International Journal of Sport and Health Science
Online ISSN : 1880-4012
Print ISSN : 1348-1509
ISSN-L : 1348-1509
Volume 3 , Issue Special_Issue_2005
Showing 1-20 articles out of 20 articles from the selected issue
Prefatory Note
Reviews
  • Keitaro Kubo
    Type: Review
    Subject area: Biomechanics
    2005 Volume 3 Issue Special_Issue_2005 Pages 143-151
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    The present study was conducted to evaluate the elastic properties of human tendon structures and their influences on human movements, and to investigate the effects of resistance training on tendon properties. During isometric contraction, the elongations of tendon structures in knee extensors and plantar flexors were measured by means of real-time ultrasonography. The resulting tendon force and elongation relationship was non-linear in form, as previously reported on animal and human cadaver tendons in vitro. The estimated Young's modulus, i.e., the slope of the stress - strain curve, tended to be lower than the previously reported values. In human movements, the elastic properties of tendon structures had a favorable effects on stretch-shortening cycle exercises, possibly because of improved storage and release of elastic energy. Furthermore, the adaptation of the tendon structures to physical training varies with the combinations of intensity, contraction time during exercise as previously observed in the animal experiments. Furthermore, the elastic properties of human tendon structures could be new indices of physical resources in vivo.
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  • Senshi Fukashiro, Dean C. Hay, Shinsuke Yoshioka, Akinori Nagano
    Type: Review
    Subject area: Biomechanics
    2005 Volume 3 Issue Special_Issue_2005 Pages 152-160
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    The purpose of this paper was to review the research findings regarding the biomechanical behavior of the muscle-tendon complex (MTC) during dynamic human movements, especially those obtained using computer simulation. Specific studies conducted by the authors using the free vibration technique and MTC modeling have been discussed in detail. For determining individual viscoelastic characteristics of the human triceps surae MTC groups, a race difference between Black and White college athletes was investigated using the free vibration technique. It was found that the muscle stiffness was greater among Black athletes. Through computer simulation using a Hill-type MTC model, the benefit of making a countermovement was investigated in relation to the length ratio between the contractile element (CE) and the series elastic element (SEE) and the compliance of the MTC. The integral roles of the SEE were simulated in a cyclic human heel-raise exercise. It was revealed that it is beneficial to make a countermovement for explosive activities like vertical jumping, and the benefit of making a countermovement increases as the compliance of the MTC increases. Also, using a MTC model, the effects of moment arm length on kinetic outputs of the musculoskeletal system were evaluated. It was found that longer moment arm resulted in smaller joint moment development, smaller joint power output and smaller joint work output in the larger plantarflexion angular velocity region. It can be said that computer simulation is a powerful tool for determining and evaluating MTC behavior during dynamic human movements.
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  • Hiroaki Kanehisa
    Type: Review
    Subject area: Physiology
    2005 Volume 3 Issue Special_Issue_2005 Pages 161-170
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    This paper summarized previous findings on the morphological responses of human skeletal muscles in decreased mechanical loading conditions, i.e., in bed rest, limb immobilization and space flight, and to discuss how intensity and duration of muscle contractions is needed for preventing muscle atrophy in these conditions. The anatomical cross-sectional areas or volumes of lower limb muscles in a given unloading condition linearly decrease with increasing the time of unloading if the duration is less than about 60 days. Within this duration, space flight induces a greater atrophic change in the lower limb muscles as compared to bed rest and limb immobilization. In addition, the difference in the type of decreased mechanical loading produces different atrophic changes between muscles and between the positions of a muscle group. Resistance exercises with a load for force development at 70%∼of maximum voluntary contraction or one repetition maximum is effective as a countermeasure to muscle atrophy during exposure to unloading condition. On the other hand, there is evidence suggesting that even if a resistive exercise cannot produce hypertrophy in ambulatory condition, it will be an effective measure for preventing muscle atrophy during unloading condition. With regard to the minimal effective training volume as countermeasure, further investigation is needed.
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  • Atsuko Kagaya, Yoshiho Muraoka
    Type: Review
    Subject area: Physiology
    2005 Volume 3 Issue Special_Issue_2005 Pages 171-180
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    Muscle contraction mechanically changes vessel geometry and consequently muscle circulation. Lengthening of muscle fiber straightens capillary tortuosity and further increase in muscle fiber length reduces blood flow by extending the capillary while reducing its diameter. The direction of capillary to the fiber long axis will modify the extent of capillary lumen diameter change due to lengthening muscle fiber. During passive stretching in human subjects, the relationship between changes in blood volume (determined by near-infrared spectroscopy: NIRS) and fascicle length differed among the three heads of triceps surae muscles with different fascicle length and pennation angle. Muscle thickness, muscle curvature, and muscle fascicle angle are potential determinants of intramuscular pressure during muscle contraction. Muscle circulation is impeded more in short bulging muscles with great curvature of fibers than in long slender muscles with less curvature. The different response of circulatory parameters across the synergist muscles in the calf and heterogeneity of muscle circulation in the same muscle were observed, partly due to the difference in the pennation angle of the muscle fascicle. The muscle architecture will influence venous outflow by changing the muscle pumping action. This is possibly an indirect way of modifying vasodilation due to difference in muscle architecture.
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  • Motoki Kouzaki
    Type: Review
    Subject area: Physiology
    2005 Volume 3 Issue Special_Issue_2005 Pages 181-193
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    In examining the roles of synergistic muscles in human activities, it is impossible to consider these muscles as a single functional unit. It is reasonable to assume that the activities of individual synergists during contractions are different because of the variety of anatomical, biomechanical and physiological features of each muscle. This brief review, therefore, proposes three topics that examine the significant roles of synergistic muscles: 1) task-dependent neural activities are modulated by peripheral afferent activities as well as by the central nervous system; 2) the different roles of mono- and bi-articular muscle activities are essential in controlling human movements; and 3) non-fatigued synergistic muscles compensate for a fatigued muscle via peripheral neural interactions. On the basis of a perspective with an emphasis on synergistic relations, I suggest that the different roles of these muscles, which are neurophysiologically regulated, make it possible to control human activities, and that the concept of the muscle-equivalent model is insufficient because human movements are controlled by both redundant and complex systems.
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  • Hiroshi Akima
    Type: Review
    Subject area: Physiology
    2005 Volume 3 Issue Special_Issue_2005 Pages 194-207
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    Imaging is a powerful strategy for the visualization of anatomical and functional information (levels and patterns of activation, perfusion, circulation, and metabolism etc.) in human skeletal muscle. Recent innovations in scientific technology, several new techniques and methods have been developing that visualize the function of muscle regarding recruitment, perfusion, and/or metabolism in exercise. This review is focused on three novel imaging techniques; magnetic resonance imaging, positron emission tomography, and near infrared spectroscopic imaging. These noninvasive imaging techniques provide us crucial information about human muscle function in exercise. The information includes following the assignments; 1) training effects on muscle function, 2) differences in muscle function and metabolism between trained and untrained individuals, and 3) heterogeneity of activation perfusion and metabolism within a single muscle or muscle group. Recent research studies applying these imaging techniques to human muscles are discussed in detail in this review.
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  • Yasuo Kawakami
    Type: Review
    Subject area: Physiology
    2005 Volume 3 Issue Special_Issue_2005 Pages 208-217
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    The present paper reviews previous studies on changes in muscle architecture in humans as a result of strength training. Muscle architecture here refers to 1) muscle size, 2) pennation angle, and 3) muscle fiber length. Training-induced changes are summarized respectively. A typical outcome of strength training is muscle hypertrophy, which is manifested as an increase in muscle size evaluated by cross-sectional area and muscle volume. However, changes also occur in pennation angles and, possibly, in muscle fiber lengths. Increased pennation angles after training have the detrimental effect of producing a reduced force transmission from muscle fibers to tendon, which might lead to a decrease in specific tension or muscle force per physiological cross-sectional area. Recent in vivo studies on human muscles have revealed that changes in pennation angles resulting from training and contraction are much greater than previously thought.
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Papers
  • Norihide Sugisaki, Hiroaki Kanehisa, Yasuo Kawakami, Tetsuo Fukunaga
    Type: Paper
    Subject area: Biomechanics
    2005 Volume 3 Issue Special_Issue_2005 Pages 235-244
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    This study aimed to investigate the behavior of the aponeurosis and external tendon of the medial gastrocnemius muscle (MG) in dynamic actions. Seven males performed maximal and submaximal concentric (CON) and eccentric (ECC) plantar flexion exercises preceded by an isometric action (Pre-iso) on an isokinetic dynamometer at a pre-set velocity of 5°/s. In addition, the subjects performed static ramp actions with the ankle positioned at dorsi-and plantar flexed positions. During the exercises, the length changes of the aponeurosis and external tendon of MG were determined using ultrasound apparatuses. In CON, the length of external tendon significantly shortened from the level of Pre-iso in all test conditions. However, the change of aponeurosis was significant only in the maximal exercises. In ECC, the external tendon was elongated in all test conditions, while the aponeurosis was not elongated even in the maximal effort. In static action, the lengths of both aponerurosis and external tendon increased with increasing force levels. The present results indicate that the behavior of aponeurosis of MG depends on the type of action and that the aponeurosis of MG plays a simple role of muscle force transmission in eccentric actions, while external tendon functions to store elastic energy.
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  • Toshiaki Oda, Hiroaki Kanehisa, Kentaro Chino, Toshiyuki Kurihara, Tos ...
    Type: Paper
    Subject area: Biomechanics
    2005 Volume 3 Issue Special_Issue_2005 Pages 245-252
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    The present study aimed to determine the differences in the length-force relationship between muscle fiber and muscle tendon complex (MTC) and to relate the shape of the length-force relationship to the architectural changes in MTC (the elongation of tendon structures and pennation angle changes). In six male subjects, tetanic contractions (2s at 50Hz) of the tibialis anterior muscle were induced electrically. At a steady state of tetanic contraction, the muscle fiber length and pennation angle were measured from ultrasonic images, and the muscle fiber force, tendon force, MTC length and elongation of tendon structures were calculated. The measured and normalized length-force relationships were clearly different between muscle fiber and MTC, especially on the length axis. The differences could be attributed to the existence of compliant tendon structures and increment of pennation angles related to elongation of tendon structures, suggesting that compliant tendon structures in human muscles influence the length-dependent force generation in both muscle fiber and MTC.
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  • Senshi Fukashiro, Sadao Kurokawa, Dean C. Hay, Akinori Nagano
    Type: Paper
    Subject area: Biomechanics
    2005 Volume 3 Issue Special_Issue_2005 Pages 253-263
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    The fascicular and tendinous behavior of the human m. gastrocnemius medialis (MG) was measured using ultrasonography between vertical ankle- and drop-jumping in order to better understand how force is developed under dynamic conditions. These jumps employed movement at the ankle joint only, and the MG was defined as the agonist muscle of the jumps. Eight male subjects performed 1: Ankle plantarflexion jumping (AJ) from the standing position without countermovement, and 2: straight legged Drop jumping (DJ) from a height of 0.20 m; both with maximal effort. Length, force and power output of the muscle-tendon complex (MTC), fascicles and tendinous structures were estimated from a video tape recorder (VTR)/force-plate system and ultrasonography. EMG of the triceps surae was simultaneously measured. Vertical displacements of the body center of gravity were 0.16m in AJ and 0.33m in DJ. There was no stretching phase of the fascicles during the take-off phase in both AJ and DJ. Physiological effects such as stretch reflex and potentiation did not appear to be present. Even in AJ, the fascicles of the MG shortened in the earlier phase of take-off compared to the MTC of MG. As a result, the elastic energy was stored (2.2 J) and reutilized (2.1 J: 47% of total MTC work in latter phase) during the push-off phase. In DJ, on the other hand, much elastic energy was stored in the tendinous structures during dorsiflexion (7.6 J) and plantarflexion (5.8 J: 75%) phases. It was quantitatively indicated that there was a large advantage from elastic energy use in DJ compared to AJ. The MG fascicles operated within the optimal phase of the sarcomere force-length relationship in AJ and DJ. Also, the fascicles worked in the relatively low shortening velocity region of the instantaneous force-velocity relationship in AJ and DJ.
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  • Akinobu Wakayama, Akira Shibayama, Daisuke Takeshita, Dean C. Hay, Jun ...
    Type: Paper
    Subject area: Biomechanics
    2005 Volume 3 Issue Special_Issue_2005 Pages 264-271
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    The purpose of this study was to investigate the contribution of the series elastic component (SEC) to muscle-tendon complex (MTC) power during concentric elbow flexion. The subjects were 8 healthy female students. Subjects maximally flexed the elbow joint from 60 to 90 degrees from a relaxed state. A randomized weight load from 1.0kgw to 5.0kgw, in 1.0kgw increments was used. The anatomical parameters of elbow flexor muscles were estimated beforehand. The Hill type model was utilized to discuss the performance of the elbow flexor MTC. The peak MTC power was observed between 83 to 86 deg for all weight loads. The averages of MTC power at 85 deg from 1.0 to 5.0kgw (29 to 49% of maximal force) ranged from 160 to 174W, respectively. The averages of the contractile component (CC) power ranged from 149 to 164W and SEC power values ranged from 9.6 to 11.6W, respectively. An analysis of the data using Hill's equations revealed that the average optimal load to provide maximal MTC power at 85 deg was 42% of maximal force. In this condition, the contribution of SEC on MTC power was 6.2%. In the conditions ranging from 0%<maximal force<100%, the contributions of SEC varied from 4.9 to 7.8%. Therefore, the peak MTC power generation in concentric contraction was not greatly affected by the recoiled elastic energy of SEC.
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  • Senshi Fukashiro, Thor F. Besier, Rod Barrett, Jodie Cochrane, Akinori ...
    Type: Paper
    Subject area: Biomechanics
    2005 Volume 3 Issue Special_Issue_2005 Pages 272-279
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    The purpose of this study was to perform a detailed kinematic, kinetic, and electromyographic comparison of maximal effort horizontal and vertical jumping. It was of particular interest to identify factors responsible for the control of jump direction. Eight male subjects performed maximal horizontal jumps (HJ) and vertical jumps (VJ) from a standing posture with a counter movement. Three-dimensional motion of the trunk, pelvis, and bilateral thigh, shank, and foot segments were recorded together with bilateral ground reaction forces and electromyographic (EMG) activity from seven right leg muscles. Relative to the VJ, the trunk is displaced further forward at the beginning of the HJ, through greater ankle joint dorsiflexion and knee extension. The activity of the biarticular rectus femoris and hamstrings were adapted to jump direction and helped to tune the hip and knee joint torques to the requirements of the task. The primary difference in joint torques between the two jumps was for the knee joint, with the extension moment reduced in the HJ, consistent with differences in activation levels of the biarticular rectus femoris and hamstrings. Activity of the mono-articular knee extensors was adapted to jump direction in terms of timing rather than peak amplitude. Overall results of this study suggest that jump direction is controlled by a combination of trunk orientation at the beginning of the push-off and the relative activation levels of the biarticular rectus femoris and hamstring muscles during the push-off.
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  • Kenji Tauchi, Yasuyuki Kubo, Keigo Ohyama Byun, Kaoru Takamatsu
    Type: Paper
    Subject area: Biomechanics
    2005 Volume 3 Issue Special_Issue_2005 Pages 286-295
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    The purpose of this study was to investigate the effect of the stretch-shortening cycle (SSC) on power output in overhead throwing and on the behavior of shoulder extensor muscles by means of kinematics, kinetics and EMG. Thirteen healthy men performed two kinds of medicine ball throw; concentric throw (CT) without SSC and rebound throw (RT) with SSC. All throws were videotaped using a high-speed camera. Kinematics and kinetics such as joint angle, joint torque and joint torque power of the upper limbs were calculated utilizing the inverse dynamics approach. The EMG activities of trapezius, latissimus dorsi, deltoid, pectoralis major and triceps brachii muscles were recorded using surface electrodes. Mean ball power in RT was significantly higher than that in CT. There was a significant correlation between augmentation of mean ball power and that of mean shoulder joint torque power in RT compared with CT. The EMG activities of pectoralis major and triceps brachii muscles showed nearly no activity during the shoulder flexion phase. These results suggest that although enhancement of power by overhead throwing using upper limb muscles was mainly caused by the enhancement of shoulder joint torque power, the shoulder extensor muscles are not eccentrically contracted but passively stretched during shoulder flexion phase in throwing. This finding contradicts a previously proposed mechanism of power enhancement in SSC.
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  • Emika Kato, Toshiaki Oda, Kentaro Chino, Toshiyuki Kurihara, Toshihiko ...
    Type: Paper
    Subject area: Physiology
    2005 Volume 3 Issue Special_Issue_2005 Pages 218-225
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    Flexibility is often evaluated from the joint range of motion (ROM), but the mechanisms underlying gender differences in joint ROM have not been elucidated. The purpose of this study was to investigate the factors influencing the difference in ankle joint ROM between men and women with respect to the extensibility of muscle-tendon complex. Eighteen men (21-26 yr, 66.4±6.0kg, 173.7±7.4cm mean±SD) and 12 women (19-27yr, 52.9±4.8kg, 163.4±4.3cm) participated in this study. Each subject was seated with the knee extended, and the ankle joint was attached to a foot plate, by which the ankle joint was passively dorsiflexed with torque gradually increasing from zero to a value at which the passive loading to the ankle joint was just tolerable for each subject. During the passive loading, real-time ultrasonogram was taken to track the movement of MTJ (muscle-tendon junction of the gastrocnemius medialis and Achilles tendon) as the elongation of muscle belly (dMus). The change of MTC (muscle-tendon complex) length (dMTC) during the passive dorsiflexion was estimated from changes in ankle joint angle. Tendon elongation (dTen) was calculated by subtracting dMus from dMTC. There was no significant difference in normalized passive torque during passive dorsiflexion between men and women. Women were more flexible, i.e., they demonstrated greater dMTC, which was accompanied by greater dTen at lower torque levels. However, dMus was not different between men and women. It was concluded that gender difference in the joint ROM at the ankle reflects more compliant Achilles tendon in women than in men.
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  • Toshiyuki Kurihara, Toshiaki Oda, Kentaro Chino, Hiroaki Kanehisa, Tet ...
    Type: Paper
    Subject area: Physiology
    2005 Volume 3 Issue Special_Issue_2005 Pages 226-234
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    The fascicle lengths of the human gastrocnemius muscle during isometric plantar flexions were analyzed using a three-dimensional ultrasound system (3D-US). Prior to measurements in vivo, the accuracy and reproducibility of the 3D-US were examined by taking images of a phantom. The horizontal errors were 0.3-1.0%, and the vertical errors were 1.2-1.6%. In addition, the coefficients of variance for the repeated measurements were 3.3% and 1.7% for horizontal and vertical directions, respectively. Second, both at rest and each of five intensities {20, 40, 60, 80, 100% of maximum voluntary contraction (MVC)}, at a fixed ankle joint angle of 90deg, the 3D-US images of gastrocnemius muscles were obtained and used to determine fascicle length. The fascicle length was also measured using two-dimensional ultrasound system (2D-US), and the values obtained by 2D-US were used to make comparisons with those by 3D-US. From rest to MVC, the fascicle length decreased as a function of relative torque levels from 6.0 (± 0.5) cm to 3.1 (± 0.4) cm with 3D-US, and, in a similar manner, from 5.6 (± 0.5) cm to 3.0 (± 0.4) cm with 2D-US. Thus the present study indicated the accuracy and reproducibility of the 3D-US measurements and its usefulness for determining the fascicle lengths of human muscles in three-dimensional space. The fascicle length measurements determined by 3D-US were, however, significantly longer than those of 2D-US.
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  • Yasuhide Yoshitake, Yasuo Kawakami, Hiroaki Kanehisa, Tetsuo Fukunaga
    Type: Paper
    Subject area: Physiology
    2005 Volume 3 Issue Special_Issue_2005 Pages 280-285
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    To examine the origin of mechanomyogram (MMG), we compared the responses of surface MMG with the changes in the fascicle length determined by ultrasonography during electrically induced contractions of human skeletal muscles. The posterior tibial nerve of subjects (n=5) was stimulated with a stimulus pattern in which the frequency rose up from 1Hz to 20Hz linearly. The MMG amplitude decreased with increasing stimulation frequency. Reduction of MMG amplitude was in parallel with the decrease in fluctuation of the changes in fascicle length, and these values had a significant positive correlation (r=0.94, P<0.001). The observed direct relation between MMG and architectural change of muscle indicates that surface MMG is generated by the pressure wave produced by the expansion of a number of muscle fibers during contractions.
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  • Megumi Ohta, Yoshihisa Masuo, Hiroaki Kanehisa, Yasuo Kawakami, Tetsuo ...
    Type: Paper
    Subject area: Physiology
    2005 Volume 3 Issue Special_Issue_2005 Pages 296-303
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    This study aimed to investigate the applicability of the bio-electrical impedance (BI) method for the estimation of tendon elongation due to muscle contraction. We applied the BI method with a cylindrical model to the muscle-tendon complex (MTC). While subjects performed ramp isometric elbow flexion up to 80% of maximal voluntary contraction (MVC), BI was measured using a bio-electrical impedance muscle analyzer. Simultaneously, tendon elongation was also determined directly by ultrasonography. The amount of tendon elongation (ΔLt) and relative BI values (%BI) changed curvilinearly with increasing torque development. There was a significant negative correlation between ΔLt and %BI in each subject (r = 0.924 ∼ 0.994, p<0.01). Thus, the present results indicate the effectiveness of the BI method for the estimation of tendon elongation during muscle contractions in vivo in human.
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Development Paper
  • Akinori Nagano, Shinsuke Yoshioka, Taku Komura, Ryutaro Himeno, Senshi ...
    Type: Development Paper
    Subject area: Biomechanics
    2005 Volume 3 Issue Special_Issue_2005 Pages 311-325
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    A skeletal model of the whole human body was developed, and the script (computer program) of the model is reported in this paper. The model was constructed to be processed with a commercial package AUTOLEV (OnLine Dynamics, Sunnyvale, CA, USA). The model contains sixteen body segments, i.e., head, chest, mid-trunk, lower-trunk, right and left upper arms, right and left lower arms, right and left hands, right and left upper legs, right and left lower legs, and right and left feet. These segments are connected through the neck, chest, stomach, shoulder, elbow, wrist, hip, knee and ankle joints. The total degree of freedom of the model is 35. Passive joint properties of the trunk and lower limb were implemented. As an example, a motion similar to the flight phase of a horizontal jumping motion was simulated, in which the whole body traveled in the air from a given initial posture, with given initial velocities and angular velocities of body segments and joints. Readers can either simply copy the script reported in this paper, or make modifications as needed, to run a simulation. It is hoped that this paper helps encourage many researchers to utilize the technique of computer simulation for further development of individual projects.
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Materials
  • Tetsuro Muraoka, Tadashi Muramatsu, Kazuyuki Kanosue, Tetsuo Fukunaga, ...
    Type: Materials
    Subject area: Biomechanics
    2005 Volume 3 Issue Special_Issue_2005 Pages 304-310
    Published: 2005
    Released: January 23, 2008
    JOURNALS FREE ACCESS
    The purpose of this study was to examine the differences in the geometric and elastic properties of the Achilles tendon between right and left ankles in kendo (japanese fencing) athletes, who engaged in kendo training for years, and matched controls. The subjects were twelve kendo athletes and nine controls (21 and 20 yrs, 65 and 60 kg, and 172 and 171 cm, respectively). While the subjects developed maximum voluntary isometric plantarflexion (MVIP) torque (TQ), the tendon displacement and ankle joint rotation was determined using a B-mode ultrasonograph and a goniometer, respectively. The tendon force (F) was calculated from TQ and the moment arm of the Achilles tendon. The elongation of the Achilles tendon (ΔX) was obtained from the tendon displacement and ankle joint rotation. The cross-sectional area of the Achilles tendon (CSA) was measured using a B-mode ultrasonography. The Achilles tendon stiffness (k) was defined as F divided by ΔX, stress (σ) as F divided by CSA, strain (ε) at MVIP as ΔX divided by the Achilles tendon length at rest (Lr), and Young's modulus (E) as σ divided by ε. The results showed that there were no significant differences in TQ, F, σ, Lr, ΔX, ε, k, and E between right and left ankles for both control and kendo athlete subjects, and between control and kendo athlete subjects. CSA of kendo athletes' right ankles was significantly greater than that of kendo athletes' left ankles (p=0.03). It was suggested that a long-term kendo training did not affect the elastic properties of the Achilles tendon and resulted in smaller Achilles tendon CSA in left ankles.
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