Key somatic variables in young backstroke swimmers     

Senda Sammoud  Alan Michael Nevill  Yassine Negra  Raja Bouguezzi  Chaabene Helmi  Younés Hachana 《Journal of sports sciences》2019,37(10):1162-1167

The purpose of this study was to estimate the optimal body size, limb-segment length, girth or breadth ratios for 100-m backstroke mean speed performance in young swimmers. Sixty-three young swimmers (boys [n = 30; age: 13.98 ± 0.58 years]; girls [n = 33; age: 13.02 ± 1.20 years]) participated in this study. To identify the optimal body size and body composition components associated with 100-m backstroke speed performance, we adopted a multiplicative allometric log-linear regression model, which was refined using backward elimination. The multiplicative allometric model exploring the association between 100-m backstroke mean speed performance and the different somatic measurements estimated that biological age, sitting height, leg length for the lower-limbs, and two girths (forearm and arm relaxed girth) are the key predictors. Stature and body mass did not contribute to the model, suggesting that the advantage of longer levers was limb-specific rather than a general whole-body advantage. In fact, it is only by adopting multiplicative allometric models that the abovementioned ratios could have been derived. These findings highlighted the importance of considering somatic characteristics of young backstroke swimmers and can help swimming coaches to classify their swimmers and enable them to suggest what might be the swimmers’ most appropriate stroke (talent identification).  相似文献   

挑战、困境与化解:数字环境下我国图书馆合理使用条款及其适用的再探讨     

王果  张立彬 《图书情报工作》2019,63(10):5-11

[目的/意义] 合理使用是维持著作权人个人利益与社会公共利益平衡的重要机制之一，对承担公共文化服务功能的图书馆尤为重要，但实践中图书馆的合理使用条款并未充分发挥利益平衡的作用，有必要对其存在问题及形成原因进行深入分析。[方法/过程] 通过与域外立法相比较，以及司法实践中的案例分析，可看出我国图书馆合理使用的主要问题在于现行法律规定滞后、规则不明晰，导致合理使用适用范围狭窄，还同时受到许可协议、技术措施的挤压。[结果/结论] 为化解图书馆合理使用条款的适用困境，可从增加原则性规定、明确其法律属性为强制性规定、扩大有关条款的适用范围等方面来完善立法。图书馆自身也应加强知识产权管理、提高知识产权素养，严格遵照法律规定以消除侵权隐患。  相似文献   

大学生体质健康测试中运动损伤的调查研究     

朱丽丽  侯毓岭  蒋兰新 《体育科技文献通报》2020,(4):62-63

为了更好地完成《国家学生体质健康标准》的测试工作,本文采用文献资料、逻辑分析、实地考察等方法,对大学生体质健康测试过程中常发生的运动损伤进行了分析,并提出相应的预防措施,为体质健康测试的顺利进行、学生的健康发展、教育主管部门的决策提供了理论依据。  相似文献   

竞技武术套路运动员力量素质的训练措施分析     

安志超  何英 《中华武术(研究)》2020,(4):109-112

在现代竞技武术比赛中,超强的力量素质对创造优异的运动成绩起着重要作用。本文通过文献资料法、逻辑分析法等方法,针对竞技武术套路的运动特点指导和制定科学合理的力量素质训练方法,旨在使竞技武术套路训练走向更加科学化和规范化的道路,以期促进我国武术事业的发展。  相似文献   

Walking and biologic ageing: Evidence based on NHANES telomere data     

Larry A. Tucker 《Journal of sports sciences》2020,38(9):1026-1035

ABSTRACT

The length of telomeres is an objective measure of biologic ageing. This study evaluated the extent minutes of walking per week are associated with leukocyte telomere length (LTL) in a random sample of 5,823 U.S. adults. The investigation was cross-sectional and data were obtained from the National Health and Nutrition Examination Survey (NHANES). LTL was measured by the quantitative polymerase chain reaction method. Walking minutes was calculated from walking frequency and duration measures. Results showed that for each year of chronological age, telomeres were 15.6 base pairs shorter (P < 0.0001). With walking minutes and LTL treated as continuous variables, the relationship was quadratic, not linear (F = 11.2, P = 0.0023). With walking time divided into three categories, adults who performed ≥ 150 minutes of walking per week had longer telomeres than those who did no regular walking, and those who did some, but less than the recommendation (F = 5.0, P = 0.0137). Regular walkers were estimated to have a biologic ageing advantage associated with 6.5–7.6 years less biologic ageing compared to non-walkers, after adjusting for covariates. Additional investigations designed to study causality and the mechanisms associated with the walking and LTL relationship are needed.  相似文献   

公共健康视角下的电子竞技发展趋势研究     

闫金 《山东体育科技》2020,(1):11-15

电子竞技(E-sports)已经成为当代发展最快,且最重要的文化现象之一。国家体育总局于2003年将它列为第99个运动项目,又在2011年再次将电子竞技改为正式比赛项目。电子竞技从运动员、观众和经济价值而言,是一个不断发展的产业,而且它将被列入2024年巴黎奥运会。虽然最初主要是年轻男性对电子竞技感兴趣,但电子竞技有可能在更广泛的用户群体中带来健康行为的改变。本文运用文献资料法,对比分析法和逻辑分析法探讨电子竞技在整个生命周期内影响健康行为以及一些主要困境的解决措施。除此之外,电子竞技将有可能帮助于个人改变其体育活动和健康行为。最后考虑到电子竞技的指数增长,对于学者和政策制定者来说,认识到电子竞技带来的机遇是非常重要的。  相似文献   

Systematic Comparison of Decision Accuracy of Complex Compensatory Decision Rules Combining Multiple Tests in a Higher Education Context          下载免费PDF全文

Iris E. Yocarini  Samantha Bouwmeester  Guus Smeets  Lidia R. Arends 《Educational Measurement》2018,37(3):24-39

This real‐data‐guided simulation study systematically evaluated the decision accuracy of complex decision rules combining multiple tests within different realistic curricula. Specifically, complex decision rules combining conjunctive aspects and compensatory aspects were evaluated. A conjunctive aspect requires a minimum level of performance, whereas a compensatory aspect requires an average level of performance. Simulations were performed to obtain students' true and observed score distributions and to manipulate several factors relevant to a higher education curriculum in practice. The results showed that the decision accuracy depends on the conjunctive (required minimum grade) and compensatory (required grade point average) aspects and their combination. Overall, within a complex compensatory decision rule the false negative rate is lower and the false positive rate higher compared to a conjunctive decision rule. For a conjunctive decision rule the reverse is true. Which rule is more accurate also depends on the average test reliability, average test correlation, and the number of reexaminations. This comparison highlights the importance of evaluating decision accuracy in high‐stake decisions, considering both the specific rule as well as the selected measures.  相似文献   

Correlation analysis of performance measures for multi-label classification     

Rafael B. Pereira  Alexandre Plastino  Bianca Zadrozny  Luiz H.C. Merschmann 《Information processing & management》2018,54(3):359-369

In many important application domains, such as text categorization, scene classification, biomolecular analysis and medical diagnosis, examples are naturally associated with more than one class label, giving rise to multi-label classification problems. This fact has led, in recent years, to a substantial amount of research in multi-label classification. In order to evaluate and compare multi-label classifiers, researchers have adapted evaluation measures from the single-label paradigm, like Precision and Recall; and also have developed many different measures specifically for the multi-label paradigm, like Hamming Loss and Subset Accuracy. However, these evaluation measures have been used arbitrarily in multi-label classification experiments, without an objective analysis of correlation or bias. This can lead to misleading conclusions, as the experimental results may appear to favor a specific behavior depending on the subset of measures chosen. Also, as different papers in the area currently employ distinct subsets of measures, it is difficult to compare results across papers. In this work, we provide a thorough analysis of multi-label evaluation measures, and we give concrete suggestions for researchers to make an informed decision when choosing evaluation measures for multi-label classification.  相似文献   

试论当前我国扶贫的形势和对策     

李孝芳 《资源科学》1995,17(2):1-6

本文分析了我国当前扶贫工作的形势，提出扶贫工作的四个阶段，重点阐明了第四阶段的八项措施，指明当前扶贫工作中存在的主要问题。并提出尽快制定扶贫规划的建议。  相似文献   

Optimization of some factors affecting the performance of query expansion     

Young Mee Chung  Jae Yun Lee 《Information processing & management》2004,40(6):29

This paper examines the factors affecting the performance of global query expansion based on term co-occurrence data and suggests a way to maximize the retrieval effectiveness. Major parameters to be optimized through experiments are term similarity measure and the weighting scheme of additional terms. The evaluation of four similarity measures tested in query expansion reveal that mutual information and Yule's Y, which emphasize low frequency terms, achieve better performance than cosine and Jaccard coefficients that have the reverse tendency. In the evaluation of three weighting schemes, similarity weight performs well only with short queries, whereas fixed weights of approximately 0.5 and similarity rank weights were effective with queries of any length. Furthermore, the optimal similarity rank weight achieving the best overall performance seems to be the least affected by test collections and the number of additional terms. For the efficiency of retrieval, the number of additional terms needs not exceed 70 in our test collections, but the optimal number may vary according to the characteristics of the similarity measure employed.  相似文献