Transfer of momentum from different arm segments to a light movable target during a straight punch thrown by expert boxers

Abstract

Three modern views about the factors limiting oxygen uptake in healthy humans are set against the original (early 1920s) concept of A. V. Hill and colleagues. The majority view for most of the intervening time has been that cardiac output is the essential limiting function. Among recent research in support of this contention is that, in quadrupeds, pericardiectomy, which allows greater diastolic filling, elevates maximum oxygen uptake; however, the relevance to bipedal exercise can be questioned. In any case, algebraic analyses of model systems indicate that all identifiable stages on the oxygen transport pathway, from pulmonary diffusion to oxidative phosphorylation in skeletal muscle mitochondria, materially influence maximum uptake. Thus, if a high cardiac output is to be of benefit, all the other steps must function better too. Nevertheless, these two viewpoints concur that the limit to maximum oxygen uptake is somatic. In contrast, there are strong indications that at altitudes where oxygen availability is about half that at sea level, cerebral oxygenation is a limiting factor, and some recent experiments raise the possibility that it might be a substantial influence at sea level also. Clearly, consensus cannot yet be reached on the question posed in the title.     

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.     

Science Teachers' Inspiration for Teaching Socio‐scientific Issues: Disconnection with reform efforts

The need for the inclusion of socio‐scientific issues (SSI) into science curricula has been generally accepted, but relatively few science teachers have incorporated SSI into their courses. Most science teachers feel that their most important task by far is to teach the principles of science, and any substantive pedagogical changes represent a burden. Reformers and researchers often point out science teachers' lukewarm reactions to the reforms as a major barrier for educational changes but pay little attention to teachers' deeper values and inspirations. However, there are some teachers who address SSI out of their own personal initiative. Detailed case studies of four such teachers showed that although the teachers were aware of Science, Technology, Society or other reform efforts, they developed their own thrust and materials for SSI based on their own values, ideals, philosophies and personal concerns. This suggests that the current curriculum reforms (Science, Technology, Society, SSI, and Nature of Science) tend to suggest theoretical ideals, but do not effectively connect with teachers' deeper values and ideals.     

Aspects of a Practical Understanding: Heidegger at the workplace

This article aims to clarify some of our pre‐conceived assumptions when we address issues of learning in practice. It argues that we need to develop an understanding of practice based on its own premises. For this purpose the German philosopher Martin Heidegger's (1889–1976) understanding of practice and learning is introduced. Heidegger emphasises the use of equipment as crucial for a practical understanding. This perspective is contrasted with an intellectualistic approach to learning in practice exemplified by the work of Donald Schön. Heidegger and Schön's perspectives on learning in practice are evaluated and discussed throughout the article. Examples from studies of apprenticeship are used to illustrate Heidegger's comprehension of learning in practice. Especially learning through the use of tools and equipment, learning in context, learning as a consequence of making mistakes and learning as a matter of developing a sense of familiarity are types of learning emphasised in this article.     

A rhetorician's son: His advice to public speakers

J. M. Barrie's 1922 address Courageconstitutes a paradoxical rhetorical text. In his oratorical debut, Barrie offered seniors at St. Andrews poignant and explicit advice concerning life's liminal passages, even as he carefully obfuscated his own identity. This essay offers two readings of the text to illuminate an alternative relationship between text and context in rhetorical criticism. The first interpretation focuses on the obvious textual paradox related to liminality. The second reading moves from the “textual context” to the social and ideological context, and argues that working within the address is the rhetorical form of “the closet.” Recontextualizing Barrie's address from within “the closet,” renders visible a second “invisible context” related to homosexuality, opening a new interpretive doorway for the critic.