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A Murray TC Aitchison G Ross K Sutherland I Watt D McLean 《Journal of sports sciences》2013,31(9):927-935
The aim of this study was to compare sprint performance over 10 and 20?m when participants ran while towing resistances, weighing between 0 and 30% of body mass. The sample of 33 participants consisted of male rugby and soccer players (age 21.1?±?1.8 years, body mass 83.6?±?13.1?kg, height 1.82?±?0.1?m; mean?±?s). Each participant performed two sets of seven sprints over 20?m using a Latin rectangular design. The times were recorded at 10 and 20?m using electronic speed gates. The sprints of 13 players were video-recorded to allow calculation of stride length and frequency. For both sprints, a quadratic relationship was observed between sprint time and resistance as sprint time increased from 2.94?s to 3.80?s from 0 to 30% resistance. This relationship was statistically significant but considered not to be meaningful for performance because, over the range of resistances used in this study, the quadratic model was never more than 1% (in terms of sprint time) from the linear model. As resistance increased, the stride length shortened, with mean values of 1.63?±?0.13?m at 0% body mass and 1.33?±?0.13?m at 30% of body mass. There was no significant change in stride frequency with increasing resistance. The results show that in general there is an increase in sprint time with an increase in resistance. No particular resistance in the range tested (0?–?30%) can be recommended for practice. 相似文献
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Chun‐Yen Chang Yueh‐Hsia Chang Fang‐Ying Yang 《International Journal of Science Education》2013,35(17):2315-2334
The educational reform movement since the 1990s has led the secondary earth science curriculum in Taiwan into a stage of reshaping. The present study investigated secondary earth science teachers' perceptions on the Goals of Earth Science Education (GESE). The GESE should express the statements of philosophy and purpose toward which educators direct their attention, and provide the visions or broad aims that earth science education is designed to achieve. Based on this rationale, the purpose of this study was to explore teachers' perceptions on the GESE at secondary school level (Grades 7–12) in Taiwan. A national survey of 1,000 earth science teachers was conducted in May 2004, with a response rate of 70.2%. The results revealed that ‘Students acquire basic earth science concepts’ is the most important GESE both in teachers' preferred goal and their actual teaching practice in the secondary earth science education; that there is a major gap between teachers' preferred and actual GESE in terms of ‘Preparing students for the entrance examinations’; and that the differences between teachers' preferred and actual GESE are contingent on the teachers' age, the school size, and the teacher education background of teachers. 相似文献
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Yu-Pin Liang Yi-Liang Kuo Hsiang-Chin Hsu Yen-Ysung Hsia Ya-Wen Hsu 《Journal of sports sciences》2019,37(5):544-552
Sports injuries are common among baseball players and may result in abnormal movement patterns, increased risks of future injury, and unsatisfactory performance. The Functional Movement Screen (FMS?) has been developed to detect abnormal functional movement patterns and can be used for predicting risks of sports injury. However, whether FMS? scores are associated with athletic performance remains unclear. The goal of this study was to determine the association between functional movements and athletic performance in elite baseball players. Core stability, muscular strength and flexibility of the lower extremities, and FMS?, as well as athletic performance in sprinting, agility, and balance tests were assessed in 52 male collegiate Division I baseball players placed into two groups based on FMS? scores. The high-scoring group demonstrated better athletic performance than the low-scoring group, with a shorter duration of the agility test. No group differences were found in core stability, muscular strength, or muscle flexibility, except for rectus femoris flexibility. Thus, the FMS? score is associated with sprinting and agility performance in elite baseball players. These findings indicate that the FMS? may have a role in predicting athletic performance and thereby help determine the goals of training regimens or return-to-play strategies. 相似文献
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A simple iterative technique, which is free of certain shortcomings of the previous methods, is proposed for the approximation of large linear systems by a lower- order model. Here, the measure of the goodness of the approximate model is taken to be the value of the integral-square error between the step responses of the exact and the simplified systems. The proposed technique consists of a two-step iterative scheme. In the first step, the optimum residues are obtained by the minimization of the objective function, while the poles (or eigenvalues) are kept constant. In the second step, the poles are optimized while the residues remain fixed. This procedure is continued cyclically until the objective function is satisfactorily minimized. The necessary and sufficient conditions for existence of an optimum are satisfied in each step. The residues, poles and objective functions converge monotonically. The resulting reduced-order model obtained by this method is stable if the original system is stable. The method can also be applied to systems with repeated poles and to multivariable systems. The results are superior to those obtained previously in the steady-state, the point-by-point transient response, and the value of the integral-square error. Illustrative examples are presented. 相似文献
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Hower J. Hsia 《Educational technology research and development : ETR & D》1969,17(3):272-282
Conclusion It has been assumed that by manipulating redundancy (both SR and BCR), it is possible to make LI Ss perform IP tasks as effectively
as HI Ss. The difference between HI and LI Ss may be eliminated or reduced by improving the performance level of LI Ss. The
simultaneous AV channel presenting identical or high redundancy information (high BCR) would make it possible to raise LI
Ss to a level of performance as high as that of HI Ss.
This study was supported by the Research and Development Center for Learning and Re-Education, University of Wisconsin, pursuant
to contracts with the United States Office of Education (Center N. C-03 /Contract OE, CRP No. 2850). The writer wishes to
thank his major professor, Bruce H. Westley, for his guidance of this study. 相似文献