1. Purpose The purpose of this study is to analyze ballet split jumps, focusing on the movement of the dancer's working leg and the way it affects the whole jumping motion. At the same time, we investigate how the movement of the working leg depends on the dancer's achievement level in classical ballet, comparing the jumps of dancers of different levels. 2. Methods The subjects are 14 women who have taken dancing lessons. We divided them into two groups: (1) Dancers at advanced level: 7 professional ballet dancers (=PD group); (2) Dancers at beginning/intermediate level: 7 students majoring in dance (=DS group). We asked them to execute two types of classical ballet split jumps: (1) grand jete=GJ; (2) grand pas de chat=GP. We videotaped their jumping motions with two video cameras. Our method of examination is three-dimensional kinematic analysis, using APAS (Ariel Performance Analysis System). 3. Parameters We obtained the following parameters: (1) displacement of center of gravity; (2) angle of upper body; (3) maximum knee flexion angle of supporting leg; (4) velocity of center of gravity. 4. Results In doing both jumps, PD group decreased the take-off velocity more than DS group. The jumping distance of PD group was shoter than that of DS group. The jumps of PD group are described as upward-moving or vertical, and those of DS group as forward-moving or horizontal. Using these parameters, we can summarize the results as follows: (1) The horizontal take-off velocity of DS group is greater than that of PD group in both GJ and GP. (2) The maximum displacement of center of gravity of PD group is higher in both GJ and GP. (3) The forward-bending angle of the upper body of DS group is greatest around the time of the maximum displacement of center of gravity. (4) The maximum knee flexion angle of the supporting leg of PD group is greater than that of DS group in both GJ and GP.

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喉頭の基本的な機能は喉頭を閉鎖することであり,閉鎖機能の1つに「息こらえ」(喉頭括約作用)がある.息こらえが上肢の運動支点を固定することになり,運動効率を高めていることは経験的に知られているが,十分な裏付けが得られていない。そこで,自己の体重を負荷としての上肢による負荷補償が最も要求される鉄棒運動の懸垂・支持回転系運動の中より後方支持回転系運動を取り上げ,2名の元一流体操選手を被験者とし,新たに開発された高解像度内視鏡ビデオシステムを用い,直接,喉頭の動態を観察すると共に,動作ならびに筋の作用機序の面より喉頭括約作用の運動への関与について検討した.1)2名の被験者共,回転動作時における喉頭動態ならびに筋放電様相は類似した傾向を示し,被験者間による大きな変異は認められなかった.2)後方支持回転では喉頭は回転中,終始開放されており,肩関節の動きに関与する筋群に顕著な放電の出現は認められなかった.3)しかしながら,後方浮支持回転では,喉頭括約(前庭ヒダ・声帯ヒダ閉鎖)が観察され,同時に肩関節の伸展・屈曲動作に関与する筋群に顕著な放電が出現し,肩関節での負荷補償が認められた.4)回転に伴う鉄棒の歪量の最大値は,後方支持回転よりも後方浮支持回転で大きく,しかも,その出現前後に後頭括約が観察された.これらのことより,鉄棒の後方支持回転系のような運動の場合,肩関節への負荷量の状態により肩関節伸展・屈曲筋群による負荷補償を支援するために喉頭括約作用が要求されるものと考えられ,上肢運動と喉頭括約作用との関係について,肩関節への負荷量の状態に起因する運動支援としての前庭ヒダ・声帯ヒダの関与の存在が強く示唆された.

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The purpose of this study is to evaluate the jumping smash technique in badminton from the viewpoint of conservation of angular momentum. Angular momentum estimates for the whole body were calculated, and the application of the principle of conservation of angular momentum was discussed for the smash motion. A cinematographic technique was used to determine the angular momentum of the human body about its mass center for general three-dimensional movements. The three orthogonal components of the angular momentum of 15 body segments, composed of a transfer term and a local term, were computed. The total angular momentum of the whole body was considered to be composed of the sum of the angular momenta of all body segments. Three-dimensional coordinates for determining the angular momentum were computed using Direct Linear Transformation method from film data. According to the principle of conservation of angular momentum,the smash motion is supported by the cooperation of all body segments. As the jumping smash movement is initiated, the lower limbs acquire some angular momentum on take-off from the ground, and then transmit it to the smashing arm. The torso and the left arm act as intermediaries in transmission of the initial angular momentum between the lower limbs and the swing arm. During the fore swing phase of the arm, a large angular momentum is generated by rapid arm rotation. The lower limbs and the head react to the arm swing with an equal and opposite angular momentum to keep the angular momentum constant. This kind of counter rotation to the smash arm is useful to keep the body balanced and reinforce the hitting arm. Key points in learning the jumping smash technique are to acquire an initial angular momentum on take-off and to create some counter rotation opposite to the swing arm.

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Some investigators have attempted to measure push-off forces in speed skating at different velocities. However, the relationship between the push-off forces and the skating velocity is still unclear because there is little information on the directions of the push-off forces and skating velocity. The purposes of this study were to develop a sensor-skate which could measure two components of force applied to the skate blade, and to investigate characteristics of the blade reaction forces on ice surface and their relationships to skating velocity. The sensor-skate consisted of a pair of sensor elements between the shoe and the skate blade to detect forces in both lateral/medial and vertical directions to the shoe sole. Linear regressions between the signals from the sensors and the forces applied were determined with different load conditions, and cross-talk from the lateral/medial force to the signal in the vertical direction was also calculated. Ten male speed skaters, including a world record holder at 1000m, served as subjects. At two different skating velocities, the force signals via strain amplifier were stored (100 Hz) in two data-loggers fixed on the skater's back. Blade reaction forces (BRF) in the coordinate system fixed on the ice were obtained by transformation of the force signals measured in the sensor-coordinates, based on the lean angle of the blade measured with VTR cameras (60 fields/s). Both vertical and horizontal components of BRF, point of BRF application and free moment about the vertical axis were calculated. The results obtained were summarized as follows: 1) Lean angle of the blade at the onset and end of the stroke were larger in fast skating (11.5±0.8 [m/s] ) than in slow skating (9.3±0.5 [m/s] ). 2) Peak value of the vertical component of the BRF was larger in fast skating than in slow skating. 3) Peak and mean of the horizontal medial component of the BRF were larger in fast skating than in slow skating. 4) Point of BRF application at the end of the stroke was located further forward in fast skating than in slow skating. 5) Peak magnitude of the free moment of internal rotation about the vertical axis was larger in fast skating than in slow skating. The onset of the horizontal medial component of fast skating was much earlier in the world record holder than in the other subjects.

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It is well known that the leg movement in sprinting is closely related to sprinting velocity for instance, the swinging back velocity of the leg just before the touchdown. Although some suggestions for improvement in leg movement are proposed based on these relationships, it is not easy to improve leg movement only by these suggestions and verbal instructions, because of differences in the interpretation of verbal instructions and conscious emphases of sprinters. The purposes of this study were to clarify the changes in the leg movement under the conditions of various conscious emphases of the leg movement in sprinting and to examine the causes of the changes through the simulation technique. Eighteen male sprinters of the varsity club served as subjects in the experiments. Two-dimensional leg movements of their sprints were recorded with a high-speed video camera. Sixteen kinematic parameters of the hip and knee joints were selected and analyzed in relation to sprinting speed. Three parameters related to the speed were extracted: the maximum flexion angle of the hip, the flexion angle of the knee at the touchdown (TD), and the angular velocity of the hip extension at TD. Five of the subjects in the above experiment were asked to emphasize the leg movements consciously and to sprint as fast as possible. Leg movements emphasized were (a) quick recovery of the leg after the toe off (TO), (b) quick knee flexion after TO, (c) quick swinging back of the leg before TD, and (d) high knees, which were usually used in coaching sprinting. Two-dimensional leg movements recorded in the same manner were compared with the movements peculiar to each subject which were obtained in the first experiment. In the "high knees" condition, it was found that the mean value of the maximum flexion angle of the hip did not increase significantly although increases in the maximum flexion angle of the hip were expected. The changes in the parameters in other conditions were not always the changes expected from the verbal instructions. In addition, simulations of the leg movements during the recovery phase were carried out based on a link segment model in order to examine the reasons why the changes in the leg movements were not uniform. The results of the simulations revealed that changes in the leg movements were affected not only by the magnitude of the changes in the joint torques but also by the timing of the changes of the joint torques. It was also found that the larger knee flexion torque caused the slower knee flexion velocity at TD in the certain condition of the simulation. In conclusion it was suggested that the instructions on the leg movements in sprint were considered and to be suitable to the individual of the sprinter, especially joint torques patterns.

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The amplitudes of stretch reflex components are known to be modified according to voluntary movement. Specially, the change in long-latency reflex (M2 component) is bigger than that in spinal stretch reflex during voluntary activity. Therefore it has been considered that the M2 component is related to motor control, and it has been assumed that the change M2 component in motor control changes for the purpose of movement. However, it has not been, studied experimentally whether degree of change in M2 component causes functional differences in muscle tension output. The present study was conducted to investigate what effect the M2 component during reaction movement of wrist flexion or extension had on those movements, and to clarify the degree to which modulation of long-latency activity played a functional role in movement performance. Seventeen healthy men, ranging in age from 20 to 28 participated in the study. A DC torque motor was used to generate sudden angular displacements in the extension direction at the right wrist joint. Analysis of the averaged surface electromyogram recorded from the wrist flexor muscle showed that short- and long-latency reflexes (M1 and M2 components) were evoked by muscle stretching. The results are summarized as follows: 1) The M2 amplitude from flexor muscle was increased during reaction movement in the flexion direction, and decreased in the extension direction conversely. In short, the long-latency reflex activity was task-dependent. 2) In flexion reaction task, the bigger the M2 amplitude was, the smaller the handle movement which was drived by torque motor in the extension direction became. Consequently, there was negative correlation between the increase of M2 amplitude and the shortening of flexion motor time in movement performance. 3) In extension reaction task, smaller M2 amplitude led a faster handle speed in the extension direction. Consequently, there was positive correlation between the decrease of M2 amplitude and the shortening of extension motor time in movement performance. These results reveal that a change of the M2 component is closely related to motor control with supraspinal pathways, and movement performance is subject to the degree of modulation of long-latency activity. This seems to suggest that a change in the long-latency reflex has a functional effect on the voluntary muscle tension output in the initiation of movement.

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The force-length relation of muscles is one of the basic mechanical properties. However, there have been few reports about the relationship between joint angle and torque for a human upper extremity. The purpose of this study is to determine the relationship between joint angle and isometric torque of human upper extremities. A nonlinear model (neural network model) is used to estimate joint torque under the restriction of constant muscle activities. Three normal volunteers were seated in a chair and put their upper extremities on hanging plates which were allowed to move freely on the horizontal plane. External force was applied to the wrist with a string, tied to their wrist, with a weight. External force was 0, 2.5, 5, 7.5, 10, 12.5 [N]. Subjects were instructed to maintain their upper extremity at a target joint angle and to balance against the external load with minimum effort. Target shoulder joint angle was 30°, and elbow joint angle was 30°, 35°, …, 100°. Five-channel integrated EMG (IEMG), joint angles, and torque were recorded for 5 sec. Elbow and shoulder joint angles were calculated by detecting positions of infrared LEDs attached on the upper extremity of a subject with a 3D motion analyzer (OPTOTRAK, Northern Digital Inc.). Surface Ag-AgCl electrodes taped to the skin were used for bipolar EMG recording. Five-channel EMGs were recorded from caput longum muscle biceps brachii, caput laterale, muscle triceps brachii, muscle pectoralis major, and muscle deltoideus. IEMG was obtained with a differential amplifier, a rectifier circuit, and a second-order low pass filter. External force was measured with a strain gage. Elbow and shoulder joint torque were calculated geometrically from joint angles, and arm length, and the external force. The neural network model consists of an input layer of 7 units, one hidden layer of 6 to 15 units, and an output layer of 2 units. The inputs were 5ch IEMGs and both elbow and shoulder joint angles. The outputs were elbow and shoulder joint torque. After learning, elbow joint torque was estimated where 5ch IEMGs were fixed and only elbow joint angle was varied. Estimated results were as follows. Torque of the elbow extensors monotonically increased as flexing of elbow joint. However, the torqueangle relation of flexors had a peak at about 90°. These relationships were discussed by considering the dependence of muscle force on the muscle length, as well as the angle dependence of moment arms and muscle length of the elbow flexor and extensor muscles.

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The in vivo analysis of bioelectric and biomagnetic potentials supplies valuable information for localization of current source. Only a few attempts, however, have so far been made at inverse analysis of surface EMG. The purpose of this study is to estimate functional and structural parameters of the motor unit (MU), e. g. depth and strength of the current source through the inverse analysis of surface EMG. Circumferential distribution of motor unit action potential (MUAP) on the skin surface was measured with a surface electrode array which was composed of 16 bipolar contacts. One-dimensional (circumferential direction) potential distribution at the peak time of MUAP and two-dimensional (circumferential direction and time) potential distribution were obtained by averaging of recorded surface EMG. The averaged potential was compared with the potential calculated by a model of current dipole propagating along the muscle fiber. In the model calculation, the depth, strength and position of the current source, conduction velocity (CV), and electrical conductivity were treated as unknown parameters and determined by minimizing the difference between the measured and the calculated potentials. The minimizing calculation was executed by Simplex method. The estimated depth of the current source was 1-6mm from the skin surface. Cross-sectional size of the motor unit estimated by the circumferential potential distribution was consistent with the results of measurement by multiple contact needle electrode and of histochemical experiment. Distribution in muscle fiber direction of the neuromuscular junctions belonging to single MU was estimated to range from 3mm to 15mm. If CV of MUAP and electrical conductivity of muscle are obtained by experiment or inverse analysis, we may estimate more accurately the depth, strength and size of the current source. Furthermore, in order to consider inhomogeneity and anisotropy of muscle tissue and boundary condition, we have to use numerical analysis tools such as finite element method.

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Although many studies on the tensile characteristics of the cruciate ligaments, especially of the anterior cruciate ligament (ACL), have been performed, the differential function and the length patterns of the ACL fibers are still controversial. It is not possible to determine the strain of the whole ACL, because the entire ligament cannot be loaded uniformly due to the complex movement of the insertions. Thus the non-uniform distribution of strain on the fibers within the ACL has not been fully studied. The objective of this study, as the best alternative to the in vitro measurements to date, is to theoretically analyze the change in shape and stress distribution over the entire surface of the ACL when its insertions are moved in three dimensions associated with knee flexion, thereby obtaining the verification of our previously performed experimental results for a pseudo ligament (rubber material). Stress analyses were carried out using the finite element method for an incompressive hyper-elastic material. The nonlinear stiffness relation between the node force and the node displacement for a triangular element was introduced. The Newton-Raphson method was used to solve the nonlinear equations associated with finite element representations of the pseudo ligament. The previous measurement and the present theoretical results were in good agreement. The results included graphic representations for three-dimensional deformation of the ligament associated with knee flexion. The unique advantage of our simulative study was that strain at every point could be obtained over the entire surface of the ligament as opposed to localized strain in specific bands of the ligament. Special attention was paid to the distribution of longitudinal strain as a function of the knee flexion angle. The results demonstrated that strain distribution varied, even along the fiber run, and large strain gradients were observed in the regions near the bone attachments. It was found that distance between insertions introduced serious discrepancy from length along a curved fiber. Variations of strain distribution for anterior-posterior displacements of the tibia were obtained in our simulative study. The net resultant force at the tibial insertion of the ligament was calculated as well.

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The impact that occurs when the heel strikes the ground causes some problems in athletes and patients. Strong impact forces may damage or degenerate joints. The cushioning effects of soft tissues of joints or muscles around a joint have been studied experimentally. The configuration of the leg landing on the ground has also been found to be important in absorbing the impact force. The impact force at heel contact with the ground was evaluated using accelerometers (Nihon Koden, 1.7g). The accelerometers were pretested on human cadavers to determine the relationship between the skin-mounted accelerometer output and the bone surface acceleration. The acceleration of the bone was measured by the accelerometer mounted on a screw (1.7g, 2.5cm long). The screw was inserted into the bone. The impact force transmission through the bone up through the human body was measured as the acceleration by both accelerometers. They made little difference. So the reliable acceleration of the impact force through the bone could be obtained noninvasively by the skin-mounted accelerometer. The experimental results for normal walking (100 step/min) were obtained in two cases: with subjects' ankle joints free or were fixed using an ankle brace. The results showed that the transfer of acceleration of impact force to upper joints was attenuated greatly at the ankle and knee joints with normal and fixed-ankle walking, respectively. Passive impact forces in the vertical reaction were also measured to examine relation to the acceleration at leg joints. The leg configuration just before it strikes the ground was discussed using a planar model. The model has five massive links, in which the feet were assumed to make a point contact with the ground. Then the model having the feet was introduced to examine the function of a foot. A convenient method was proposed to represent the relationship between the velocity of the foot just before striking the ground and the impact force by a contact with unit velocity of 1.0m/s. The model with the feet reduced the impact remarkably, in agreement with the experiment. And the magnitude of the impact simulated depended on the leg configuration at the heel contact: an extended knee made the impact great; some flexed knee reduced the impact and minimized the force. Physical parameters of the model were chosen based on normal persons.

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In the analysis of human movement, it is significant that appropriate parameters of the inertia property of body segments should be used because they will affect various computed kinetic variables. When analyzing the movement of elderly people, it is also desirable to use the inertia parameters of the body segments suitable for the elderly. Although there are appropriate sets of inertia parameters of the body segments for children (Yokoi et al., 1986) and young adults (Ae et al., 1992) of Japanese, no report exists on those for Japanese elderly. The purposes of this study were to determine the mass, the location of the center of mass (CM) and the principal moments of inertia about three axes of the body segments for Japanese elderly males and females by using an elliptical zone model (Jensen, 1978; Ae et al., 1992), and to develop a set of regression equations to estimate inertia parameters of the body segments using simple anthropometric measurements as predictors. Subjects were 90 Japanese elderly males aged 62 to 86 yr. (mean 75.1 yr.) and 89 Japanese elderly females aged 61 to 83 yr. (mean 73.0 yr.). Each subject, wearing swimming suit and cap, was photographed in a standing position in the measurement frame with a thin mirror mounted at an angle of 45° to the subject. Body segments were the head, whole torso, upper arms, forearms, hands, thighs, shanks, feet, upper torso and lower torso. They were modeled as a stacked system of elliptical zones 2cm in thickness. Segment density was assumed to be uniform and selected from 26 sets of segment densities after Dempster (1955) and Chandler et al. (1975). The mean errors in the estimation of total body mass were -0.07±0.54% (maximal error: -2.03%) for the males and -0.01±0.45% (maximal error: -1.27%) for the females. Equations for the estimation of the body segment inertia parameters were determined using a stepwise multiple regression with age, standing height, body weight and segment length as predictors. The results obtained could be summarized as follows: 1) There were significant differences in many body segment inertia parameters between the elderly males and females. The percent mass ratios of the forearm, hand, foot and upper torso for the elderly males were significantly larger than those for the elderly females, but the thigh, shank and lower torso ratios for the elderly females were significantly larger than those for the males. 2) There were significant differences in many body segment inertia parameters between the elderly and the young adults (Ae et al., 1992) and between the Japanese elderly and the Canadian elderly (Jensen et al., 1993; 1994). 3) The correlation coefficients between the body segment inertia parameters determined and estimated from the regression equations were all significant (0.328-0.979; p<0.01). The equations determined in this study should be valid for estimation of the body segment inertia properties for Japanese elderly.

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This paper describes consideration of the capable head movement of a child severely disabled with cerebral palsy who can't speak or control her extremities. This consideration aims to be able to operate a couple of switches for some augmentative and alternative devices. Now, she can only express her intention, "yes" or "no", only by her head movement to the right or the left, and only while she is supported by her mother. First, this head movement was measured by using an ISOTRAK system which can measure a three-dimensional position and the Euler angles. As a result, small movements to the left (identified as "left?") were found in addition to normal movements to the right and the left. In consideration of the helical axes and dynamic energy, it can be said that the normal movements were made possible by positive utilization of gravity, while the small movements (left?) occurred because she couldn't utilize the gravity when she tried to move her head to the left. Next, a seating system to facilitate head movement without her mother's support was developed. This decreased the physical burden on her mother. In addition to body support, this system also has the function of buffing the involuntary extension movement of her body. The backrest was separated into 3 segments which were respectively fitted to her head, chest and pelvis. Each segment was connected with an elastic pin joint so that, if she extended her body, the backrest would lean backward following her movement; if her extension became weaker, the backrest would return to a normal position at the effect of the joint's elasticity. In this way, her sitting posture remained stable. Then, her head movement on this seating system was measured by using the ISOTRAK system. As a result, when she kept her head nearly straight forward, she could push the right and left switch. And it became clear that she rotated her neck during these movements. These were different from the movements made with her mother's support. The rotation movement was considered an efficient action which was caused by reducing the effect of the friction between her head and the headrest. Moreover, it is found that a large movement to the left or the right disturbed her effort to return her head to a medium position. While her head returned from far right position with difficulty, the potential energy increased before this action. So, it is considered that gravity is very effective even with the seating system. Therefore, it is important to cautiously set up the seating position related to gravity, such as the tilting angle, headrest position and so on. As a result of this study, the possibility that this child can use augmentative and alternative devices by herself was suggested.

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For reconstruction of anal function in fecally incontinent patients, it may be feasible to transpose the gracilis muscle around the anal canal, using electrical stimulation to trigger contraction. However, because the fast-twitching gracilis muscle is incapable of prolonged contraction without fatigue, it is necessary to convert it to a slow-twitching, fatigue-resitant muscle. When the muscle contraction decreases even transiently between stimuli, the neoanus cannot maintain continence. Thus, the muscle must retain some tension between each stimulus. To fulfill these criteria, the neoanal sphincter must be stimulated at a frequency that can include sufficient summation. We demonstrated this conversion and contractile summation by long-term electrical pulse stimulation (0.2 msec pulse width) at low frequencies using a rabbit model. The nerve to the gracilis muscle of rabbits was continuously stimulated at 2Hz, 5Hz and 10Hz for 2 to 8 weeks. This conditioning reduced the frequency necessary for summation; the muscles conditioned at 10 Hz for 6 or 8 weeks induced sufficient summation (fusion index>90%) at 20Hz, and also showed sufficient summation (fusion index=80%) at 15Hz, a frequency that produced muscle contraction without fatigue. The conditioning also prolonged twitch contraction time and half relaxation time for one-shot pulse stimulation, but the twitch contraction speed was reduced with conditioning at a frequency greater than 5Hz. In the 6-week conditioning group, the percentage of type I fibers, identified by ATPase staining method, increased as the conditioning frequency became higher and the conditioning period became longer. After assessment of the conversion of gracilis muscle to a fatigue-resitant muscle, transposition of the muscle around the rectum was performed in Japanese white male rabbits. The muscles conditoned at 10Hz for 6 weeks were stimulated at 15Hz, a low frequency to permit prolonged contraction, and the neoanal pressure increased maximally to more than 100cmH_2O. The pressure suitable for fecal continence maintained in a period longer than 10 weeks (maximally 38 weeks) without any trouble, while the non-conditioning group showed decay of neoanal pressure in a short period. The conditioning made it possible for the rabbit's gracilis muscle to create anal pressure with a sufficient rise in the basal pressure at a frequency permitting prolonged contraction. Thus, we concluded that conditioning at 10Hz for 6 weeks can convert rabbit gracilis muscle to a slow-twitching, fatigue-resitant muscle and produce enough summation at a low frequency stimulation to permit prolonged contraction suitable for a power source to reconstruct a neoanal sphincter.

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In the field of biomechanical modeling, many kinds of studies of the musculoskeletal systems have been made to estimate the muscular force of the extremity in a specific motion. However, the mechanics of a wrist movement have barely been investigated for defining and modeling the muscular dynamics in a clinical use. And the results from the model often conflict with the experimental results in vivo. This is because the wrist joint models used in the studies are oversimplified without using kinematic and anatomical information such as the axile position, the muscular moment-arm, etc. The purpose of this study is 1) to estimate the axile position of the wrist joint and the momentarm of forearm muscles experimentally and 2) to give the kinematic and graphical data on the wrist joint that is useful for building a musculoskeletal model. In this paper, the method of calculating the 3-dimensional axile position from the measurement of a rigid body motion is applied to estimate the axile position of the wrist joint during flexion/extension. The hand motion relative to the forearm is measured with an electromagnetic tracking system (3SPACE ISOTRAK, Polhemus USA). A specific circular motion is used to confirm the sensitivity of the measuring system to calculate the axile position. The experiments are performed with 5 kinds of load to the wrist joint (no load, 0.1, 0.05kgm anterior/posterior load). The moment-arms of ECRL, ECRB, ECU, ED, EPB, FCR, FCU, FDS, FDP and FPL are evaluated with the results of the axile position and the muscular lines are measured with 3 kinds of wrist joint angle with MRI. The wrist joint axis during flexion/extension is in the range of about 10mm square, at the proximal and anterior part of the lunate. The axile position changes within the range according to the movement and the direction and the magnitude of the load, but the axis falls at almost right angles to the movement plane. The movement of the carpal bones during flexion/extension are measured with an X-ray video camera to substantiate the results of the axile position. The results of the measurement-that the mid-carpal joint mainly moves during flexion and the radio-carpal joint mainly moves during extension-make it manifest that the axile position changes distally and proximally. From the experimental results it is found that the moment-arm of the extensor becomes larger with the load in the anterior direction, and the same is true for the flexor with the load in the posterior direction. The moment-arm of each muscle is a key parameter to relate the joint torque with the muscular force, and also the joint motion with the muscular length. The moment-arm in this study may be used to estimate the forearm muscular length in the modeling analysis of the wrist joint motion. The muscular length is one of the important indices to consider the muscular dynamics investigated physiologically and anatomically. And the musculoskeletal model including this information will be very useful for estimating a practical stimulation pattern of the functional electrical stimulation system.

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In the present paper, coordinating functions among antagonistic pairs of the mono- and the bi-articular muscle in the human upper extremity were analyzed in terms of electromyographic (EMG) kinesiology, and control properties of a two-joint rink model equipped with an antagonistic pair of bi-articular muscles were analyzed experimentally as well as theoretically. EMG studies: Subjects employed were 5 healthy young male adults, and muscles tested were deltoid anterior (Da: f_1) and posterior (Ds: e_1) portions, brachialis (Br: f_2), biceps brachii long head (Blo: f_3), and triceps brachii lateral (Tla: e_2) and long (Tlo: e_3) heads. EMGs were recorded during isometric arm push and pull movements in all directions (360°) with maximal effort in the sagittal plane. All round force directions were divided into six ranges with three crossing lines at the wrist joint (W). Directions b and e were pushing up and pulling down along the forearm, and directions c and f, pulling up and pushing down, respectively, parallel with the upper arm. Directions a and d were passing through shoulder joint (S) and point W. All subjects showed almost the same EMG patterns, where the Blo and the Tlo reversed their activity levels in the ranges between a and b and between d and e, the Da and the Ds, in the ranges between f and a and between c and d, and the Br and the Tla, in the ranges between b and c and between e and f. Thus, two pairs of the antagonistic mono-articular muscles as well as the pair of bi-articular muscles showed crisscross activity patterns in each pair of the opposing ranges. In the other ranges than the opposing pair of ranges where the criss-cross patterns appeared, one muscle of the antagonistic pair of mono- as well as the bi-articular muscles showed full activity level and the other antagonist of the pair showed almost nothing. This essential activity pattern never changed even though angular distributions of the ranges of force directions changed widely with the postural changes. The model analyses: 1) Based on the EMG results, coordinating patterns of contractile forces exerted at the muscles incorporated on the model were postulated as follows: uf_1+ue_1=100%, uf_2+ue_2=100%, uf_3+ue_3=100%. Distributions of the maximum forces developed at the end point of the model were very similar to the one obtained in the human experiments. 2) The shape and inclination of the stiffness ellipse exerted at the end point of the model can be controlled independently in the model with the bi-articular muscles, but they cannot be controlled independently without the bi-articular muscles. Effects of forces applied at the end point of the model from outside were examined theoretically as well as experimentally. The end point can be moved along the direction of the outside force in the model with the bi-articular muscles, but the end point moved in the shifted direction away from the outside force in the one without the bi-articular muscles. A robot with these properties could control its position, force and stiffness without a complex and hard robot controller, and these properties will be useful to an assembly robot, human-friendly robot, orthotics or prosthetics.

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The feasibility of a self-organized change of stretch reflex gain caused by the passive change of the ankle joint angle was discussed in the human soleus muscles. The amount of the maximal amplitude of Hoffman (H) reflex, normalized by the maximal direct motor (M) response, was used to evaluate the excitability of the soleus motoneuron. The H reflex amplitudes in 1) normal standing, 2) ten degree dorsiflexion, 3) ten degree plantarflexion, were measured in standing posture, and also in sitting posture with the same ankle joint angles, in ten neurologically intact subjects. The normalized H-reflex amplitude was decreased from 38 percent to 32 percent by dorsiflexion and increased to 44 percent in sitting posture. The amplitude in standing posture was also decreased 41 percent to 39 percent by dorsiflexion and increased 42 percent by plantarflexion. It was suggested that the motoneuron pool is inhibited by passive dorsiflexion and facilitated by passive plantarflexion. In 24 of the 30 inhibition by dorsiflexion was indicated in sitting posture; however, only 17 indicated the inhibition in standing posture. In 25 of the 30 facilitation by plantarflexion in sitting posture was indicated; however, only 16 indicated facilitation in standing posture. The tendency of the inhibition and facilitation was obvious in the sitting posture but not clear in the standing posture. Therefore, the change of the reflex loop gain appears to have no relation to the higher center control system such as that for postural control, and seems to be a local self-organized adaptation. Two hypotheses were proposed: 1) in feedback gain compensation, the change is for compensation of the muscle spindle sensitivity change, 2) in stiffness compensation, the change is for compensation of the nonlinearity of the joint stiffness. Measurement of the response to the mechanical perturbation is required to obtain answers for these hypotheses.

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In human forearms, the radius and the ulna are geometrically regarded as a combination of two spirals arranged in parallel, which rotate in opposite directions. I assume that the optimal curves for these spirals are geodesic curves on a surface of a cone, expressed as a formula as follows: [numerical formula] [numerical formula] [numerical formula] γ: the shortest distance from the vertex of the cone to the geodesic curve. [numerical formula], where φ is the vertex angle in developed plane of the cone. When two geodesic curves exist on a corn, the curve which is obtained by proper prolongation or reduction of one curve proves to be homothetic to the other. And all geodesic curves on a corn are symmetrical when they are prolonged to the proper extent. It is interesting that this symmetric formula is a common characteristic of hard tissues of animals. Furthermore, it seems that these geodesic curves exist in several hard tissues of many animals, as well as in humans. When two geodesic curves rotate with rolling contact at one point and at a constant angle between tangent planes of two-geodesic curves, the distance between the vertexes of two cones is kept constant. Using this geometric concept of geodesic curves on the cone, I designed a model of forearm movement. In this model, the humeral capitulum and the mid-point of the axis of the humeral trochlea are regarded as the vertexes of two cones. The above-mentioned hypothesis proposed the novel concept that morphology and functions can be generalized under the identical geometric theory with the geodesic curves on the cone.

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From what sort of animal and in what process did humans obtain bipedal locomotion through evolution? This is the most fundamental question still left to us for understanding the origin of hominid bipedalism. Recently, in considering prehabitual locomotion, the brachiation model and vertical climbing model have become leading theories. However, these proposed models do not explain why the body proportions of man and modeled living brachiaters or climbers are so different in terms of the intermembral index. In this study, we analyzed several types of human bipedal and quadrupedal walking with different intermembral indices. The intermembral index was changed using a prosthesis (1 kg) which can elongate the arm from 70% to 140% in 10% steps. Bipedal walking of an ape, which is characterized by an inclined body and flexed knee joint, was imitated by human subjects. In quadrupedal walking, the knee joint was rather extended like that of a monkey. We also analyzed climbing motion on a ladder as a substitute for vertical climbing. The height of the experimental ladder was 4.2m, and the width 80cm. The distance between each step is 10cm, so that a subject could freely place a foot on a nearby step. To detect vertical and horizontal forces on feet and hands, force sensors were attached to 10 steps partially up the ladder. These walking and climbing motions were measured three-dimensionally by two sets of position detector cameras. The musculo-skeletal model was composed of 7 rigid segments-thigh, shank, foot, upper arm, forearm, and head-torso segments-and 9 principal muscles in each lower limbs. Model parameters such as mass were adjusted to each experimental subject. Some evaluative indices for the joint motions and muscle activities were defined by magnitude and pattern, so that we can quantitatively compare the similarity to erect bipedal walking. Calculating the distance of the indices from erect bipedal walking, we obtained the following results: 1) Quadrupedal walking enhances the development of knee muscles. 2) Vertical climbing improves ankle extensors and the kinematic potentiality of each joints. 3) Ape-type bipedal walking strengthens the muscles around the hip and ankle joints. 4) The intermembral index, which changes from quadrupedal walking to ape-type bipedal walking, and subsequently from ape-type bipedal walking, to erect bipedal walking is about 110 or 140. Therefore, we conclude that the change toward bipedal walking occurred in primates with long upper extremities, and that vertical climbing assists the change from quadrupedal to bipedal walking mechanically as well as kinesiologically. This conclusion, which proposes that primates with longer upper extremities were more capable of changing toward bipedalism, does not contradict the brachiation model. Moreover, those who keep their bodies away from trees (ladders) have more potential ability for bipedalism; this also shows the adaptability of primates with long upper extremities as our ancestors.

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Masticatory force and biting force applied to the teeth are shown experimentally to generate compressive force to the temporo-mandibular joint (TMJ). This force is referred to as "temporomandibular joint load". Normal TMJs are both tolerable and adaptable to a certain amount of load, although excessive loads are believed to be a cause of TMJ dysfunctions. Thus, TMJ load can be considered to be controlled to a certain extent by the stomatognathic system, so as not to exceed a certain limit. In order to clarify the amount of load applied to the TMJ, the magnitude and direction of TMJ load have been estimated intensively under various biting conditions, employing a static equilibrium analysis. The controllability of TMJ load, however, has yet to be investigated sufficiently, due to the difficulty of manipulating various model parameters. To simplify this analysis, we employed a two-dimensional jaw model incorporating three masticatory muscles, masseter (assumed to include internal pterygoid), the anterior portion of temporalis, and lateral pterygoid, which function dominantly during biting. We determined the location, the orientation and the magnitude of muscle forces of our model, employing morphological and electro myographic data reported previously. Biting force is assumed to be applied solely to the first molar. We carried out two distinct experiments to obtain TMJ load: 1) under various magnitudes of force on each muscle, and 2) under various directions of TMJ force, while other model parameters are all fixed. Experimental results indicated that the anterior portion of the temporalis can generate biting force without amplifying the magnitude of TMJ load, and additionally can control the direction of TMJ load. This load was clarified, for the first time, to be minimized when it points in a certain direction, under the condition of a fixed biting force. This direction corresponded to that anatomically optimum to support compressive forces, and was independent of the direction of biting force. It was also verified to be reduced by applying biting force somewhat antero-inferiorly. These results suggest that TMJ load can be considered to be controllable by coordinated activities of masticatory muscles.

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The object of this study is to conduct mechanical evaluation judgments of the ability of people to maintain balance in a standing posture. The authors developed a system which swings a plate on which a person is standing and measures the resulting plate torques and the angles of inclination of each part of the body element at that time (Posture Control System). This swing generator generates smooth rolling and pitching movements, and the movement cycle and direction can be changed freely with an N. C. controller. As a major characteristic of this system, changes of balance caused by swing disturbances such as changes of torque acting in the plate can be measured. This actuator (blush less servo motor) is used not only to generate motions but to serve the function of torque sensor. Small torque balance inclinometers are used to measure the angles of inclination of each part of the body (12 sections). Moreover, a tri-dimensional model of the body is constructed to calculate the center of gravity and center of force operating in each part of the body. In this report, the authors used this Posture Control System and tried the following: 1) Evaluation of ability of normal healthy old people to maintain balance in a standing posture by torque of the sole. 2) Evaluation of learning phenomena by fuzzy linear regression analytical methods for general evaluation of standing ability. Tests of evaluation of the traceability were conducted with normal young healthy people as well as with normal old healthy people as subjects. Tests under the same conditions in which people swung the plate while standing on two legs showed the following characteristics. In the old people, width and standard deviation of delay for distance (dθ) were large, and the average of dθ was large in the negative direction. The old people fell far below the young people in traceability of balance for a change of swing direction. Moreover, for individuals with unknown functional disorders, learning phenomena are discussed in the framework of possibility; the authors employed the fuzzy regression model to analyze learning phenomena. This approach enables us to understand two characteristics of the learning effect. One is the formation of competence at swing disturbance. The other is stability. For example, young and old people are much the same at the formation of competence. But the old people are inferior to the young in stability. In rehabilitation training, the results of training can be expected in the future as each handicapped person has his own aim. It is considered a useful application to conduct a measuring experiment for many subjects and to change the results into a data base in this system.

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In order to measure the movement of players or of a ball in field sports (soccer, rugby, etc.), it is necessary to measure them in a large field at a high resolution. If players can know about their movement or the trajectory of a ball quickly, it would be helpful for the training. Thus, real time measurement is also needed. We have been developing an optical measurement system. For this purpose, a slit beam is scanned at 360Hz by rotating a polygon mirror. A linear position sensing device (PSD) is used to detect the reflected light from objects. Horizontal position is calculated by determining the exact time of reflection via correlation filter and interpolation method. Vertical position is calculated by (sum output)/(diff. output) of PSD. By synchronizing two unit of this system, 3D position of objects is determined. 3D position of 11 objects can be calculated in real time (<2.78ms) by a high-speed processor (composed of a DSP and a transputer). Horizontal position error is attributed to the following. 1. Flicker of Xe-gas in a lamp. 2. Long-term and short-term fluctuations of angular velocity of the polygon mirror. The error caused by the second factor could be removed by means of some compensation. A slight inclination of vertical axis of the polygon mirror was found to cause vertical measurement noise. This was removed by offsetting the effect of vertical fluctuation of the optical path over one turn of the mirror. Aspects of the measurement system are as follows: Measurement distance: 13.5m〜30m Field of view: Horizontal 48° Vertical±4° over a optical axis Resolution: Horizontal 0.06mm at 13.5m distance, 0.59mm at 30m Vertical 0.37mm (13.5m), 11.7mm (30m) on the optical axis.

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A microcomputer-based ambulatory monitor has been developed. This monitor utilizes a CMOS one-chip microprocessor (Toshiba Z 84 C 015-10), which has an Intel Z 80-compatible 8 bit CPU, two 8-bit parallel I/Os, four 8-bit counter/timers, and a fullduplex serial I/O. A general purpose min/max detector circuit has been designed to detect minimum and maximum values of a single-channel cyclic analog signal correlated to human gait. The analog signal fed to this circuit is converted to two logical pulses the width of which is proportional to the minimum and maximum values during one gait cycle. A logical signal which represents the gait cycle is also generated. These three logical signals are connected to three signal lines of a parallel port. Clock pulses of 100Hz and 10kHz are also generated and connected to three counters which convert pulse width or pulse cycle of the logical signals into corresponding digital representations of minimum, maximum, and cycle time of the gait-associated analog signal. The digital representations of 8,000 gait cycles can be stored in 32kbyte RAM, and retrieved from serial port via RS232C interface at a request from any host personal computer. The min/max detector circuit is assembled with DIP ICs, and contains a one-chip microcomputer, other peripheral circuits and a 006 P 9[v] battery, in a plastic box measuring 140(W)×80(H)×40(D)[mm]. The weight of the total monitor box is 120g. As one application of this ambulatory monitor, measurement of stride length and walking velocity was attempted. The absolute segmental angle of the thigh of one leg in the sagittal plain was detected by a piezoelectric gyroscope attached to the top of the knee. The angle signal was fed to the min/max detector circuit. Stride length was estimated from the absolute of this segmental angle by utilizing a simple mathematical model of biped locomotion. Walking velocity can be calculated from stride length and cycle time. The accuracy of the stride length and walking velocity was evaluated for 8 normal female, 11 normal male, 3 hemiplegic, and 3 A/K amputee subjects. The result was promising. Possible applications of this ambulatory monitor for assisting clinical decisions on patients with gait disabilities are discussed.

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A general method to get the best alignment of trans-tibial (BK) prostheses was analysed on the basis of mechanics and it was concluded that useful information is supplied by a system which can display mechanical quantities (forces and moments) exerted on a trans-tibial prosthesis in real time. From this viewpoint, a system containing a pylon load cell installed in the shank of the prosthesis to measure six quantity forces, flexible electro goniometers made of electroconductive rubber placed on the side of ankle and/or knee joint, and a portable data processing subsystem was developed. The whole system weighs less than 10kg, and is movable anywhere. From the output of the transducers, the load line on which the resultant force and moment work and are parallel to each other is calculated and displayed on the graphic plane of the micro computer in real time. With this system, prosthetic alignments and prosthetic functions were measured and evaluated. The load lines in standing posture and in level walking were measured and compared with the process of aligning a trans-tibial prosthesis by some skilled prosthetists on the same amputee. After each stage of bench, static and dynamic alignment, load line shows a peculiar pattern of its own. The resultant moment (torque on the load line) tends to decrease from bench to static and from static to dynamic alignment. The stance phase control function of a prosthetic knee joint was measured in a trans-femoral (AK) amputee for level walking and ramp descent. The amount of knee braking on stance phase was set in the three positions of free, normal and lock. With the knee braking mechanism working, load line comes to pass behind the knee axis in level walking. In ramp descent, more significant phenomena were observed compared than in level walking. From the real-time display of the load line acting on the prosthesis, problems of static alignment, dynamic alignments and functions of joints will be made clear and the way to get better alignment and better function can be easily estimated.

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The purpose of this study is to analyze the effect of mechanical properties of above-knee protheses on amputee gait. In this paper, the mechanical properties of knee joints of above-knee prostheses and the gait data for above-knee amputees with different prosthetic knee joints are reported. The angle and the moment of seven knee joints of above-knee protheses in different angular velocities were measured by a muscular training system (Kawasaki Jyuko Ltd.). The angular velocities were changed from 20 deg/sec to 220 deg/sec. Gaits of four normal subjects and three above-knee amputees at different walking speeds were measured by three-dimensional motion measuring system (Hamamatsu Hotonikus Ltd.) and force plates (Kyowa Dengyo Ltd.). The angular displacement, joint moment, and power of the hip and knee joints were calculated by a link segment model. The walking speeds were in cadence 80, 100, and 120 step/min. Prosthetic knees used in this study were Mauch S-N-S Low Resistance (hydraulic), HOSMER Dupaco (hydraulic), and OTTO BOCK 3R-15 (constant friction). As a result, the mechanical properties of knee joints differed. For the gait data, the angular displacement and the moment of the hip joint of the above-knee amputees showed jerky movements when the constant friction prosthetic knee was used. The constant friction prosthetic knee could not achieve smooth hip movement in the swing phase because of insufficient knee function. On the other hand, the hydraulic prosthetic knee could achive smooth hip movement in the swing phase. It was almost the same movement as in normal subjects.

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The examination of tooth mobility is very important to estimate the condition of the periodontium in prosthodontics, orthodontics, periodontics, etc. A manual examination of tooth mobility, which is done by moving the tooth with fingers or dental hand instruments, is carried out regularly in dental clinics. In conjunction with the radiograph, the mobility examination is useful in determining whether there is sufficient alveolar attachment to warrant endodontic treatment or not. The readings, M0-M3, of trained dentists may correspond to the degree of tooth movement, but their interpretation requires skill and experience. We have previously reported on the automatic diagnosis system of tooth mobility for objectively determining the tooth mobility in clinical practice, by applying a small random vibration (30-1000Hz) to the labial crown of a tooth. The system is composed of a measuring probe, with a vibrator and an impedance-head, and a data analysis unit using a personal computer. The biomechanical mobility spectrum of the periodontium is obtained, and the viscoelasticity of the periodontal ligament correlates closely with the tooth mobility. The system is on a fairly large scale, because of the use of a personal computer. In a previous study, the authors developed a new tooth movement transducer. The transducer utilizes bi-morph piezoelectric ceramics, and is therefore small, light, and convenient. Measuring frequency is the resonance frequency of the transducer, and the measurement is made at a constant preload. Hence, the transducer is highly accurate and reliable. The authors applied this transducer to a sensor system for measuring tooth mobility. The tooth movement transducer is located on the Tooth Mobility (T-M) tester. In this tester, a sinusoidal vibration is applied to the tooth crown, and acceleration response is detected. The measured value is proposed as the index of the tooth mobility, Mobility Index (MI) score, corresponding to the tooth movement. The tester is characterized by portability and rapid measurement. The clinical practicality of the tester is examined by using artificial tooth models, and the tooth mobility of maxillary and mandibular teeth is measured.

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An automatic segmentation method of locomotor organs and soft tissues, bones, muscular tissues and joint disc from medical images has been required in the field of plastic surgery and biomechanics. For this purpose, a region-growing method was used generally. In the general region-growing method, a core grows to add a homogeneous pixel judged from its features (edge, intensity and so on) based on image information. However, the bones and tissues in the medical images of the joint are not always extracted by a region-growing method based on only image information. A geometric model of the tissues should not be used for this purpose, because a number of locomotor organs exist and we cannot prepare models for all the tissues. Thus, we improve the conventional region-growing method by using not only image information but also anatomical features of the tissues. The bones and other tissues are extracted by the present method without geometric models. The shape of the core is determined from the core of the previous image because of spatial continuity of the tissues. Next, the core position is estimated roughly in the limitation area as follows: A template pattern of the core was obtained from the previous image, and the core position in the present image was determined by template-matching. The template-matching was performed in the limitation area that was determined by structural features of the bone and the tissues. As a result, estimated core position corresponds to the best matching position of the template pattern obtained from the previous image. When there is continuity of the tissue shape between the cross-section images, the pixel adjoining the core is judged to either add to the core or not by using following anatomical features: location of the tissue (range from the core), complexity of the shape (perimeter/area) and size (area). These anatomical features are described in fuzzy rules and the judgment was performed by the anatomical features and image information using fuzzy reasoning method. In the ideal case, manual digitization of the tissues was required only at the first of the cross-section images. In reality, the region segmented by the present method was not always suitable. If the segmented region was unsuitable, redigitization was required. Using the present method, intereosseous membrane was segmented from coronal MR images of forearms, and the movements of the articular disc were obtained from a temporal series of sagittal MR images. The segmented shapes by this method agreed with the shape segmented by a medical doctor. Three-dimensional shapes of the intereosseous membrane in supination and pronation were obtained from the segmented region. As a result, it was found that the present method would be a new method of measuring of joint detail motion for biomechanics.

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