Coaching performance and leadership behaviours in team sports     

Stefan König 《Sportwissenschaft》2013,43(4):253-263

The aim of this study was to investigate coaching performance in team sports taking leadership behaviours into focus. To do so, coaching performance was put in a literature-based frame and analysed with reference to a task structure based on the idea of hierarchical planning. The focus of the paper is on a mixed methods multi-strand study using qualitative as well as quantitative threads to develop and verify a set of coaching strategies focussing on teambuilding and team leadership. Qualitative analyses showed that coaches do have a clear understanding of forming and leading a team, which could be shown by a specific set of strategies being used by high performance coaches from different team sports (basketball, football, handball, and volleyball). These strategies could be confirmed in a sequential quantitative study analysing coaches’ and players’ attitudes towards the previously analysed schemes. The results of this study are discussed in terms of methodical and practical implications.  相似文献   

Alterations in Body Size and Composition Consequent to Astro-Trimmer and Slim-Skins Training Programs     

Jack H. Wilmore  Anne E. Atwater  Bess D. Maxwell  Dorothy L. Wilmore  Stefan H. Constable  Michael J. Buono 《Research quarterly for exercise and sport》2013,84(1):90-92

Tennis is an activity requiring both endurance and anaerobic components, which could have immunosuppressive effects postexercise.

Purpose

The purpose of this investigation was to determine the effect of a simulated tennis match on apoptotic and migratory markers on lymphocyte subsets.

Method

Male high school (n = 5) and college (n = 3) tennis players (M _age = 18.9 ± 3.3 years) completed 10 sets of a tennis protocol including serves, forehand strokes, and backhand groundstrokes with 1-min rest periods between sets. Apoptosis antigen 1 receptor (CD95) and chemokine receptor fractalkine (CX₃CR1) expression was analyzed on helper T lymphocytes (CD4+), cytotoxic T lymphocytes (CD8+), and B lymphocytes (CD19+) twice, at resting baseline and immediately after all 10 sets of the tennis protocol.

Results

An increase was observed in each lymphocyte subtype (p < .02, effect size = .41), and comparison of absolute changes revealed increases in CD4+/CD95+, CD8+/CD95+, and CD8+/CX₃CR1 lymphocytes following the tennis protocol (p < .01, effect size = .43), but not in CD19+ cells.

Conclusions

A simulated tennis match has adequate intensity to induce immune modulations in terms of increased cell death and cellular migration in T lymphocyte subsets. Lymphocytopenia following tennis play is influenced by both apoptotic and migratory mechanisms.  相似文献   

Cycling power output produced during flat and mountain stages in the Giro d'Italia: A case study     

Stefan Vogt  Yorck Olaf Schumacher  Andreas Blum  Kai Roecker  Hans-Hermann Dickhuth  Andreas Schmid 《Journal of sports sciences》2013,31(12):1299-1305

Abstract

Until recently, the physiological demands of cycling competitions were mostly reflected by the measurement of heart rate and the indirect estimation of exercise intensity. The purpose of this case study was to illustrate the varying power output of a professional cyclist during flat and mountain stages of a Grand Tour (Giro d'Italia). Nine stage recordings of a cyclist of the 2005 Giro d'Italia were monitored using a mobile power measurement device (SRM Trainingssystem, Julich, Germany), which recorded direct power output and heart rate. Stages were categorized into flat (n = 5) and mountain stages (n = 4). Data were processed electronically, and the overall mean power in flat and mountain stages and maximal mean power for various durations were calculated. Mean power output was 132 W ± 26 (2.0 W · kg^?1 ± 0.4) for the flat and 235 W ± 10 (3.5 W · kg^?1 ± 0.1) for the mountain stages. Mountain stages showed higher maximal mean power (367 W) for longer durations (1800 s) than flat stages (239 W). Flat stages are characterized by a large variability of power output with short bursts of high power and long periods with reduced intensity of exercise, whereas mountain stages mostly require submaximal, constant power output over longer periods.  相似文献   

Regulation and deregulation in education policy: new reforms and school sports in Swedish upper secondary education     

Stefan Lund 《Sport, Education and Society》2013,18(3):241-257

During the 1990s, neoliberal reforms in Sweden increased local school actors' possibilities to develop school profiles regarding both organization and content. This restructuring has increased the total number of school sports programs as well as the possibilities for upper secondary schools and sports clubs to develop elite and amateur sports on a local level. In a new educational reform, the Swedish Government criticizes parts of the Swedish school sports system. The Government believes that the majority of local school sports programs and courses obstruct the maintenance of national equivalence, that upper secondary schools use school sports to attract pupils for economic reasons and that some pupils involved in school sports may fail to reach the academic or vocational goals of regular upper secondary education. Using critical discourse analysis, the present paper illustrates how educational policies are linked to wider symbolic meaning systems in an attempt to legitimize, define and organize upper secondary schools and to characterize pupils as either eligible or ineligible to participate in school sports. The analyses are based on various types of empirical data: policy documents, official letters from the sports movement on the government bill and in-depth interviews. The results indicate that the reform represents a shift in the policy rhetoric: from a normative rhetoric highlighting pupils' social and emotional reasons for choosing school sports, to a rational rhetoric emphasizing efficiency, standardization and regulation of pupils' educational choices. Using school sports as an example, the paper shows how the main aim of the reform—to raise educational standards and maintain national equivalence—is achieved through social differentiation, meaning that pupils with the right performance indicators are selected for participation in programs to which they are suited.  相似文献   

Technical possibilities for optimising the ski-binding-boot functional unit to reduce knee injuries in recreational alpine skiing     

Veit Senner  Frank I. Michel  Stefan Lehner  Othmar Brügger 《Sports Engineering》2013,16(4):211-228

This review study focuses on knee injuries in recreational alpine skiing. The objectives of this study were (1) to provide selected knowledge derived from current and past knee injury epidemiology; (2) to outline the most important knee injury mechanisms; and (3) to review and discuss how modifications of the skiing equipment might alleviate the risk of knee injuries. This review represents the essence of a comprehensive research report and considers the content of more than 230 scientific papers, further “grey literature”, patents, international standards and other publications. Knee injuries are the most frequent injuries in alpine skiing and their incidence rate remained high despite a decline of the incidence of other skiing injuries in recent years. Women have a higher knee injury risk, but age and tiredness appear not to be significant factors. Apart from the commonly described injury mechanisms “phantom foot” and “boot-induced anterior drawer” other more sophisticated injury categorisations are given. The ski radius, the ski length and the standing height on the ski may be relevant ski parameters. For the binding, the release mechanisms in different mechanical degrees of freedom, the impact tolerance and the maintenance frequency are discussed. In the ski boot, the height of the upper, the boot liner, the shaft stiffness, and the position on the ski may play a role. The biggest challenge, but probably also the biggest opportunity for a reduction of knee injury rates seems to be the development of a mechatronic binding. The current strategies to develop these types of bindings are explained and illustrated by one example. Some of the possible parameters which may be essential for the necessary control algorithms are described. Finally, considerations regarding the strategic and operational implication of the analysed technical measures are given.  相似文献   

Kinematic differences of elite and high-performance tennis players in the cross court and down the line forehand     

Johannes Landlinger  Stefan Josef Lindinger  Thomas Stöggl  Herbert Wagner  Erich Müller 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(4):280-295

This study identified and compared the full body kinematics of different skill levels in the forehand groundstroke when balls were hit cross court and down the line. Forty-three three-dimensional retro-reflective marker trajectories of six elite and seven high-performance players were recorded using an eight-camera 400 Hz, Vicon motion analysis system. The six highest horizontal velocity forehands with reliable kinematics of all participants were analysed for each specific situation (a total of 156 analysed shots). Significant differences (p < 0.01) and large effect sizes were observed between elite and high-performance players in linear velocity of the shoulder (2.0 vs. 1.2 m/s), angular velocity of the pelvis (295 vs. 168 °/s), and angular velocity of the upper trunk (453 vs. 292 °/s) at impact. The elite group showed a tendency towards higher racquet velocities at impact (p < 0.05). No significant differences were found in angular displacement of the racquet, hip alignment, or shoulder alignment at the completion of the backswing; nor did angular displacement vary significantly at impact. Irrespective of the group, different shoulder, hip, and racquet angles were found at impact, depending on the situation. The results should assist coaches when striving to improve their players' forehand.  相似文献   

Students’ formative assessment perceptions,feedback use and mathematics performance in secondary schools in Tanzania     

Florence Kyaruzi  Jan-Willem Strijbos  Stefan Ufer  Gavin T. L. Brown 《Assessment in Education: Principles, Policy & Practice》2019,26(3):278-302

This study investigates the impact of secondary school students’ perceptions of mathematics teachers’ formative assessment practices and feedback delivery on their feedback use, and mathematics performance. The sample consisted of 2767 Form 3 (Grade 11) students from 48 secondary schools in Tanzania. Surveys and focus group discussions were used to measure students’ perceptions of formative assessment, feedback delivery, and feedback use. Structural Equation Modelling (SEM) of survey data showed that students’ perceptions of the quality of teacher feedback delivery and perceived scaffolding positively predicted students’ feedback use whereas perceived monitoring negatively predicted feedback use. In turn, students’ feedback use positively predicted their mathematics performance to a small extent. Content analysis of focus group discussions illustrated that most students valued their mathematics teacher’s assessment practices. The findings imply that in Sub-Saharan African educational systems the quality of teacher feedback delivery and promotion of student feedback use can improve students’ mathematics performance.  相似文献   

Expression of a fusion protein of human ciliary neurotrophic factor and soluble CNTF-Receptor and identification of its activity     

孙益  葛霁光 《浙江大学学报(A卷英文版)》2003,4(3):340-345

Ciliary neurotrophic factor (CNTF) has pleiotropic actions on many neuronal populations as well as on glia. Signal transduction by CNTF requires that it bind first to CNTF-R, permitting the recruitment of gp130 and LIF-R, forming a tripartite receptor complex. Cells that only express gp130 and LIF-R, but not CNTF-R are refractory to stimulation by CNTF. On many target cells CNTF only acts in the presence of its specific agonistic soluble receptors. We engineered a soluble fusion protein by linking the COOH-terminus of sCNTF-R to the NH₂-terminus of CNTF. Recombinant CNTF/sCNTF-R fusion protein (Hyper-CNTF) was successfully expressed in COS-7 cells. The apparent molecular mass of the Hyper-CNTF protein was estimated from western blots to be 75 kDa. Proliferation assays of transfected BAF/3 cells in response to CNTF and Hyper-CNTF were used to verify the activity of the cytokines. The proliferative results confirmed that CNTF required homodimerization of the gp130, CNTF-R and LIF-R receptor subunit whereas Hyper-CNTF required heterodimerization of the gp130 and LIF-R receptor subunit. We concluded that the fusion protein Hyper-CNTF had superagonistic activity on target cells expressing gp130 and LIF-R, but lacking membrane-bound CNTF-R. Project supported by the Scientific Research Foundation for the Returned Overseas Chinese Scholar, Zhejiang Province, China and SFB415, TP B5, Germany.  相似文献   

Posthumanism and the massive open online course: contaminating the subject of global education     

Stefan Herbrechter 《Distance Education》2016,37(3):376-379

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The myth of global science collaboration—Collaboration patterns in epistemic communities     

Stefan Hennemann  Diego Rybski  Ingo Liefner 《Journal of Informetrics》2012,6(2):217-225

Scientific collaboration is often perceived as a joint global process that involves researchers worldwide, regardless of their place of work and residence. Globalization of science, in this respect, implies that collaboration among scientists takes place along the lines of common topics and irrespective of the spatial distances between the collaborators. The networks of collaborators, termed ‘epistemic communities’, should thus have a space-independent structure. This paper shows that such a notion of globalized scientific collaboration is not supported by empirical data. It introduces a novel approach of analyzing distance-dependent probabilities of collaboration. The results of the analysis of six distinct scientific fields reveal that intra-country collaboration is about 10–50 times more likely to occur than international collaboration. Moreover, strong dependencies exist between collaboration activity (measured in co-authorships) and spatial distance when confined to national borders. However, the fact that distance becomes irrelevant once collaboration is taken to the international scale suggests a globalized science system that is strongly influenced by the gravity of local science clusters. The similarity of the probability functions of the six science fields analyzed suggests a universal mode of spatial governance that is independent from the mode of knowledge creation in science.  相似文献