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1.
Koyama H Muraki Y Ae M 《Sports biomechanics / International Society of Biomechanics in Sports》2006,5(2):139-153
We investigated the immediate effects of the combined use of inclined and raised flat boards on the take-off motion of the long jump. Eight male long jumpers were videotaped with two high-speed video cameras (250 Hz) set perpendicular to the runway. The athletes jumped with three modified take-off boards: upward-inclined boards of two different inclinations (2.5 and 5.0 degrees), and a raised flat board (50 mm high). The jumpers performed pre- and post-jumps using their own techniques before and after use of the boards to test their effects. The post- jump revealed significantly less reduction in the horizontal velocity during the take-off than the pre-jump, and the effectiveness of converting the velocity from horizontal to vertical increased significantly in the post-jump. The post-jump demonstrated significantly less knee flexion of the take-off leg during take-off. The reduced knee flexion and slower extension velocity of the take-off leg in the second phase of the post-jump contributed to increasing the knee extension torque in the second phase and resulted in the increases in vertical ground reaction force and vertical velocity. These results suggest that the combined use of the inclined and raised flat boards induced immediate effective changes in the kinematics and kinetics of the take-off motion and represent appropriate training tools for take-off techniques of the long jump. 相似文献
2.
A non-rotational (NR) shot is now a well-known scoring move in soccer. To execute the NR shot, it is necessary to deprive the ball of any rotational forces during the impact phase. To execute the NR shot, it is natural that the force vector acting from the foot would pass through the ball’s center of gravity; however, the coordinated motion of the lower limb joint’s angular displacement and the pelvis is still unclear. The aim of this study is to estimate the coordinated leg and pelvis motion during the NR shot as compared to that during instep kicking. Four right-leg dominant college league players were asked to perform a NR shot and an instep kick a total of 10 times each. Hip, knee, and ankle joint angular displacements in the sagittal plane and pelvis yaw and roll rotational motions during both types of kicks were calculated with 14 IR reflective markers using a 3D real-time motion analysis system with a 250-Hz sampling. The Euclidean distances of the joint space of the NR shot and the instep kick were also calculated to detect similarities in the coordinated motion of the lower limb. The results showed that the lower limb joint motions in the sagittal plane were not different; however, the pelvis roll and yaw motions were apparently different, and these phenomena could simulate a pendulum motion with changes in both the vertical and horizontal displacements. These results suggest that the coordinated motion of the lower limb joint’s angular displacement shows high similarity between the NR shot and the instep kick, and the pelvis roll and yaw synchronized orientation is essential for achieving the NR shot. 相似文献
3.
Toshiaki Miyamoto Hiroyuki Kamada Akira Tamaki Toshio Moritani 《European Journal of Sport Science》2016,16(8):1104-1110
The aim of this study was to investigate the effect of low-intensity exercise training using belt electrode skeletal muscle electrical stimulation on muscle strength and cardiorespiratory fitness in healthy subjects. Nineteen healthy subjects were allocated into control or intervention groups; in both groups the participants kept regular physical activity while the intervention group underwent 30 min B-SES training at 3–4 METs for four weeks. Knee extensor muscle strength and cardiorespiratory endurance during incremental exercise test were measured at baseline and after four weeks for all participants. The relative change of knee extensor muscle strength in the intervention group was significantly higher than control group (p?p?相似文献
4.
汉语“站立”义词的现状与历史 总被引：7，自引：0，他引：7
表示站立意义的词属于人类语言的基本词。本文描述汉语站立义词的现实分布和历时演变,并尝试对两者的关系作出解释。现代方言中表站立义的主导词有3个:站、立、徛。它们的分布特点是:站分布最广,大多数北方方言说站,此外还散见于非官话区的部分方言点;徛密集分布于东南部的吴语、徽语、赣语、湘语、客家话、广西平话、粤语、闽语地区;立则呈零散分布,散落在官话、晋语、吴语、赣语、湘语、湖南乡话和广西平话各区。这3个词在汉语史上的情况大致是:立从有文字记载的上古早期起一直是影响最大的通语词,直到明代以后才在大部分北方地区被站替换;徛(倚)用作站立义始见于战国,历史上可能作为一个方言词一直存在于南部广大地区;站始见于唐代,明代以后在广大的官话区逐渐取代立成为新的通语词。站很可能是所谓的长江型词,即兴起于江淮流域而后往北扩散。 相似文献
5.
Takahito Iga Hiroyuki Nunome Shinya Sano Nahoko Sato Yasuo Ikegami 《Sports biomechanics / International Society of Biomechanics in Sports》2018,17(4):477-493
To assess ball impact force during soccer kicking is important to quantify from both performance and chronic injury prevention perspectives. We aimed to verify the appropriateness of previous models used to estimate ball impact force and to propose an improved model to better capture the time history of ball impact force. A soccer ball was fired directly onto a force platform (10 kHz) at five realistic kicking ball velocities and ball behaviour was captured by a high-speed camera (5,000 Hz). The time history of ball impact force was estimated using three existing models and two new models. A new mathematical model that took into account a rapid change in ball surface area and heterogeneous ball deformation showed a distinctive advantage to estimate the peak forces and its occurrence times and to reproduce time history of ball impact forces more precisely, thereby reinforcing the possible mechanics of ‘footballer’s ankle’. Ball impact time was also systematically shortened when ball velocity increases in contrast to practical understanding for producing faster ball velocity, however, the aspect of ball contact time must be considered carefully from practical point of view. 相似文献
6.
Hiroyuki Nunome Yasuo IkegamI Rumi Kozakai Tommy Apriantono Shinya Sano 《Journal of sports sciences》2013,31(5):529-541
Abstract Detailed time-series of the resultant joint moments and segmental interactions during soccer instep kicking were compared between the preferred and non-preferred kicking leg. The kicking motions of both legs were captured for five highly skilled players using a three-dimensional cinematographic technique at 200 Hz. The resultant joint moment (muscle moment) and moment due to segmental interactions (interaction moment) were computed using a two-link kinetic chain model composed of the thigh and lower leg (including shank and foot). The mechanical functioning of the muscle and interaction moments during kicking were clearly illustrated. Significantly greater ball velocity (32.1 vs. 27.1 m · s?1), shank angular velocity (39.4 vs. 31.8 rad · s?1) and final foot velocity (22.7 vs. 19.6 m · s?1) were observed for the preferred leg. The preferred leg showed a significantly greater knee muscle moment (129.9 N · m) than the non-preferred leg (93.5 N · m), while no substantial differences were found for the interaction moment between the two legs (79.3 vs. 55.7 N · m). These results indicate that the highly skilled soccer players achieved a well-coordinated inter-segmental motion for both the preferred and non-preferred leg. The faster leg swing observed for the preferred leg was most likely the result of the larger muscle moment. 相似文献
7.
Eating, drinking, locomotion, and rearing activities of rats, maintained under a 12:12-h dark:light cycle, were measured continuously over 24 h a day for 40 days in the KGbox-24. For 20 days, beginning on Day 11, the shocks were given through the grid floor of the box 1 h after the beginning of the dark phase (at 2100 h). The daily food and water intake decreased, and there was no further gain in body weight after the introduction of shocks. The 2100-h shocks had some associative effects: (1) Suppression of ingestion developed during the period of 2000–2100 h; (2) acceleration of general activity developed during the period of 2000–2012 h; (3) anticipatory suppression of eating developed toward the end of the light phase. The 2100-h shocks also had suppressive aftereffects upon eating and drinking, especially during the early stage of the 20-day shock phase. Compensatory drinking was observed during the light phase, but no such effect was found for eating. Some findings which are not usually obtained in short-session experiments remain to be explained. References to two timing systems are made. 相似文献
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A new sensor for detecting ski bending and torsional deflection during an actual ski turn on the snow has been developed.
It consisted of bending and torsion sensors connected by light rigid beams. This structure was fixed to the upper surface
of a ski and passed through a tunnel in the central binding plate. The bending and torsion sensors were strain cells, designed
to reject strain orthogonal to the desired measurement direction. The calibration factor for each sensor was determined in
a jig, then the calibration of the overall sensor assembly was checked by static bending experiments and a free vibration
test. A data logger recorded the strain signals synchronously with other data such as the components of the earth’s magnetic
field measured by a sensor on the ski. The data set allowed reconstruction in software of the instantaneous shape, direction
and edge angle of the ski. The purpose of this paper is mainly to introduce the equipment used and methods developed. Tests
of the sensor performance are described. Results from a ski run on snow are presented to show how the various types of data
can be combined. A skilled ski athlete performed long turns with the ski at about 60 km/h on a groomed snow surface at Shiga
Kogen in Japan. The experiment on snow showed that the deformation of the ski was predominantly bending; torsional deflection,
although measurable, had only a small effect on the shape of the running edge. The ski edge adopted a symmetrical circular
bent shape with an unexpectedly small radius when on the outside, but was unconstrained, lightly loaded and nearly straight
when on the inside. 相似文献
10.
We have studied the contraction and extension of Vorticella convallaria and its mechanical properties with a microfluidic loading system. Cells of V. convallaria were injected to a microfluidic channel (500 μm in width and 100 μm in height) and loaded by flow up to ∼350 mm s−1. The flow produced a drag force on the order of nanonewton on a typical vorticellid cell body. We gradually increased the loading force on the same V. convallaria specimen and examined its mechanical property and stalk motion of V. convallaria. With greater drag forces, the contraction distance linearly decreased; the contracted length was close to around 90% of the stretched length. We estimated the drag force on Vorticella in the channel by calculating the force on a sphere in a linear shear flow. 相似文献