It is widely accepted that stability of bodily movement is a key to studying skills. We can however not explain what the stability is. We took as an example of skills the walking on stilts and investigated how the bodily movement of the experienced are different from those of the inexperienced. We analyzed the difference in terms of stability of periodic movements. As a result, it showed significant differences between the experienced and the inexperienced.

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We studied a skill acquisition process of samba dancing. We investigated the acquisition process by employing 30 subjects for six months. We installed a wireless accelerometer at the back of lumbar to measure acceleration of their movements. We analyzed collected data by evaluating autocorrelation and frequency analyses. We found that many subjects learned to keep a correct tempo of music during six months. We also found that several subjects showed accent of rhythm, which is necessary for samba. We expect that there are two stages of skill acquisition process of samba dancing: tempo and accent. We also measured acceleration of the arm movement of playing the shaker while subject is dancing. We found that several subjects showed accent of rhythm on playing the shaker as well as case of dancing. We expect that showing accent by dancing is necessary to show accent by playing the shaker.

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One of the main difficulties of motor skill acquisition is descended from body control based on wrong mental models for the related target domains such as sports and music instrument playing. In order to acquire adequate motor skill by modifying such false belief, we need to support one to find appropriate key points to achieve the given task. In this paper, we investigate two approaches to realize such support: clarifying one's motor skill through meta cognition and representing motor skills by appropriate mechanical models. Furthermore we study a possibility to build an integrated model which takes relationship of plural key points into account. We also investigate methods of rules integration to achieve compound tasks. These ideas suggest the possibility to create new skill rules to perform difficult tasks automatically.

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Unlike common footwear, high heels have a role which makes standing position look as beautiful as possible for ladies. Compared with common walking shoes, it has been said that high heels has disadvantages in the performances. Here, the performances indicate sole stability, cushioning, smooth guidance and so on. The establishment of the high heel designing system pleases many ladies for performance as well as standing position. In this study walking motion analyses with high heels and some walking shoes with different sole structures are carried out. Judging from these analytical results, some quantitative parameters related difficulty in walking with high heels is identified. In order to improve the parameters, the relationship influences of heel plug shape and position on walking motion are quantitatively investigated. Therefore, it was confirmed that the heel plug shape and geometry were important designing parameters.

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A wearable sensor system for gait analysis is presented, which is composed of a combination of motion sensor modules and a 6-aixs reaction force sensor. Experimental study was implemented to estimate orientations of leg segments and measure foot reaction forces during walking. Based on the quantitative motion and force analysis, this system can detect the following gait phases from clinical study: initial contact, loading response, mid stance, terminal stance, pre swing, initial swing, mid swing and terminal swing.

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The purpose of this study is to optimize the stiffness distribution of shoe sole under various moving speeds. The optimization is quantitatively evaluated by the propulsion impulse under each moving speeds. In other words, smaller propulsion impulse is equivalent with better shoes. The propulsion impulse is calculated by the forward ground reaction force. Forefoot bending stiffness makes a great influence on the propulsion impulse. Eigenfrequency analysis is applied to the sole stiffness evaluation. By using both the eigenfrequency analysis and ground reaction force measurements, the relationship between sole stiffness and the propulsion impulse under 3 moving velocity, 1.63m/sec, 1.91m/sec and 4.87m/sec are investigated. Therefore it was confirmed that the optimized sole stiffness distributions were affected by the moving speed.

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Nowadays trail running which is a running on rough roads in forest and mountain is in fashion. Footwears' requirement properties depend on applications. For instance requirement properties of running shoes are cushioning, stability, forefoot flexibility, fitting and so on. However the direct application of the running shoes designing method to the trail running shoes is not valid. The purpose of this paper is the proposition of the trail running shoes evaluation method. Motion analyses under various sloped down hill running (SDHR) are performed and compared with acceleration histories obtained from shank. It is confirmed that footwear stability on SDHR could be evaluated by the acceleration history. By using the acceleration history, stabilities of 5 typed shoes with various midfoot torsional stiffness are evaluated and the relationship between sole stiffness and stability on SDHR are discussed.

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A purpose of this study is to measure bone strain induced electrically-controlled muscle contraction and compare with that recorded during walking exercise using an animal model. A strain gage technique was used to measure strain on a rat femur when a rectus femoris muscle is stimulated electrically in a sinusoidal waveform at a peak voltage of 0, 1, 3, or 6V, and during walking exercise(4m/min) by a treadmill. Bone strain recorded in 6V-muscle stimulation was 65% larger than that in treadmill exercise. This result suggests that electrically-controlled muscle contraction could be useful as a new mechanical stimulation method to elicit osteogenesis response.

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The purpose of this study was to examine the validity of estimated muscular tension using the musculoskeletal model during forward lunge and squat. Eighteen healthy men were enrolled in this study. A correlation coefficient was calculated between the estimated value for the muscular tension and the root mean square (RMS) value for the electromyographic recordings. Electromyographic data was obtained from vasti medialis (VM) and lateralis (VL) and rectus femoris (RF). The mean values of coefficient correlation for VM and VL exceeded 0.61 during the flexion and extension phase of forward lunge. The coefficient correlation for squat fell below 0.44 for during the flexion and extension phase, and RF, it fell below 0.30 during forward lunge and squat. Similarities of the waveform patterns exceeded 0.93 between estimated muscular tension and electromyographic RMS for both forward lunge and squat. The value of the estimated muscular tension for RF for both exercises was found to be very small. In conclusion, the output pattern for the estimated muscular tension was validated, although further study is required to examine the value of muscular tension, in particularly, of a two-joint muscle such as RF.

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Osteoporosis causes frequently bone compressive fracture of the vertebrae as coexisting illness. To strengthen osteoporosis vertebra, drug therapy are often treated in clinic. It is important to evaluate mechanical strength and betterment of bone fracture risk of vertebra in this treatment process. To estimate them noninvasively in detail, patient-specific mechanical analysis is necessary because mechanical strength of vertebra depends on patient-specific factors, which are shape, cortical thickness, density distribution of cancellous, and so on. In our previous study, finite-element (FE) models derived from CT images provide good prediction of vertebral strength, and effect of treatment was demonstrated clearly. In this study, FE to predict bone fracture force for 4 osteoporosis vertebrae was also performed following drug treatment process over time. Availability of evaluation method of vertebral strength using bone fracture analysis was discussed.

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Spine structure is mainly constructed of many vertebrae and flexible intervertebral disks, and it is unstable by itself under standing condition. Supporting by erector muscles and ligaments keep the spine standing condition, so that boundary condition of each vertebra depend on the muscle and ligament forces. Moment applied to vertebra by intervertebral disk deformation also has to be considered for the boundary condition of vertebra. Biomechanical simulation of musculoskeletal model taking account of muscle and ligament forces and intervertebral joint moments is necessary to determine the boundary condition of vertebral analysis. In this study, a thoracolumber musculoskeletal model around lumber vertebrae and hip joint was developed, and loading condition of each vertebra was analyzed considering muscle and ligament forces and joint moments. Muscle forces and intervertebral joint moments were evaluated varying flexion or extension angle, and efficiency of the musculoskeletal model and proposed method to obtain the muscle forces and intervertebral joint moments was discussed.

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Human locomotion system has 'pull-in effect', in which if the ground swings with specific frequencies in one's frontal plane, a human's gait rhythm changes into the ground swinging frequency from one's natural gait rhythm. However the cause of the effect is still not clear. This paper notices human's posture controlling system, and refers to the cause of pull-in effect with suggesting a dynamical human gait model which has two legs and posture controller. Firstly the features of pull-in effect are clarified experimentally and secondly the posture controller which works for stabilizing frontal body behavior is studied. Then a dynamical human gait model is established from the results. The model consists of two beams and a mass representing legs and center of gravity of one's body. It basically behaves passively, but only the posture is controlled actively. The model shows the features of pull-in effect very well, and looking at the behavior of the model, it is explained that the posture controller causes pull-in effect.

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Wearing child restraint system (CRS) for children under 6 is obligated by law since 2000 in Japan. A CRS has great influence in crash-safety of children. Therefore, much further improvement of the safety of CRS is requested. In this study, the effects of CRS shapes and material properties for crash-safety of children were clarified using crash simulations with child models and a CRS model. In addition, a CRS optimization to minimize injury risks of head and neck in both frontal and side crashes was carried out. As the result, we proposed a safer CRS for children. Dummy models (Hybrid III 3-year-old dummy model and Q3 dummy model), and a 3-year-old finite element child human model, developed by scaling an adult FE human model, were used in the study.

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The purpose of this study is to construct a method for visualizing dangers lurking in environments where children play. For this purpose, a risk map was created by using the simulation. For the simulation, a child multi-body model was created by using the anthropometry data, and existing body segment parameters for children were used. A parameter study was performed, and the influence of the inertial properties and the anthropometric dimensions on the behavior of falling was examined. Finally, taking the fall from a circular staircase attached to a playground slide as an example, falling accidents were simulated using the created model, and a risk map was constructed. As a result, unpredictable dangers lurking in the play environment could be visualized.

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This paper propose a new index for the characteristics of muscular outputs with cross section and volumes calculated by the three plane patterns (angular velocity-torque plane, angle-torque plane, and angle-angular velocity plane) on the three-dimensional surface. A peak torque was generally used to evaluate muscular strength and the evaluation with two-dimensional curve, such as force-velocity curve and force-power curve were utilized to evaluate the characteristics of muscular outputs as usual. However, even though muscular outputs among the subjects show similar experimental results on force-velocity curve, there are some cases where they show different characteristics on three-dimensional surface including angular data. In order to evaluate muscular characteristics, three-dimensional index including angle, velocity and torque value shows the detail property of muscular characteristics. We measured the elbow flexion for 9 subjects (different types of athletic events) with the system which generate isoviscous load. From obtained data we consisted of three-dimensional surface with angular position, angular velocity and torque data and calculated the volumes by three plane patterns. By using these indexes, we compared with the muscular outputs among different types of athletic events. As a result, these indexes showed significant differences among the athletic events.

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It is necessary for strength training machines, especially high speed and high power machines, to have safety mechanisms. In this paper we showed our developed strength machine with ER clutch. This machine could move with high speed, high power, high accuracy and safety. Even if this machine is out of control, operated lever arm rotates only up to 0.52 [rad/s] by using speed control of the input torque motor to ER clutch. And we verified the performance of our machine with the experiment of isokinetic load (0.52, 4.19, 8.72 [rad/s]). As the results of the experiment, this machine could display loads within every desired angular velocity ±5%. And this machine performed 44.4 [Nm] at maximum during 0.52 [rad/s] movement.

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In this research, positioning of the gaze point was systematically varied to predict the movement of the target. Here, directional images of the target moving to the right and left and faint images of the target were recorded by a digital camera. In addition, the feature to the time direction was added by the harmony calculation between frames of those images. The directional and faint images were then matched to predict the direction of movement of the target. The optimum position of the gaze point was then evaluated based on the difference of the matching degree for the outcome of the opposite directions.

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There is no robot around us in our society at the current stage and also there will be no robot in the future if we define a robot as an autonomous machine working in the arena of offices, homes, and disaster sites, etc. outside the factories and continue the present conventional research and development (R & D) style in robot projects. It seems that the emergence of intellectuality in an autonomous robot exists in the dexterity of human or creatures as complex systems. This paper proposed the approach for realization of a real intelligent robot. We call this Human-Robotics, where robots and engineers should learn and develop in collaboration with each other in the real world on the basis of the dexterity of nature, life and human. We showed in this paper as the case studies the humanlike robust NANBA walking & running & instantaneous turn of humanoid biped robot GENBE based on distributed control of physical body in a martial art, which uses only small active power with simple chaotic limit cycle utilizing instability. Furthermore, the simple autonomous shock avoidance during falling down and instantaneous rising of biped robot GENBE based on distributed control of physical body in a martial art utilizing instability was shown. Instability makes the natural movement and can be applied to walking of a physically handicapped person, rehabilitation, sports, and so on.

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The bottom of a person's foot grips the floor for balance, and the action force and action moment work at the foot bottom when he maintains posture and moves. A lot of equipment to measure the floor reaction force have been researched. However, no floor reaction force meter exists that can measure distribution information force in three directions. This paper aims at the development of a standing balance measurement system that exists from measuring instrument that distributed 6×4 three axis force sensors and software that displays and preserves the output of the sensor element. A time change of force that worked at the foot bottom is sought as vectors, and they are displayed with three-dimensional images whose data can be intuitively understood. The results of experiments demonstrate the effectiveness of the standing balance measurement system.

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It is necessary to establish an index for evaluation of fall possibility, because falls in elderly people lead to serious injuries. As the cause of falls is strongly related to the body balance ability, the purpose of this is to research the index to evaluate the fall possibility by using mesurement of body sway. Forty-six experienced and one hundred seventy-three inexperienced subjects of falls within the period of one year were mesured the body sway to research the relationship between experience of fall that is an index of fall possibility and the results on the analysis of the body sway. As the results, PL (AP) which was the average velocity of body sway on the direction of anterior-posterior and RD (ML) which was the average radial displacement on the direction of mediolateral showed significant higher value compared to the inexperienced one. On the comparison of age-related changes, PL (AP) showed the decline of balance ability with aging accurately. Through these results, it turned out that PL (AP) was the most available to evaluate the fall possibility.

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This paper presents a stability analysis of tandem riding on a motorcycle, focusing especially on the effects of the passenger's positional behaviors. Firstly we experimentally investigate the motorcycle and rider control behavior after a posture change by the passenger. This is done by measuring the motorcycle's responses to posture changes by the passenger during straight running at low speed. The results reveal some characteristic behaviors. Second, we construct a multi-body model for a human-motorcycle system for tandem riding. By comparing experimental and simulated results, we have confirmed the validity of the model. Finally, we conduct simulations on some situations in which passenger properties are varied, and obtain the effects of these passenger characteristics.

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The purposes of this study were to investigate the relationship between the relative tibiofemoral movement estimated with the point cluster technique and kinetics of the knee joint during normal walking, and to investigate relationships between the walking speed and the relative tibiofemoral movement or kinetics of the knee joint during prescript walking. Three cadences were made synchronous with three rhythms (Slow, Medium, and Fast) of the metronome during prescript walking. There were correspondences between three directions (Flexion-Extension, External-Internal, and Anterior-Posterior) of the tibiofemoral movement and directions of respective intersegmental forces and moments during stance phase. But there was not necessarily the correspondence through all of stance phase. Stable mechanism of the knee joint, so-called "screw home movement", was identified during three timings of the normal walking cycle. It was found that peak values of tibiofemoral movement and knee joint kinetics were increasing with increasing walking speed. These results suggested that changing the walking speed would influence tibiofemoral movement and kinetics of the knee joint.

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In this paper, we propose a new method and system for measurement of range of motion at shoulder joint. In rehabilitation and as part of health care, it is important to measure a motion of joint at several part of body. For measurement of range of motion at shoulder joint, there are many equipment and method in clinical place. Generally used as measurement equipment is universal goniometer. Because its system is analog method, measurement error is caused by reading difference of scale. In this study, we propose a system to measure range of motion at shoulder joint using three dimensional gyro sensor.

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The present study was conducted to investigate impact buffer property of a recently developed water penetration and retentive pavement for groundwork of artificial turf playground. Three balls with different weight and diameter were thrown down from 70cm height to three different groundworks of the artificial turf to evaluate the impact force and the coefficient of restitution. The groundworks were composed of two different hardness of water penetration (60 and 100%) and asphalt. The results obtained in the present study were as follows ; 1) The impact force of the asphalt groundworks was significantly higher than the water penetration and retentive clay pavements with different hardness of water penetration. 2) The coefficient of restitution of the asphalt groundwork was the highest among three groundworks. The clay pavement with 100% hardness was significantly higher than that with 60%.

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The purposes of this study were to design the concept the outer skeleton type of ergometer simulating the human muscular characteristics and to evaluate the exercise work load characteristics in wearing of this ergometer. The Hill's equation which approximated the relationship between force and velocity in muscular contraction was adopted for the ergometer as the human muscular characteristics. As the concept design of the ergometer, the human muscular simulating drum mechanism approximated following formula was developed ; ω={V_m/[Lcos(π/8-θ)]}={V_p/[rcos(π/8-θ)]} where Vm was torque as an exercise work load against the subject, L was diameter of the drum mechanism, r was length which sliders could move and Vp was the force the subject output. The experiment assuming in wearing this outer skeleton type of ergometer was done for evaluating the exercise work load characteristics against the subject using EMG. EMG was transformed to the integrated EMG. From this result, it was understood that the exercise work load was amplificated using this mechanism

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The purposes of this study were to develop the system for measuring the flexural vibration of a jump ski in actual ski flight and to measure and analyze the vibration using this system. To measure the flexural vibration of a jump ski in flight, two accelerometers were installed a ski. One was installed into the top of a ski, another was the tail of a ski. By means of accelerometers, vibrations of a ski were detected in actual ski flight. They were recorded to a data recorder and transferred to a computer, furthermore, transformed into the power spectrum by means of FFT. In experiment, an amplifier and a data recorder were inserted into a backpack wearing in a jump suit of a subject. The vibrations were analyzed in the following phases ; approach, take off, flight and landing. In approach, the natural vibration frequencies of a ski were not detected. The natural vibration frequencies were, however, detected immediately after take off. In flight, however, the natural frequencies were disappeared. Furthermore, in landing, the low frequency components between 40 and 70 [Hz] on the top of the ski were detected, because a jumper landed from the tail of ski. In addition, over 9800 [m/sec^2] of the acceleration amplitude at the top of a ski was detected.

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The purposes of this study were to set up of a bench simulator to simulate a flexural vibration of ski plate, and to investigate the relationship between the flexural vibration of a ski plate and human fatigue. To perform the first purpose, the flexural vibrations of the center of a ski plate in skiing and a grandeur in skiing and on tredmill were measured using accelerometers. It was found from the experimental result that the bench simulator using tredmill and the grandeur offered the simulation of flexural vibration of ski plate. To perform the second purpose, to investigate the relationship between the flexural vibration of a ski plate and human fatigue, the vibration simulating in skiing was loaded to a subject during 2 minutes by the bench simulator using a treadmill and the grandeur. In this measurement, surface EMG was measured and the mean power frequency (MPF) was calculated. The result indicated, vibration frequency increased, MPF decreased. This results led to the conclusion that flexural vibration of ski plate cause muscle fatigue of skier.

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It is made clear that one can simulate continuously a ski turn using a pair of skis on a horizontal snow surface. The simulation is carried out using a simulating approach proposed by the authors. In the simulation, an edging force and moment, and bending moment are directly added to each ski separately instead of a skier's ski control. The deflection and displacement of each ski, edging angle of each ski, horizontal reaction force acting to each ski from the snow surface during the ski turn are made clear.

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We desire to know the true three-dimensional absolute angle of an athlete's upper back while in vigorous motion. Much of the angle information can be obtained from a high-quality geomagnetic compass, provided the athlete is moving in an area with a straight magnetic field. Unfortunately the angle of rotation around the geomagnetic North direction cannot be detected by magnetic field sensors, and accelerometers cannot distinguish gravitation from acceleration, so at least one additional piece of angular displacement information is needed. In this paper we present a combined measuring method for the angle of a backpack worn by an athlete. With the athlete standing still, a triad of accelerometers measures the gravitational field and thus the true downward direction in the backpack reference frame. This is used to set the zero angle on two axes of a mechanical "vertical" gyroscope. During subsequent motion, rotation of the gyroscope axes is used to develop an incomplete quaternion, that is, one that does not account for rotation about the gyroscope rotor axis. A geomagnetic compass is used to develop another incomplete quaternion but this time with unknown rotation about the local Earth North vector. The unknown rotation axes could in principle align, but in practice this is easily avoided, so the two incomplete rotations can be resolved into a single quaternion representing the true absolute angle of the backpack. To illustrate the method, the design of the geomagnetic and gyroscope systems will be presented, along with details of the mathematics and an example of the measurement of a ski motion on a real ski slope.

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A new sensor for detecting a ski deflection and torsion during the actual ski turn on the snow has been developed. Bending sensors and torsion sensors are connected with beams to be formed a long sensor beam. The beam has been equipped on the upper surface of the ski though the central binding plate. The deflection of the ski is conformed from the bending angles of the sensors. The structure of the bending sensor is a pair of thin cross plates fit with strain gauges. The torsion in the forward region and that in the rear region are also detected by torsion sensors that have a structure that two tubes are connected with four thin plates. Deflection test and torsion test was made on the ski attached with the sensor beam to obtain the calibration factor for the sensors. The profile made from the sensor beam agreed well with the directly measured profile. On the other hand, commercial pressure sensors have been embedded on the other ski surface to detect the pressure distribution on the contacting surface with the snow. Measurement was carried out by a test player of Ogasaka company at Shiga kogen. The deflection and the torsion of the ski during the turn have been revealed with the movement on the ski trajectory and the applying force. Pressure distribution near the ski edge has been also measured along the turn trajectory and with the applying force.

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