Mechanical determinants of acceleration and maximal sprinting speed in highly trained young soccer players     

Martin Buchheit  Pierre Samozino  Jonathan Alexander Glynn  Ben Simpson Michael  Hani Al Haddad  Alberto Mendez-Villanueva 《Journal of sports sciences》2014,32(20):1906-1913

Abstract

The aim of the present study was to examine, in highly trained young soccer players, the mechanical horizontal determinants of acceleration (Acc) and maximal sprinting speed (MSS). Eighty-six players (14.1 ± 2.4 year) performed a 40-m sprint to assess Acc and MSS. Speed was measured with a 100-Hz radar, and theoretical maximal velocity (V₀), horizontal force (F₀) and horizontal power (P_max) were calculated. Within each age group, players were classified as high Acc/fast MSS (>2% faster than group mean), medium (between ?2% and +2%), and low/slow (>2% slower). Acc and MSS were very largely correlated (?0.79; 90% confidence limit [?0.85; ?0.71]). The determinants (multiple regression r² = 0.84 [0.78; 0.89]) of Acc were V₀ (partial r: 0.80 [0.72; 0.86]) and F₀ (0.57 [0.44; 0.68]); those of MSS (r² = 0.96 [0.94; 0.97]) were V₀ (0.96 [0.94; 0.97]) and P_max (0.73 [0.63; ?0.80]). High/Med have likely greater F₀ (Cohen’s d: +0.8 [0.0; 1.5]), V₀ (+0.6 [?0.1; 1.3]) and P_max (+0.9 [0.2; 1.7]) than Low/Med. High/Fast have an almost certainly faster V₀ (+2.1 [1.5; 2.7]) and a likely greater P_max (+0.6 [?0.1; 1.3]) than High/Med, with no clear differences in F₀ (?0.0 [?0.7; 0.6]). Speed may be a generic quality, but the mechanical horizontal determinants of Acc and MSS differ. While maximal speed training may improve both Acc and MSS, improving horizontal force production capability may be efficient to enhance sprinting performance over short distances.  相似文献   

The missing link: an econometric analysis on the impact of curriculum standards on student achievement     

Nicola A. Alexander   《Economics of Education Review》2000,19(4):752

Nationwide, state policy-makers have increasingly adopted curriculum standards as a means of improving education. However, relatively little empirical research has been done to investigate if a link actually exists between curriculum standards and student performance. Using data collected by the New York State Department of Education, the impact of standards on high school student achievement is examined through estimation of a one-way fixed-effects model of the education production function. Curriculum standards are operationalized as the award of a “50–64” variance, which is considered a means of increasing the number of students taking demanding courses. The findings suggest that curriculum standards can improve student performance, but they do little to improve equity. While larger portions of pupils pass curriculum-based assessment exams, continued associations between select student characteristics and student performance remain.  相似文献   

Indeed,sometimes knowledge does not help: A replication study     

Stark  Robin  Gruber  Hans  Mandl  Heinz  Renkl  Alexander 《Instructional Science》1998,26(5):391-407

In an earlier study we found that intermediate experts in the domain of economics did not surpass novices in complex learning and knowledge application with a computer-based business simulation. In the present study, it was investigated whether these contra-intuitive findings can be replicated. In order to scrutinize the reasons which led to these findings, some parameters of the learning environment were changed. The duration of the exploration phase and of the problem-solving phase as well as the complexity of the situations were increased, motivation and acquired declarative knowledge were assessed. In view of mastering recurring demands and the functionality of mental models, no differences were found between a group of novices (15 students of humanities with a supplementary training in economics) and a group of intermediate experts (13 advanced students of economics). The findings of the original study were replicated, motivation had no effect on the result. In terms of declarative knowledge, the novices turned out to be even better.  相似文献   

Organizational Culture and Socio‐cultural Values: Perceptions of Managers and Employees in Five Economies in Transition     

Maria Cseh  Alexandre Ardichvili  Alexander Gasparishvili  Bla Krisztin  Zsolt Nemeskeri 《Performance Improvement Quarterly》2004,17(2):5-27

This survey‐based study compared socio‐cultural values and perceptions of organizational culture characteristics held by more than 3,300 managers and employees in twelve business organizations in Hungary, Russia, Georgia, Kazakhstan, and the Kyrgyz Republic. Significant differences were found between the five countries on all socio‐cultural and organizational culture dimensions. The relationship between socio‐cultural values and the organizational culture perceptions was only moderately significant. The paper concludes with implications for professionals seeking to enhance organizations' performance in these countries and suggestions for further research.  相似文献   

A Perspective on Strategy Research: Progress and Prospects     

Patricia A. Alexander  Steven Graham  Karen R. Harris 《Educational Psychology Review》1998,10(2):129-154

Our goal in this article is to present a broad perspective on the state of strategy research and to consider, in brief, the prospects for strategy research in the future. We first draw on the literature in an effort to delineate the attributes of strategies and to consider several dimensions of strategies that dot the research landscape. Next, we distinguish strategic performance from skillful behavior. With this definitional framework in place, we survey changes that might be evidenced in learners' strategic processing over time, as a consequence of knowledge and motivation, as well as other personal factors. Additionally, we explore aspects of the task and the context that serve as change agents in strategy development, including domain, time, and instructional support. We conclude with a brief reflection on issues that deserve attention in research and practice in the next decade, to assist strategies instruction in reaching its potential as a part of integrated, validated instructional practices.  相似文献   

Do students notice stress in teachers? Associations between classroom teacher burnout and students' perceptions of teacher social–emotional competence     

Eva Oberle  Alexander Gist  Muthutantrige S. Cooray  Joana B. R. Pinto 《Psychology in the schools》2020,57(11):1741-1756

The goal of the present study was to investigate the link between elementary school teacher burnout and students' perceptions of teacher social–emotional competence (SEC). A total of 676 Grades 4–7 students in 35 classrooms rated their classroom teachers' SEC. In addition, teachers self-reported their current level of experienced burnout at work (i.e., depersonalization and emotional exhaustion). Multilevel analyses revealed significant classroom-level variability (i.e., 34%) in student-ratings of teacher SEC. Teacher burnout significantly predicted student-rated teacher SEC, over and above significant student-level variables (school self-concept, sense of autonomy in the classroom) and contextual variables (teacher age, school neighborhood income). Specifically, higher levels of teacher burnout were related to receiving lower SEC ratings by students. Teacher burnout explained a significant portion of the classroom-level variability in student-rated teacher SEC. The present study emphasizes the link between teacher burnout and the SEC. Furthermore, given that teacher reports (burnout) were linked to student reports (teacher SEC), these findings also suggest that students notice stress in their classroom teacher.  相似文献   

The mirror’s curse: Weight perceptions mediate the link between physical activity and life satisfaction among 727,865 teens in 44 countries     

Silvia Meyer  Rebekka Weidmann  Alexander Grob 《运动与健康科学(英文)》2021,10(1):48-54

Purpose:The present study aimed to examine the link between physical activity(PA)and life satisfaction in a large international study of adolescents.We also aimed to test whether overweight and underweight perceptions act as mediators and whether age and sex acted as moderators.Methods:For this purpose,we analyzed data from the Health Behavior in School-aged Children study,which comprises 727,865 observations from 44 nations at 4 measurement occasions.Results:Multilevel analyses revealed a positive link between PA and life satisfaction.In addition,underweight and overweight perceptions mediated the effect of PA on life satisfaction.We further found that age and sex acted as moderators.In older adolescents,stronger effects were found in the links between PA and life satisfaction,PA and overweight perception,and both weight perceptions and life satisfaction.In addition,in female adolescents,the link between overweight perception and life satisfaction was stronger.Conversely,the links between PA and both weight perceptions were stronger for boys.Conclusion:The results suggest that weight perception explains part of the relationship between PA and life satisfaction in adolescents and that these effects vary as a function of age and sex.  相似文献   

Forgeries of Fossils in “Amber”: History,Identification and Case Studies     

David A. Grimaldi  Alexander Shedrinsky  Andrew Ross  Norbert S. Baer 《Curator: The Museum Journal》1994,37(4):251-274

The appeal of ancient fossilized tree resin, or amber, has made pieces with animal and plant inclusions particularly prized. Unfortunately, amber forgeries are more convincingly and routinely made than most other kinds of fossils, by embedding organisms in natural resins (e.g., copal) or synthetic resins (especially polyester) or by filling a carved niche in a natural piece of amber with resin and a modern inclusion. The confusion of organisms in copal (forged and natural) for ones in amber has a long history. Reviewed here are simple tests for discerning forgeries and natural inclusions in both substances. We discuss an old but sophisticated technique for crafting amber forgeries from authentic amber and present several new examples from old collections in two large museum collections. Also discussed is the widespread use of polyester resin forgeries in the Dominican Republic and Mexico.  相似文献   

Drivers and barriers to the utilisation of gamification and game-based learning in universities: A systematic review of educators' perspectives     

Danielle Lester  Gregory J. Skulmoski  Darren P. Fisher  Vishal Mehrotra  Iris Lim  Alexander Lang  Justin W. L. Keogh 《British journal of educational technology : journal of the Council for Educational Technology》2023,54(6):1748-1770

While gamification and game-based learning have both been demonstrated to have a host of educational benefits for university students, many university educators do not routinely use these approaches in their teaching. Therefore, this systematic review, conducted using the PRISMA guidelines, sought to identify the primary drivers and barriers to the use of gamification and game-based learning by university educators. A search of multiple databases (Web of Science, Scopus and EBSCO (Business Source Complete; ERIC; Library, Information Science & Technology Abstracts)) identified 1330 articles, with 1096 retained after duplicates were removed. Seventeen articles (11 quantitative, two mixed-methods and four qualitative) were included in the systematic review. The primary drivers described by the educators that positively influenced their gamification and game-based learning usage were their beliefs that it encourages student interactions and collaborative learning; provides fun and improves engagement; and can easily be used by students. Alternatively, the university educators' major barriers included a lack of time to develop gamification approaches, lack of proven benefits and classroom setting issues. Many of these and other less commonly reported drivers and barriers can be categorised as attitudinal, design-related or administrative in nature. Such categorisations may assist university educators, teaching support staff and administrators in better understanding the primary factors influencing the utilisation of gamification and game-based learning and develop more effective strategies to overcome these barriers to its successful implementation.

Practitioner notes

What is already known about this topic

• Gamification and game-based learning may have many benefits for university students.
• The majority of university educators do not routinely use gamification and game-based learning in their teaching.

What this paper adds

• University educators' major drivers that positively influence the use of gamification and game-based learning include their perceptions that it encourages student interactions and collaborative learning, provides fun and improves engagement and can easily be used by students.
• University educators' major barriers that negatively influence the use of gamification and game-based learning include their perceptions of a lack of time to develop gamification approaches, lack of proven benefits and classroom setting issues.
• These drivers and barriers may be classified as attitudinal, design-related and administrative, with these categories providing a useful way for universities to develop strategies to better support educators who wish to use these approaches in their teaching.

Implications for practice and policy

• Attitudinal factors such as university educators' intention to use gamification and game-based learning are influenced by a host of their perceptions including attitude, perceived usefulness and ease of use.
• A range of design-related and administrative barriers may need to be overcome to increase the use of gamification and game-based learning in the university sector.

  相似文献   

Leadership Styles of Russian Enterprise Managers: The Effect of Transactional and Transformational Behaviors on Employees' Evaluation of Managerial Performance     

Alexander Ardichvili 《Performance Improvement Quarterly》2001,14(1):96-117

The purpose of this research was to identify leadership styles of today's Russian enterprise managers and to determine how these styles are related to employees' subjective evaluation of managerial performance. The survey was based on Bass and Avolio's MLQ5x leadership styles instrument. Valid responses were received from 1,216 managers and employees at three large manufacturing enterprises located in Moscow. The study results suggest that Russian managers used three well‐known leadership styles—transactional, transformational, and laissez‐faire. However, the laissez‐faire style was not prevalent. Overall, transactional leadership was used more often than transformational leadership. Transactional contingent ceward leadership was used more often than any other approaches. Charisma and Individualized Consideration have received the lowest scores among the transformational leadership style dimensions. Tests of the relationship between leadership styles and managerial performance measures indicate that transformational leadership‐and one of its components, Charisma‐had the strongest relationship with positive outcomes. Implications for developing leadership training programs in Russia and for the transfer of Western training and development approaches are discussed.  相似文献