Spike jump biomechanics in male versus female elite volleyball players

ABSTRACT

There are well-known biological differences between women and men, especially in technical-coordinative variations that contribute to sex differences in performance of complex movements like the most important offensive action in volleyball, the spike jump. The aim of this study was to investigate sex-dependent performance and biomechanical characteristics in the volleyball spike jump. Thirty female and male sub-elite volleyball players were analysed while striking a stationary ball with maximal spike jump height. Twelve MX13 Vicon cameras with a cluster marker set, two AMTI force plates, surface EMG, and a Full-Body 3D model in Visual3D were used. Main findings include sex differences (P< .05) in jump height (pη² = .73), approach [speed (pη² = .61), step length], transition strategy [plant angle, neuromuscular activation (pη² = .91), horizontal force maxima and impulses], acceleration distances [centre of mass displacement (pη² = .21), minimal knee and hip angles], use of torso and arms [incline, angular velocity (pη² = .23)]. Correlations support that the results cannot be explained fully by strength and power differences between sexes but represent the product of technical-coordinative variations. Their relevance is acknowledged for both sexes and numerous performance determinants displayed sex differences. The integration of such attributes into sex-specific training seems promising but its effect requires further investigation.     

Writing quality in Chinese children: speed and fluency matter

There were two goals of the present study. The first was to create a scoring scheme by which 9-year-old Chinese children??s writing compositions could be rated to form a total score for writing quality. The second was to examine cognitive correlates of writing quality at age 9 from measures administered at ages 6?C9. Age 9 writing compositions were scored using a 7-element rubric; following confirmatory factor analyses, 5 of these elements were retained to represent overall writing quality for subsequent analyses. Measures of vocabulary knowledge, Chinese word dictation, phonological awareness, speed of processing, speeded naming, and handwriting fluency at ages 6?C9 were all significantly associated with the obtained overall writing quality measure even when the statistical effect of age was removed. With vocabulary knowledge, dictation skill, age, gender, and phonological awareness included in a regression equation, 35% of the variance in age 9 writing quality was explained. With the variables of speed of processing, speeded naming, and handwriting fluency additionally included as a block, 12% additional variance in the equation was explained. In addition to gender, overall unique correlates of writing quality were dictation, speed of processing, and handwriting fluency, underscoring the importance of both general automaticity and specific writing fluency for writing quality development in children.     

Developmental and individual differences in Chinese writing

The goal of the present study was to examine the generalizability of a model of the underlying dimensions of written composition across writing systems (Chinese Mandarin vs. English) and level of writing skill. A five-factor model of writing originally developed from analyses of 1st and 4th grade English writing samples was applied to Chinese writing samples obtained from 4th and 7th grade students. Confirmatory factor analysis was used to compare the fits of alternative models of written composition. The results suggest that the five-factor model of written composition generalizes to Chinese writing samples and applies to both less skilled (Grade 4) and more skilled (Grade 7) writing, with differences in factor means between grades that vary in magnitude across factors.     

An Educational Tool for Formal Relational Database Query Languages

This article describes an educational tool, implemented in Prolog, that takes advantage of the connection between logic programming and databases to provide an evaluator for relational query languages. The tool utilizes a common data definition facility and provides the student with a choice of query languages: relational algebra, domain relational calculus, tuple relational calculus, and SQL. The students use the relational interpreter for a sequence of homework assignments that both provide invaluable feedback on each language and illustrate the differences between the languages.     

Home Literacy Environments and Foundational Literacy Skills for Struggling and Nonstruggling Readers in Rural Early Elementary Schools

Factors such as weak early literacy skills and living in poverty may put young students at risk for reading disabilities. While home literacy activities and access to literacy materials have been associated with positive reading outcomes for urban and suburban students, little is known about home literacy environments of rural early elementary school students living in poverty and their relationship to foundational reading skills for struggling and nonstruggling readers. This study examined how home literacy environments might relate to rural kindergarten and first grade students’ reading performance. Parents of 1,108 kindergarten and first grade students in the rural Southeast completed questionnaires on the frequency of home literacy activities and access to literacy materials. Multilevel model analyses revealed that home literacy activities and access to literacy materials were positively related to basic word reading skills, passage comprehension, and spelling. Implications for families and educators are discussed.     

Machines,Media and Meaning

Ever since Icarus flew too high with his man-made wings, and suffered terrible consequences, warnings have been sounded to every would-be Daedalus who presumes to amplify human physical or intellectual powers by mechanical invention.     

全球化对职业技术教育的挑战及对策

当前,经济、政治、教育等社会诸领域的全球化已成为不可回避的大趋势。对社会进步及个体生存、发展而言,全球化的发展利弊同存,而通过加强职业技术教育有助于抓住机遇并减少其负面影响。本文阐述了由全球化在职业技术教育领域引起的新变化,并针对如何应对全球化带来的新挑战提出一些建议。