category shoes.

View full abstract

The purpose of this study is to investigate an applicability of multi-intensity impact test and viscoelastic modeling proposed in previous studies to a long pile synthetic turf and considering the shock attenuation of the long pile synthetic turf by using simulation method. The multi-intensity impact tests and the parameter identification method of the exponential function type nonlinear Voigt model were performed to two kinds of long pile synthetic turfs with different hardness. The hardness of these two specimens were controlled by changing the ratio of filling materials, i.e. sand and rubber chip. After a parameter identification of the model, shock attenuation properties were considered with two kinds of synthetic turf and one of the popular polyurethane synthetic surface certified by IAAF. Although the identification accuracy of some trials were not so high, it is possible to apply the parameter identification method and the estimation of shock attenuation by using the simulation to the long pile synthetic turf. Because the low accuracy should be improved by modifying the testing conditions such as the impact area, the stability of test foot and the uniformity of surface condition of the synthetic turf.

View full abstract

For several decades, factory automation or unmanned factory productivity has been progressed to realize much higher productivity in manufacturing. However, human centered manufacturing system is getting attention to realize much more flexibility for manufacturing of wide product variety and volume. In this study, a mechanism of muscle fatigue is investigated, and a muscular fatigue model to evaluate muscle fatigue progress under several muscular force patterns is proposed. Furthermore, the endurance time for keeping constant force by the participant is estimated considering physical characteristics of the participant. In order to show the effectiveness of the proposed method, experimental verifications were conducted. The experimental results had a good agreement with the evaluation of muscle fatigue progress using the proposed method. The proposed model contributes to evaluate the ergonomic working environments and the comfortable working motions.

View full abstract

In this paper, human muscle tension estimation based on robotics dynamics and its visualization technique was reported. Human muscle tension estimation was obtained by kinematics and dynamics using optical motion caputure data, force plate data and EMG signals. The environment for the motion capture and the calculation flow was explained. The visualization technique was explained. Tai chi, tap dance and drum motion was analyzed, respectively. The obtained findings of the experts' motion technique were reported.

View full abstract

Estimation of muscle forces during human motions is important in the fields of sport, ergonomics and bioengineering in order to improve sport techniques, rehabilitation procedures, product designs and work environments, and so on. In general, in the musculoskeletal models that have been developed, the functions of antagonistic muscles and biarticular muscles are not considered to estimate muscle forces. In this study, a musculoskeletal model that considered the functions of the antagonistic muscles and biarticular muscles was investigated. In this model, muscles acting across the hip, knee and ankle joints were treated simultaneously. Furthermore, in this study, standing long jump as dynamic motion was conducted to validate the proposed model to estimate muscle forces. Surface electromyograms (EMGs) of tibialis anterior, gastrocnemius, soleus, rectus femoris, vastus lateralis, semimembranosus, biceps femoris and short head and gluteus maximus were measured to compare with the estimated muscle forces. The experimental results showed that the muscle forces estimated by the proposed method had a good agreement with the EMGs of muscles.

View full abstract

Surface Electromyogram is used in many situations in order to improve the performance of physical activity. In addition, we can know the status of the muscle with comparative ease by using it. So we optimized the activity of the muscle in relation to softball pitching motion using musculoskeletal model of the upper limb. We propose a training system that able to physical exercise with compare obtained waveforms of muscle activity by optimization using Multiobjective Genetic Algorithm and during measuring own surface Electromyogram.

View full abstract

The purpose of this study is to determine the muscle function considering the contraction mode during the support phase in running. Four male runners ran at 4m/s and marker's trajectories and ground reaction forces were measured by a motion capture system and a force plate, respectively. The musculoskeletal model was developed by the SIMM software, and muscle forces of the support leg were estimated from the joint torques of the leg calculated by the inverse dynamics approach. The contribution of the support leg muscles to the propulsion/braking and support (i.e. forward/backward and upward acceleration) of the body CG (center of gravity) was derived from a dynamics analysis based on the equation of whole-body motion. The results show that (1) the quadriceps muscle group contributes to braking and support by muscle forces of both eccentric and concentric contraction in braking phase, and contributes to those by the only concentric contraction in propulsion phase, (2) the soleus was the greatest contributor to propulsion and support during support phase, and (3) the muscle energy, in especially eccentric contraction phase, was effectively converted to CG acceleration as compared with other muscles.

View full abstract

The effective use of rice-husk presently stands as a priority issue. Rice-husk contains cellulose and silica each 75wt% and 25wt%. This silica is called 'Plant-opal' and has a unique shape. It expected to scratch effect by plant-opal. In this study, the plant-opal that is of high purity seceded from rice-husk and the rubber including the plant-opal was measured about dry and wet grip performance. Cellulose was decomposed by cellulase for plant-opal separation. The sample adding plant-opal had a higher coefficient of friction than no filler sample. Plant-opal content reached an optimum level at 5phr. Coefficient of friction was gone up by the silica component of plant-opal and the unique shape.

View full abstract

Ski boots are important for assisting progress in ski turning technique as an interface between a skier and a ski. In the alpine races, suitability of ski boots is important for quick and accurate lean motion of a skier in ski turns. This study is aimed at building the new design of ski boots that can improve the results of alpine ski races. In this paper, the new design of lower shells of ski boots that can keep center position and adjust the application point of reaction vector on the bottom of ski boots, was examined. Finally, the effectiveness of the new design of lower shells has been verified in field tests by Japanese alpine ski racers.

View full abstract

Generally, it has been said that hill walking (HWK) may cause lower-extremity injury and slip accident. One of the reasons is that muscle fatigue in HWK is much higher than that in flat walking. However, there are little studies that have discussed relationship between sole designing and kinetics in HWK, especially in camber walking. The purpose of this study is to clarify footwear requirement properties concerning muscle fatigue reduction in HWK. To consider characteristic parameters of kinetics in HWK, motion analyses on 5 surface conditions (flat, 2-cambers: medial-tilt and lateral-tilt, downhill (Dw), uphill) were carried out. It was confirmed that large ankle power and large knee power in DwWK were found in the early stance phase. We discussed the relationship between these parameters obtained from shoes with various rear-foot structures in DwWK. In the result, the shoe whose rear-foot hardness was low and rear-foot bevel angle was close to the slope of hill surface could reduce muscle fatigue in HWK.

View full abstract

Traction between footwear and surface is crucial to improving performance and preventing lower limb injuries. In field sports such as soccer, the cleats penetrate and interlock with the playing surface. The purpose of this study is to obtain elementary information for sole designing in soccer boots. Soccer boot traction depends on cleat geometry and arrangement. The proposed technique with miniature sensors measures ground reaction force (GRF) distribution. By using test boots with 16 cleats and miniature sensors, the force components loaded on each cleat are measured in the side step motion. Length of step are 70, 90, 110cm. GRF distributions are also measured using boots with different cleat arrangements. The effects of cleat arrangement on GRF distributions are quantitatively evaluated.

View full abstract

The purpose of this study is to construct the viscoelastic model of human body for evaluation of sprint spike shoes from the view point of sprint performance. Subjects wore some spike shoes and performed vertical continuous hopping by only ankle. Then as the model of simulating landing shock wave, we constructed viscoelastic model by three element from mass, spring and damper. Furthermore, we assume that increase of jumping frequency is continuity and constructed continuity viscoelastic parameters. As the results, viscoelastic parameters fit variation of actual movement in crural. And these parameters change by wearing spike shoes, there is a possibility that these model parameters are evaluation indexes of spike shoes.

View full abstract

In synchronized swimming, a swimmer exerts forces on the other swimmers in the water. There have been no methods to analyze such mechanical phenomena to date. Such analytical method is promising to acquire new findings which will be useful for the improvement of performance The objectives of this study were to develop the simulation model for the analysis of synchronized swimming by applying the swimming human simulation model SWUM to it, and to conduct the simulation analysis. In the present study, "lift". (One of the techniques of synchronized swimming) was taken as the target of the simulation. The simulation model for the lift was constructed and a simulation analysis was conducted by inputting the information obtained in the experiment. The simulation result was consistent with the experimental one, indicating the sufficient validity of the simulation.

View full abstract

During shooting motion in water polo, the shooter is subjected to the fluid force. Therefore, through the use of the fluid force generated by moving upper limb and lower limb, it is important to keep own balance and deliver enough power to the ball. However, there have been no method of analysis for dynamics of shooting motion considering the fluid force. The objectives of this study were to develop the simulation model of shooting motion in water polo, and to conduct the simulation analysis using the developed model. For the objectives, we constructed the simulation model and conducted experiment to obtain the data of shooting motion. We conducted a simulation by inputting experimental data into the simulation model and validated the model. As the result, this model was found to be effective.

View full abstract

The purpose of this study was to examine if the escalation of leg-sinking effect of buoyancy around the center of mass (CM) during breathing changes due to different breathing patterns -- chest breathing and abdominal breathing. Five male participated in this study. The positions of the CM, the position of the center of volume (CV), and distance between CM and CV were determined. The results showed that CV-CM distance increased for 1.47cm with chest breathing and for 0.94cm with abdominal breathing. As a result of these change of distance, the leg-sinking effect increase for 10.27Nm with chest breathing and for 6.40Nm with abdominal breathing. The small leg-sinking effect decrease the energy cost of swimming. The results of this study indicates that abdominal breathing reduces the leg-sinking effect of buoyancy, suggesting that abdominal breathing may improve the performance of swimming.

View full abstract

Freestyle swimming is technically challenging and also can be difficult to analyse. Understanding the various actions, such as armstroke, kick, and body roll, is important for performance analysis. Inertial sensors can biomechanically capture temporal kinematics. Measuring the timing and coordination of the kinematics associated with armstroke, kick, and body roll provides performance analysers with a means to quantify progression of a swimmer's development. Video use is the typical method for analysis, however, there are shortcomings with this system. Inertial technology can overcome some issues. Outcomes from this study indicate that patterns in the inertial sensor data are consistent. Therefore assessment is possible. Not only for each individual variable of armstroke, kick, and body roll, but also relative to each other.

View full abstract

Assessment of swimming biomechanics is challenging because the activity is water based and is not stationary, nor can easily be simulated as such. This paper introduces sensors fusion tools to combine several technologies to enable a more robust investigation into the movements of swimmers. Swimming assessment is traditionally a labour intensive process where even the primary measures of stroke phase, stroke rates, stroke counts, and lap times have to be manually recorded or extracted from video data. While more detailed stroke information can be gathered from inertial sensor and video data it is time consuming and manually based. Recent advances in microsensors have demonstrated the validity of using wearable sensors to replace these manual methods in an automated way [1] and the potential to further extend the capability to detailed biomechanics measures [2] though the use of multiple sensors per swimmer. The use of microsensors however introduces new complexity through the collection of large amounts of data that need to be collected, saved, synchronized, and appropriately conditioned prior to analysis. Analysis techniques include filtering, event detection and display in a form useful for a range of audiences including athletes, coaches, sports scientists and researchers. This paper describes tools developed that facilitate the use of microsensor technology and its fusion with other data sources.

View full abstract

In this study, the optimal arm strokes in crawl swimming which maximize the swimming speed and propulsive efficiency were solved computationally. For this objective, an optimizing method which consisted of the random search and the PSO (Particle Swarm Optimization) algorithm was constructed. In order to consider the muscle strength characteristics of the swimmer as the constraint condition of the optimization, an experiment to measure the maximum joint torques was carried out for various joint angles and angular speeds. Using the measured experimental data as the reference values, a musculoskeletal simulation model was constructed. By the constructed musculoskeletal model, muscle strength characteristics in various conditions were investigated and used to create a database. Using this database, the optimizing calculation was finally conducted and the following results were obtained: In the optimization maximizing the swimming speed, the swimming speed became maximum when the stroke cycle was 0.9 s. A relatively I-shaped stroke was obtained in this case. In the optimization maximizing the propulsive efficiency, the propulsive efficiency became maximum when the stroke cycle was 1.3 s. A relatively S-shaped stroke was obtained in this case. Two strokes which respectively maximized the swimming speed and propulsive efficiency were very similar to each other when the stroke cycles were the same. The swimming speeds and stroke cycles obtained in the optimizing calculation were within reasonable ranges compared to the actual races.

View full abstract

This paper deals with route, or path, planning for a very long distance swimming in the sea by applying project management method and optimal guidance scheme. The objective of the long distance swimming is to maximize the number of successful swimmers while reducing the risk that may be encountered during the trial. We use an example of long distance swimming carried out by swimming club of Keio University. First we have picked up the factors for increasing the successful swimming rate with emphasis on the safety. Then, we apply a modified dynamic programming approach to get a feasible solution for the complex problem affected by many dependent factors. After considering how to reduce the risk while finding a decision or method to solute the problems, we have obtained a solution to this long distance swimming across the sea. Furthermore, this result turns out to be useful to improve the successful rate and to identify important factors arising from natural phenomenon, such as tidal stream which affects the successful rate.

View full abstract

The purpose of this study was to find out the effects of men's swimsuits on swimming position and muscle activity in gliding motion. For this objective, the swimming experiments to measure electromyogram and gliding position in sagittal plane simultaneously were conducted by using 3-types of men's swimsuit (A,B, and C). Next, we compared experimental results one-on-one between swimsuits by ANOVA (analysis of variance). The results of experiment and ANOVA showed that in wearing Swimsuit C, compared to Swimsuits A and B, hip became lower to shoulder (p<0.05), hip joint became more extended (p<0.05), and muscle activity of ES (Erector Spinae) and drag coefficient had tendency to decrease. In addition, we established a new index which is corrected muscle activity of ES considering the difference of hip joint angle. We confirmed statistically that Swimsuit C had effects of extending hip joint and/or reducing muscle activity of ES (p<0.05). The reason for this was considered to be that the high tension to direction of extension of hip joint produced these Swimsuit C's effects by helping the muscle to extend the hip joint.

View full abstract

In this paper, establishment of design methods for competitive swimwear using numerical analysis was investigated. Now, FINA's regulations permit to make competition swimwear by the fabric material. The fabric materials have two mechanical properties. The one is nonlinear elasticity which is regarded as hyperelasticity like rubber. Another is anisotropic that depend on the directions of two fiber families. Therefore, an anisotoropic hyperelastic model was proposed for the mechanical behavior of swimwear materials and the applicability of the FEM method to the swimwear materials was shown. The properties of swimwear fabrics were estimated by uniaxial tensile tests. From the test results, the material parameters for anisotropic hyperelasticity were determined by the nonlinear least square methods. The simulated results calculated by FEM were also shown to investigate the applicability of numerical simulation to the design of competition swimwear.

View full abstract

In this study, deformation of the skin around a knee in a flexion action is measured by the noncontact three-dimensional deformation analysis system based on image processing method. The system enables to measure the deformation of the skin under a clothing pressure if the see-through clothes are worn. The conditions with or without pantyhose are considered, the non-worn skin, pantyhose surface and skin under the pantyhose are selected as the measurement objects. The skin is stretched with the large strain over 60% at the 30-40mm upper point from the top of the patella. The bi-axial tension is observed around the top of the patella, the compression with about 40% strain in popliteal region. The pantyhose are deformed with the same tendency as the non-worn skin, but the deformation is small. The deformation of the skin under the pantyhose is also small except for the case with low clothing pressure. Because of this, it is considered that the pressure inhibits the deformation of the skin under the pantyhose.

View full abstract

The objective of this study was to propose the above-knee prosthesis for swimming which focuses on ankle joint motion. For this objective, we conducted experimental tests to examine the effects of ankle joint motion for prosthesis on swimming performance. In the experiment, one subject swimmer put on a standard endoskeletal prosthesis and the prosthesis which enabled four ankle joint conditions. The flutter kick and crawl swimming were performed. Questionnaire evaluations were also conducted. From the experimental results, 'supported by spring' prosthesis was acquired the best evaluation since the fluid force acting on the foot part of the prosthesis became equal to that on the normal foot. We showed the possibility that the swimming performance closer to that of healthy people with better balance can be achieved by the appropriate support of the ankle joint motion.

View full abstract

The purpose of this study was to describe three-dimensional scapular translation and rotation during arm elevation. Thirteen male subjects performed humeral elevation in the scapular plane. The location of the center of mass (CoM) of the scapula was determined using the existing skeletal model of the scapula. Based on the helical axis, the scapular rotation axis were computed. During humeral elevation, a) the position of the CoM of the scapula relative to the thorax moved superiorly and medially, b) the lateral (upward) rotation and posterior tilt angles of the scapular attitude were changed at a constant rate, c) the orientation of the scapular rotation axis was nearly constant, d) the location of the scapular rotation center on the scapula moved medially from the acromion. These results indicate the mechanical relationship in which the time-history of the rotation axis orientation and position determine the attitude and position of the CoM at any given instant during the scapular motion of interest.

View full abstract

Estimation of person's joint moment is very important in the field of the medical treatment and sports. In order to calculate a person's joint moment using inverse dynamics, data of mass and position of the center of gravity of each part of the human body are necessary. However, in the present state of affairs, general statistical data are used and it causes low precision of the estimation because the subject's own data are not used. In this study, we develop a new method to identify the mass and position of the center of gravity of each part of the subject. Multiple regression analysis is carried out using 3-dimentional coordinates of the parts of the subjects and the ground reaction force. To evaluate the accuracy of the proposed method we carry out numerical simulation and demonstrate the calculation results.

View full abstract

In the use of a laser pointer, tremor counteracts human's control and leads to less accuracy. The objective of this study is to develop a laser pointer with active suppression of the effect of user's tremor. We measured human tremor in the use of a laser pointer and analyzed it in time and frequency domains. As the result, difference in acceleration between in stationary and moving situations was clarified. This result leads to recognition of user's intention if he/she desires to keep or move the pointing position or not. Additionally, we proposed a control strategy to suppress user's tremor effect which combines feedforward based on BMFLC and feedback controllers. Result of the simulation applied this strategy showed its effectiveness.

View full abstract

In the sprint, the sprinters are required to use starting blocks at the crouch start. Therefore, it is important to clarify the technique of block clearance in order to improve sprint performance. The purpose of this study is to examine the technique of block clearance from joint torque and joint power in lower extremity applied to the starting blocks by sprinters. From starting blocks, six sprinters did the "starting dash" as is done in a sprint running race, and the forces applied to the right and left starting block were measured by with the force plates (1kHz). And, the block clearance movement was recorded by Hi-speed camera (250Hz). The results can be summarized as follows. There were two different patterns about the joint torque and power applied to the rear block. The type of pushing the rear block was presumed to have exhibited the extension torque and power at the hip and ankle of the rear leg. On the other hand, the type of pulling the rear leg from the rear block was presumed to have exhibited the flexion torque at the hip and the extension torque and power at the knee and ankle of the rear leg.

View full abstract

The purpose of this study was to clarify characteristics of movement of sprint running on curve in elementary school children. 30 fifth or sixth grade children in elementary school participated in this study and they performed 50m sprint on curve (R=12.5m) and straight tracks. Children were divided into high-level group (n=10) and low-level group (n=10) based on 50m sprint time on straight track in this study. Children's sprint form on each track was filmed by two video cameras and high and low-level group children (n=20) was analyzed by the three-dimensional direct linear transformation (DLT) method. Results were as follows: 1) Elementary school children did proper inclination movement of their body according to their sprint ability and centrifugal force which affected the center of gravity when they sprinted on curve tracks. 2) In high-level group sprint on curve track, it is considered that left leg has a role which obtains propulsion and right leg has a role which resists the centrifugal force of the center of gravity. 3) It is considered that use of left leg which has a role of obtaining propulsion is concerned with cornering skill, and children who had superior cornering skill sprinted on curve track with a range of direction change during left foot contact and flight phase small.

View full abstract

The objective of this study was to construct a finite element (FE) model which can accurately simulate the rebound behaviour of a ball including a spin axis for a golf impact, and to investigate the effect of a position of centre of gravity (CoG) of a clubhead on the ball rebound, by conducting an FE analysis on a ball colliding with a simplified club. The club was constructed by holding the simplified clubhead in a locking ring fitted onto a steel shaft. The club model with linear elasticity was constructed. A ball model with hyperelasticity and viscoelasticity was constructed using solid elements. Impact experiments were also conducted to devise a method for calculating a spin rate and axis using a rotation matrix and to also confirm the accuracy of the FE model. The simulated results closely matched the experimental results. The ball rebound was analysed using the constructed model by varying positions of the height and depth of the CoG. The rebound angle and backspin tended to be depended on the height of the CoG and the variation seemed to be influenced by the tangential force of the impact face. In the toe and heel impact cases, the deviation angle and sidespin tended to increase with the depth of the CoG and a component of impact force, which led to a generation of the sidespin, was identified from the relationship between the variation of the sidespin and positions of the depth of the CoG.

View full abstract

In order to investigate the effects of ball structure on spin rate of golf ball, impact phenomena between a golf club head and a golf ball was simulated by the finite element method. As results, the following two points are obtained. Firstly, spin rate gets maximum value at a certain coefficient of friction in any loft angle of club head and is affected by ball structure through the larger coefficient of friction then the certain coefficient of friction. Secondly, spin rate depends on the distribution shape of Young's modulus on radial direction, and a larger ratio of outside to inside rigidity of ball causes a smaller spin rate. That is, it is considered that the distribution shape of rigidity is dominant to the reverse time of tangential force.

View full abstract

This sheet deals with analysis of the oblique impact system, which is composed of the golf-ball and club. 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 ball. The characteristics of the oblique impact were obtained by using this model. In previous studies,the validity of the normal model was confirmed, validity of tangential model was not confiemed. Therefore, reconsider the tangential model. The result is improved accuracy of the model. Also.examined the characteristics of oblique impacts of changes in coefficient of friction from experiments and analysis.

View full abstract

This paper discussed the proposal of tennis ball recycling required by environmental problem and introduced research and development of high quality recycled ball named "ECO Ball". Furthermore, it showed the effect of felt called Melton on the spin behavior and the ball control by comparison between a tennis ball and a smooth surface ball without felt. It also discussed the characteristics of used balls with variety of felt composed of wool and nylon and its relation to the variety of court surfaces.

View full abstract

Distance and accuracy are required in golf swing. In order to hit a shot of maximum distance, swing linear velocity at impact phase must be maximum. Since dynamics of club and arm dominates the overall behavior of the swing, the dynamical mechanism of the arm and the club must be clarified for understanding the mechanism to produce the maximum velocity of the club. As a step toward understanding the mechanism, we investigated how non-muscular (e.g. centrifugal, Coriolis, and gravity) forces of the each link generates, absorbs, and transfers mechanical energy in order to produce the maximum velocity. This was accomplished using multi-body power analysis derived entirely from dynamical equations of a three-dimensional double pendulum with moving pivot model.

View full abstract

In order to kick a ball of maximum velocity, swing linear velocity at impact phase must be maximum. The aim of this study was to clarify mechanism of produce maximum velocity of the foot using mathematical analysis based on a three-dimensional double pendulum with moving pivot model. We investigated how non-muscular forces of each link generates, absorbs and transfers the energy in order to produce the maximum swing velocity of the leg.

View full abstract