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Benjamin K. Williams Ross H. Sanders Joong Hyun Ryu Philip Graham-Smith Peter J. Sinclair 《Journal of sports sciences》2020,38(10):1115-1123
ABSTRACT To maintain the accuracy of squash shots under varying conditions, such as the oncoming ball’s velocity and trajectory, players must adjust their technique. Although differences in technique between skilled and less-skilled players have been studied, it is not yet understood how players vary their technique in a functional manner to maintain accuracy under varying conditions. This study compared 3-dimensional joint and racket kinematics and their variability between accurate and inaccurate squash forehand drives of 9 highly skilled and 9 less-skilled male athletes. During inaccurate shots, less-skilled players hit the ball with a more open racket, demonstrating a difference in this task-relevant parameter. No joint kinematic differences were found for accuracy for either group. Coordinated joint rotations at the elbow and wrist both displayed a “zeroing-in” effect, whereby movement variability was reduced from the initiation of propulsive joint rotation to a higher consistency at ball-impact; potentially highlighting the “functionality” of the variability prior to the impact that enabled consistent task-relevant parameters (racket orientation and velocity) under varying conditions. Further, highly skilled players demonstrated greater consistency of task-relevant parameters at impact than less-skilled players. These findings highlight the superior ability of highly skilled players to adjust their technique to achieve consistent task-relevant parameters and a successful shot. 相似文献
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Benjamin Kane Williams Ross H. Sanders Joong Hyun Ryu Pitre C. Bourdon Philip Graham-Smith Peter J. Sinclair 《Sports biomechanics / International Society of Biomechanics in Sports》2019,18(2):202-214
Magnetic-inertial measurement units (MIMUs) are becoming more prevalent in sports biomechanics and may be a viable tool to evaluate kinematic parameters. This study examined the accuracy of a MIMU to estimate orientation angles under static conditions and dynamically from a squash racket during a forehand drive shot. A MIMU was mounted onto a goniometer and moved through 0–90°, with static data collected at 10° increments during 10 repetitions of all three axes. Typical error analyses showed the MIMU to be very reliable (TE ≤ 0.03°). MIMU accuracy was determined via intraclass correlation coefficients (ICC) (r > 0.999, p < 0.001). An ordinary least products regression showed no proportional bias and minimal fixed bias for all axes. Dynamic accuracy was assessed by comparing MIMU and optical motion capture data of squash racket swing kinematics. A MIMU was fixed onto a racket and 10 participants each hit 10 forehand shots. Mean orientation angle error at ball impact was <0.50° and ICC showed very high correlations (r ≥ 0.988, p < 0.001) for all orientations. Swing phase root mean squared errors were ≤2.20°. These results indicate that a MIMU could be used to accurately and reliably estimate selected racket swing kinematics. 相似文献
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This study aimed to identify the continuous ground reaction force (GRF) features which contribute to higher levels of block phase performance. Twenty-three sprint-trained athletes completed starts from their preferred settings during which GRFs were recorded separately under each block. Continuous features of the magnitude and direction of the resultant GRF signals which explained 90% of the variation between the sprinters were identified. Each sprinter’s coefficient score for these continuous features was then input to a linear regression model to predict block phase performance (normalised external power). Four significant (p < 0.05) predictor features associated with GRF magnitude were identified; there were none associated with GRF direction. A feature associated with greater rear block GRF magnitudes from the onset of the push was the most important predictor (β = 1.185), followed by greater front block GRF magnitudes for the final three-quarters of the push (β = 0.791). Features which included a later rear block exit (β = 0.254) and greater front leg GRF magnitudes during the mid-push phase (β = 0.224) were also significant predictors. Sprint practitioners are encouraged, where possible, to consider the continuous magnitude of the GRFs produced throughout the block phase in addition to selected discrete values. 相似文献
4.
Minjung Ryu 《International Journal of Science Education》2019,41(10):1303-1323
Bilingual and multilingual speakers mix two or more languages for communication, gaining information and sense-making in varieties of contexts. How do bilinguals mix languages and what does the mixing afford for their learning and participation? This study examines these questions, focusing on Korean-English bilingual youths in a community-based after-school science programme in the United States. A close analysis of videorecordings of the programme sessions demonstrates the ways in which bilinguals negotiate their participant positions and negotiate meanings in their study of science topics. The findings reveal that bilinguals utilise their Korean proficiency to craft diverse ways of participation and that linguistic and scientific sense-making co-occur and support each other. Based on these findings, I offer implications as to how science teachers should perceive students’ mixing of multiple languages and how they can support bilinguals’ learning of science content and English. Additionally, I suggest a future research direction that can help teachers to prepare for linguistically diverse science-learning and -teaching contexts. 相似文献
5.
Jiyoung Ryu 《Early Childhood Education Journal》2004,32(3):165-171
This research article describes the English acquisition of three, young, high-achieving, Korean, bilingual students, their academic development and their social/psychological adjustment in school. All observations and interviews were conducted in the natural classroom setting. The Korean children underwent different school experiences, partially contingent upon their English proficiency, but they generally demonstrated rapid English acquisition and healthy adjustment to school. The study findings suggest that teachers and parents play an important role in supporting their bilingual children's adjustments to new environments while preserving fundamental aspects of their original culture. Recommendations for both mainstream andbilingual teachers are suggested to further an understanding of Korean children, as English language learners and enable these children to become bilingual in Korean and English. 相似文献
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Ji Young Choi Diane Horm Shinyoung Jeon Dahyung Ryu 《Early education and development》2019,30(3):337-356
Research Findings: This study examined whether children’s outcomes at age 3 were predicted by their experiences in Early Head Start (EHS), focusing on 2 key features of infant and toddler care: (a) stability of care and (b) teacher–child interactions. This study further explored potential interaction effects between stability of care and teacher–child interactions in predicting child outcomes. Three main results were found from secondary analyses of the recently released EHS longitudinal data set the EHS Family and Child Experiences Study (Vogel & Boller, 2009–2012). First, children who had stability of care (no teacher change) were rated as having fewer behavior problems and higher social competence. Second, children were rated as demonstrating better orientation/engagement and emotional regulation when they were in EHS classrooms observed to have higher emotional and behavioral support. Third, teacher–child interactions that are emotionally and behaviorally supportive may mitigate the potential drawbacks of experiencing instability of care on early social-emotional development. Study implications are discussed. Practice or Policy: Both stability and quality teacher–child interactions are important in center-based infant and toddler care, and ensuring quality teacher–child interactions is particularly important for children who experience teacher changes during their infant and toddler years. 相似文献
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This paper investigates a stability problem for linear systems with time-varying delays. By constructing suitable augmented Lyapunov–Krasovskii functionals, improved stability criteria under various conditions of time-varying delays are derived within the framework of linear matrix inequalities (LMIs). Moreover, to reduce the computational burden caused by the non-convex term including h2(t), how to deal with it is applied by estimating it to the convex term including h(t). Finally, three illustrative examples are given to show the effectiveness of the proposed criteria. 相似文献
9.
Donghyun Ryu Seonjin Kim Bruce Abernethy David L. Mann 《Research quarterly for exercise and sport》2013,84(2):252-262
Purpose: The ability to anticipate the actions of opponents can be enhanced through perceptual-skill training, though there is doubt regarding the most effective form of doing so. We sought to evaluate whether perceptual-skill learning would be enhanced when supplemented with guiding visual information. Method: Twenty-eight participants without soccer-playing experience were assigned to a guided perceptual-training group (n = 9), an unguided perceptual-training group (n = 10), or a control group (n = 9). The guided perceptual-training group received half of their trials with color cueing that highlighted either the key kinematic changes in the kicker's action or the known visual search strategy of expert goalkeepers. The unguided perceptual-training group undertook an equal number of trials of practice, but all trials were without guidance. The control group undertook no training intervention. All participants completed an anticipation test immediately before and after the 7-day training intervention, as well as a 24-hr retention test. Results: The guided perceptual-training group significantly improved their response accuracy for anticipating the direction of soccer penalty kicks from preintervention to postintervention, whereas no change in performance was evident at posttest for either the unguided perceptual-training group or the control group. The superior performance of the guided perceptual-training group was preserved in the retention test and was confirmed when relative changes in response time were controlled using a covariate analysis. Conclusions: Perceptual training supplemented with guiding information provides a level of improvement in perceptual anticipatory skill that is not seen without guidance. 相似文献
10.
Factors Affecting Student Choice of Career in Science and Engineering: parallel studies in Australia,Canada, China,England, Japan and Portugal 总被引：1，自引：1，他引：0
Brian E. Woolnough Yuying Guo Maria Salete Leite Maria Jose de Almeida Tae Ryu Zhen Wang 《Research in Science & Technological Education》2013,31(1):105-121
This paper describes parallel studies carried out in six countries which investigated the factors which influence school students towards careers and higher educational studies in the physical sciences or technology. The studies consisted of a common questionnaire survey, supplemented by student interviews. It reveals differences between scientists and non scientists in regard to their preferred learning styles, to the broad factors which were influential in their career choice and to their self perception against different personality types. Many factors are common across a wide range of countries. Implications of these findings for schools, higher education and government are discussed. 相似文献