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Walter Quispe Marquez Masanao Masumura Michiyoshi Ae 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(2):154-166
The purpose of this study was to assess the effects of jumping distance on the landing mechanics after a volleyball spike, to help in injury prevention and training for safer landing. Ground reaction forces and three-dimensional kinematic data were collected from six male university right-handed volleyball players under “Normal” and “Long” jumping distance conditions of landing after a spike. The results revealed that the landings under the Long jumping distance condition produced significantly greater centre of gravity velocities and larger mean loading rates. Although data were collected for bilateral landings with the two feet contacting the force platform at the same time, landing motion was asymmetric and the left leg was considered to play a more critical role in the absorption of the landing impact. The trunk and hip positions at the initial contact with the floor and the range of motions of the knee and ankle were key kinematic parameters for reducing the vertical peak ground reaction forces and extending the time from the initial contact to the occurrence of this peak force, which consequently reduced the mean loading rate upon landing. 相似文献
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Kazumichi Ae Sekiya Koike Norihisa Fujii Michiyoshi Ae Takashi Kawamura 《Sports biomechanics / International Society of Biomechanics in Sports》2017,16(3):283-296
The purpose of this study was to investigate effects of the ground reaction forces on the rotation of the body as a whole and on the joint torques of the lower limbs associated with trunk and pelvic rotation in baseball tee batting. A total of 22 male collegiate baseball players participated in this study. Three-dimensional coordinate data were acquired by a motion capture system (250 Hz), and ground reaction forces of both legs were measured with three force platforms (1,000 Hz). Kinetic data were used to calculate the moment about the vertical axis through the body’s centre of mass resulting from ground reaction forces, as well as to calculate the torque and mechanical work in the lower limb joints. The lateral/medial ground reaction force generated by both legs resulted in the large whole body moment about its vertical axis. The joint torques of flexion/extension of both hips, adduction of the stride hip and extension of the stride knee produced significantly larger mechanical work than did the other joint torques. To obtain high bat-head speed, the batter should push both legs in the lateral/medial direction by utilising both hips and stride knee torques so as to increase the whole body rotation. 相似文献
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Hoga K Ae M Enomoto Y Yokozawa T Fujii N 《Sports biomechanics / International Society of Biomechanics in Sports》2006,5(2):167-182
This study analyzed the joint torque and the mechanical energy flow in the support legs of skilled male race walkers. Twelve race walkers were videotaped using a high-speed camera at a frame rate of 250 Hz set perpendicular to the sagittal plane of motion; their ground reaction forces were measured with two force platforms. A two-dimensional, 14-segment, linked model was used to calculate the kinetics of the support leg joints. In the initial part of the support phase, the mechanical energy flowed into the thigh and shank by the torque of the large hip extensors and knee flexors. In the middle part, the mechanical energy generated by the torque of the large plantar flexors flowed to the foot and from the foot to the shank by the ankle joint force. The mechanical energy flow by the forward joint force of the support hip was significantly related to the walking speed in the final part of the support phase. Our findings suggest that race walkers in the final part of the support phase should exert the torque of the knee extensors and hip flexors to transfer the mechanical energy more effectively to the support thigh and shank. 相似文献
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Muraki Y Ae M Yokozawa T Koyama H 《Sports biomechanics / International Society of Biomechanics in Sports》2005,4(1):1-15
The aim of this study was to establish the functions of the support leg in the long jump take-off with a three-element mechanical model spring, damper, and actuator The take-off motions of eleven male long jumpers, with personal bests from 6.45 to 7.99 m, were videotaped at 250 Hz and ground reaction forces were simultaneously recorded at 1 kHz. A two-dimensional 14-segment linked model was used to collect basic kinematic parameters. The spring, damper and actuator forces were determined from the displacement and velocity of the centre of mass and from ground reaction forces. Large spring and damper forces were exerted, and absorbed the impact force immediately after the touch-down. The spring force was also exerted from 25 to 75% of the take-off phase. The actuator force was dominant in the latter two-thirds of the take-off phase. Statistically significant correlations were found between the spring force impulse and the knee flexion during the take-off phase (r = 0.699, p < 0.05), and between the knee flexion and the angular velocity of the thigh at the touch-down (r = 0.726, p < 0.05). These results indicated that the jumper should retain less flexion of the take-off leg knee to increase the spring force, after a fast extension of the hip, and use a more extended knee at the touch-down to prevent excessive knee flexion. 相似文献
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Yasuto Kobayashi Michiyoshi Ae Akiyo Miyazaki Norihisa Fujii Akira Iiboshi Hideki Nakatani 《Sports biomechanics / International Society of Biomechanics in Sports》2016,15(3):314-328
The purpose of this study was to investigate joint kinetics of the throwing arms and role of trunk motion in skilled elementary school boys during an overarm distance throw. Throwing motions of 42 boys from second, fourth, and sixth grade were videotaped with three high-speed cameras operating at 300 fps. Seven skilled boys from each grade were selected on the basis of throwing distance for three-dimensional kinetic analysis. Joint forces, torques, and torque powers of the throwing arm joints were calculated from reconstructed three-dimensional coordinate data smoothed at cut-off frequencies of 10.5–15 Hz and by the inverse dynamics method. Throwing distance and ball velocity significantly increased with school grade. The angular velocity of elbow extension before ball release increased with school grade, although no significant increase between the grades was observed in peak extension torque of elbow joint. The joint torque power of shoulder internal/external rotation tended to increase with school grade. When teaching the overarm throw, elementary school teachers should observe large backward twisting of trunk during the striding phase and should keep in mind that young children, such as second graders (age 8 years), will be unable to effectively utilise shoulder external/internal rotation during the throwing phase. 相似文献
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Digital government infrastructures provide generic functionalities that are used by large numbers of users. Typically, they have no central authority, are governed by networks and contain both emerging and purposefully designed parts. Their use varies over time, and a large number of individuals use them for different purposes. The basic digital government infrastructure has evolved over time and the development towards the next generation of digital government infrastructure (NGI) is under development. In this introduction, we discuss aspects of infrastructure development and this special issue contains papers contributing to the development of the NGI in various fields including customs, crisis management, legislation and regulation, providing a number of possible functions and services that may become part of the NGI. We argue that policy-makers should view the NGI from a complex-adaptive systems (CAS) view and that the next generation of infrastructures will provide not only technological services, including connectivity and security, but also shared information and knowledge in various fields, thus making it easier to participate, translate legislation and manage collaboration between public and private parties and in this way advancing digital government. 相似文献
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