The role of path length- and speed-related factors for the enhancement of section performance in alpine giant slalom     

Jörg Spörri  Josef Kröll  Hermann Schwameder  Erich Müller 《European Journal of Sport Science》2018,18(7):911-919

Knowing how to enhance alpine skiing performance is essential for effective coaching. The purpose of this study was to explore the role of path length- and speed-related factors for performance enhancement, while skiing on a homogeneously set/constantly inclined giant slalom course section (average gate distance: 27?m; offset: 8?m; slope inclination: 26°). During a video-based three-dimensional kinematic field-experiment, the data of six athletes who skied a two-gate section on four different types of skis were collected. The performance parameter analysed was section time. The performance predictors analysed were centre of mass (CoM), path length and the change in specific mechanical energy per entrance speed along the analysed section. Furthermore, since the current study examined alpine skiing performance within short sections, the skier’s entrance speed was also considered. Classified as a high-performance and a low-performance group based on section time, slow and fast trials significantly differed in CoM path length, the change in specific mechanical energy per entrance speed and entrance speed. The entrance speed of all trials analysed ranged between 15.25 and 17.66?m/s. In trials with both high and low entrance speed, the change in specific mechanical energy per entrance speed was found to be more relevant for the prediction of section time than CoM path length. However, further studies should investigate whether such a prioritization can be unrestrictedly generalized to other situations, such as entrance speeds, course sets, slope inclinations and competition disciplines different to those assessed in the current study.  相似文献   

Kinematic analysis of proximal-to-distal and simultaneous motion sequencing of straight punches     

Philip Xaver Fuchs  Stefan Josef Lindinger  Hermann Schwameder 《Sports biomechanics / International Society of Biomechanics in Sports》2018,17(4):512-530

Consecutive proximal-to-distal sequencing of motion is considered to be integral for generating high velocity of distal segments in many sports. Simultaneous usage of proximal and distal segments as seen in martial arts is by far less well investigated. Therefore, the aim of the study was to characterise and differentiate the concepts of consecutive (CSM) and simultaneous (SSM) sequence of motion in straight reverse punches as practised in Practical Wing Chun. Four experienced martial artists succeeded an eligibility test for technical proficiency in both concepts and performed a total number of 20 straight punches per concept. Eight MX13 Vicon cameras (250 fps) and Visual3D were used for motion capture and analyses. Both motion concepts showed proximal-to-distal sequencing of maximal joint velocities but, in SSM, this was coupled with simultaneous initiation. Key characteristics were: high pelvis momentum and backswing of shoulder and elbow (CSM); and importance of shoulder involvement (SSM). Different ranges of motion, timing aspects and achieved maximal angular velocities distinguished both concepts, which led to differences (p < 0.05) in fist velocity at contact, execution time, distance and horizontal shift of the centre of mass. Proper application of both concepts depends on the environmental setting, situational requirements and individual fighting style.  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   

Training transfer between card sorting and false belief understanding: helping children apply conflicting descriptions   总被引：2，自引：0，他引：2  

Kloo D  Perner J 《Child development》2003,74(6):1823-1839

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TEACHING INDUCTIVE THINKING TO HIGHLY ABLE CHILDREN     

Karl Josef Klauer 《High Ability Studies》1992,3(2):164-180

Two criteria were used to identify highly able kindergarten children: assessment by teachers and an IQ ≥ 115 on Raven's Progressive Matrices. In this way, 16 highly able children were found, matched pairwise according to age and IQ, and then randomly allotted to two treatment conditions. In one condition the children were trained using a program for fostering inductive thinking, whereas the children in the other condition continued their normal kindergarten activities. Based upon a new theory of inductive reasoning, the training was expected to have a positive effect on intelligence test performance. Results showed that all of the trained children outperformed their matched counterparts. It was concluded that, even with highly able children, the level of cognitive functioning can be improved, and that training of inductive thinking is an effective means to this end.  相似文献   

Alternative models of entrance exams and access to higher education: the case of the Czech Republic     

Tomá? Kone?ny  Josef Basl  Jan Myslive?ek  Natalie Simonová 《Higher Education》2012,63(2):219-235

The study compares the potential effects of a university admission exam model based on program-specific knowledge and an alternative model relying on general study aptitude (GSA) in the context of a strongly stratified educational system with considerable excess of demand over supply of university education. Using results of the Sonda Maturant 1998 survey, we show that in the specific context of the Czech Republic, displaying the above characteristics in the given period, an admission exam model based on general study aptitude tests may improve the access of talented individuals with lower socioeconomic status to university education. Our simulations show that with the GSA model (provided the model assumptions are met), the relative chances of an applicant with a university-educated father would be only by one-fourth higher than the relative chances of a student with a less educated father, as compared to the more than a one-third difference in case of the model emphasizing program-specific knowledge. The odds ratio for the GSA model is by 28% points lower for mother’s education.  相似文献   

Meetings of Directors of the National Libraries in the socialist countries held in, 1967–1968     

Josef Vinárek 《International Information and Library Review》2013,45(1):89-91

Abstract

The years 1989–91 saw tremendous changes in the political map of Eastern Europe. These changes have resulted in varying degrees of acquisition difficulties for Slavic and Eastern European language collections in Western libraries. The following is an early assessment of the difficulties and the resultant damage done to Slavic collections in the West. Preliminary results show that, on the whole, book receipts are down considerably, prices are up considerably, and inconsistency is the only consistency. The data discussed here were gathered by means of a survey of certain aspects of Slavic¹ acquisitions. These data are supplemented throughout by qualitative material gleaned from comments made by vendors and librarians at the 1993 Slavic Librarians' Workshop held at Urbana, Illinois.  相似文献   

Travelling the Unpaved Road to Democracy from Communism: A Cross‐Cultural Perspective on Change     

Josef A. Mestenhauser 《Higher Education in Europe》1998,23(1):83-137

The basic subject of this article is change, how one copes with it, how it can or cannot be guided. More specifically, the author, a Czech‐American scholar, examines the processes and the trauma of the post‐1989 transition in his country of birth with an eye to how education, particularly higher education, can contribute to a successful outcome to transition affecting all of society while undergoing transition itself. Crucial to the presentation and arguments of the author is his conviction that the period of communist rule in Czechoslovakia, as in the other central and eastern European countries, was intellectually and morally damaging. For the citizens of the Czech Republic as well as for those of the other central and eastern European countries who also experienced communism and who are now trying to recover from it, it is necessary that they develop a clear understanding of what communism really represented and what it did to them. For them to gain this understanding, the catharsis that goes with it, and the possibility of developing successful reforms that will move their countries forward in a constructive way, they must develop a number of cross‐cultural skills through familiarity with a number of social science and educational disciplines that were more‐or‐less closed to them. The author proposes ways in which these skills can be learned and education at all levels profoundly reformed.  相似文献   

Sum of squares of deviations     

Josef Bukac  Jakub Sulc 《Teaching Statistics》2020,42(1):30-31

The question is whether or not we or any student are allowed to define a measure of variability in some other way that is not written in textbooks and officially approved. We compare the sum of squares of all deviations against the usual sum of squares of deviations from the mean.  相似文献   

TRANSFORMING CZECH HIGHER EDUCATION AND RESEARCH     

Josef Jarab 《Higher Education in Europe》1995,20(3):103-110

The process which got underway after the Velvet Revolution to transform Czech higher education had first to confront the fact that a good deal of desired continuity existed. The first reform law was hastily conceived, and the reform process has been hampered by insufficient funding. The possibilities of introducing tuition fees in the state institutions and of founding private universities are being debated in Parliament Both innovations would represent a major cultural change. The reform process has been aided by the contributions of western governmental and non‐governmental organizations.  相似文献