Effect of postural changes on 3D joint angular velocity during starting block phase     

Jean Slawinski  Raphaël Dumas  Laurence Cheze  Guy Ontanon  Christian Miller  Alice Mazure–Bonnefoy 《Journal of sports sciences》2013,31(3):256-263

Abstract

Few studies have focused on the effect of posture during sprint start. The aim of this study was to measure the effect of the modification of horizontal distance between the blocks during sprint start on three dimensional (3D) joint angular velocity. Nine trained sprinters started using three different starting positions (bunched, medium and elongated). They were equipped with 63 passive reflective markers, and an opto-electronic Motion Analysis® system was used to collect the 3D marker trajectories. During the pushing phase on the blocks, norm of the joint angular velocity (NJAV), 3D Euler angular velocity (EAV) and pushing time on the blocks were calculated. The results demonstrated that the decrease of the block spacing induces an opposite effect on the angular velocity of joints of the lower and the upper limbs. The NJAV of the upper limbs is greater in the bunched start, whereas the NJAV of the lower limbs is smaller. The modifications of NJAV were due to a combination of the movement of the joints in the different degrees of freedom. The medium start seems to be the best compromise because it leads, in a short pushing time, to a combination of optimal joint velocities for upper and lower segments.  相似文献   

The effect of individualised sprint training in elite female team sport athletes: A pilot study     

Elvir Rakovic  Gøran Paulsen  Christian Helland  Ola Eriksrud 《Journal of sports sciences》2013,31(24):2802-2808

ABSTRACT

This study aimed to evaluate whether an individualised sprint-training program was more effective in improving sprint performance in elite team-sport players compared to a generalised sprint-training program. Seventeen elite female handball players (23 ± 3 y, 177 ± 7 cm, 73 ± 6 kg) performed two weekly sprint training sessions over eight weeks in addition to their regular handball practice. An individualised training group (ITG, n = 9) performed a targeted sprint-training program based on their horizontal force-velocity profile from the pre-training test. Within ITG, players displaying the lowest, highest and mid-level force-velocity slope values relative to body mass were assigned to a resisted, an assisted or a mixed sprint-training program (resisted sprinting in the first half and assisted sprinting in the second half of the intervention period), respectively. A control group (CG, n = 8) performed a generalised sprint-training program. Both groups improved 30-m sprint performance by ~1% (small effect) and maximal velocity sprinting by ~2% (moderate effect). Trivial or small effect magnitudes were observed for mechanical outputs related to horizontal force- or power production. All between-group differences were trivial. In conclusion, individualised sprint-training was no more effective in improving sprint performance than a generalised sprint-training program.  相似文献   

Optimal Convert Strategies in Football     

Christian T. L. Janssen  Robert W. Schutz 《Research quarterly for exercise and sport》2013,84(4):339-344

Abstract

A frequently occurring situation in college and professional football is that of a team catching up through two touchdowns after trailing by 14 points, with the game outcome being determined by the extra-point plays. For leagues allowing two-point converts, an optimal point-after strategy exists under quite reasonable assumptions, and depends upon the relative utility to the team of a win, tie, or loss and the probability of success with a (one-point) kick as opposed to a (two-point) run/pass. We illustrate with reference to the January 1984 Orange Bowl game, where the favored team followed a possibly suboptimal strategy, losing the game and the national championship.  相似文献   

A Proposed Test for Determining Physical Working Capacity at the Heart Rate Threshold     

Loree L. Wagner  Terry J. Housh 《Research quarterly for exercise and sport》2013,84(3):361-364

Abstract

Forty-four subjects were given an all-out run test on a motor driven treadmill. The times for attaining heart rates of 150, 160, 170, 180 beats per minute were recorded along with measurements of ventilation, oxygen uptake and carbon dioxide production. The correlations between heart rate times and the all-out run times increased with the heart rate, a correlation of .85 calculated at the rate of 180 beats per minute. Using criteria established by Balke, it was demonstrated that the 180 heart rate serves as a valid cut-off point in measuring circulorespiratory capacity under variable exercise stress conditions.  相似文献   

The effects of differential and variable training on the quality parameters of a handball throw     

Herbert Wagner 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(1):54-71

The aim of this study was to undertake a comprehensive temporal, effective, and practical training study (variable and differential learning) that would offer athletes the opportunity to increase their performance, and to analyse the effects by measuring kinematics and quality parameters. Two participants of differing standards – a player of the first Austrian League and an Olympic and World Champion – but of similar anthropometric characteristics were recruited. One of the participants (Austrian League) was tested on five different occasions (pre-test and four retests) to measure the effects of four different training phases using kinematic analysis. The results of the study indicate an increase in ball velocity within the differential training phases (first, second, and fourth phases), different proximal-to-distal sequences of the participants, and a change of movement pattern during training measured by the segment velocities and the angle–time courses.  相似文献   

Quotenregelungen im Universit?tsgesetz - Eine verfassungsrechtliche und rechtspolitische Bewertung     

Michaela Wagner 《Zeitschrift für Hochschulrecht, Hochschulmanagement und Hochschulpolitik: zfhr》2012,11(5):167-183

Die trotz rechtlicher Gleichstellung bestehenden faktischen Ungleichgewichte zwischen den Geschlechtern in Bezug auf die Verteilung von Arbeitspl?tzen bzw Leitungsfunktionen führten im Bereich des ?ffentlichen Dienstes zur Einführung von Geschlechterquoten. Für die Universit?ten sehen das Universit?tsgesetz (UG) bzw das Bundes-Gleichbehandlungsgesetz (B-GlBG) die bevorzugte Aufnahme von Frauen einerseits in bestimmten Universit?tsgremien, andererseits bei der Besetzung von Stellen und bei Bef?rderungen innerhalb der universit?ren Strukturen vor. Der folgende Beitrag versucht die verfassungsrechtlichen Fragestellungen (Vereinbarkeit mit Gleichheitssatz, Bestimmtheitsgrundsatz) im Zusammenhang mit den Quotenregelungen des UG bzw des B-GlBG in concreto aufzuarbeiten bzw allgemein zur Frage der Gerechtigkeit und der rechtspolitischen Notwendigkeit von Quotenregelungen Stellung zu nehmen.  相似文献   

Ranking economists on the basis of many indicators: An alternative approach using RePEc data     

Christian Seiler  Klaus Wohlrabe 《Journal of Informetrics》2012,6(3):389-402

In economics the Research Papers in Economics (RePEc) network has become an essential source for the gathering and the spread of both existing and new economic research. Furthermore, it is currently the largest bibliometric database in economic sciences containing 33 different indicators for more than 30,000 economists. Based on this bibliographic information RePEc calculates well-known rankings for authors and academic institutions. We provide some cautionary remarks concerning the interpretation of some provided bibliometric measures in RePEc. Moreover, we show how individual and aggregated rankings can be biased due to the employed ranking methodology. In order to select key indicators describing and assessing research performance of scientist, we propose to apply principal component analysis in this data-rich environment. This approach allows us to assign weights to each indicator prior to aggregation. We illustrate the approach by providing a new overall ranking of economists based on RePEc data.  相似文献   

Free DNA – new potential analyte in clinical laboratory diagnostics?     

Wagner J 《Biochemia medica : ?asopis Hrvatskoga dru?tva medicinskih biokemi?ara / HDMB》2012,22(1):24-38

The existence of cell free DNA in the human circulatory system has been known since the 1950s, however, intensive research in this area has been conducted for the last ten years. This review paper brings a short overview of the existing literature concerning the cell free DNA research in various clinical fields and pathological states and considers the application possibilities of this new analyte in clinical laboratory diagnostics. At the moment, cell free DNA is most widely used for the purpose of non-invasive prenatal diagnosis of fetal sex or fetal RhD status. The recent discovery of epigenetic changes in placental/fetal DNA and the detection of fetal/placental-specific RNAs have made it possible to use this technology in all pregnancies irrespective of the gender of the fetus. With the application of new techniques such as next generation sequencing, digital PCR and mass spectrometry, it is now possible to detect very small amounts of specific DNA in the presence of excess of other nonspecific nucleic acids. Second most probable application is in oncology, where detection and monitoring of tumors is now possible by the detection of tumor-derived nucleic acids. Third promising field for near future implementation of this analyte is transplantation medicine, where free DNA level could serve as a marker of transplant rejection. Before any further utilization of this new biomarker, pre-analytical and analytical aspects of free DNA analysis remain to be standardized. In the field of noninvasive prenatal diagnosis, important ethical, legal and social questions remain to be discussed.  相似文献   

What limits [V(·)]O(2max)? A symposium held at the BASES Conference, 6 September 2010     

Spurway NC  Ekblom B  Noakes TD  Wagner PD 《Journal of sports sciences》2012,30(6):517-531

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.  相似文献   

Anthropometric, physiological, performance, and nutritional profile of the Brazil National Canoe Polo Team     

Alves CR  Pasqua L  Artioli GG  Roschel H  Solis M  Tobias G  Klansener C  Bertuzzi R  Franchini E  Lancha Junior AH  Gualano B 《Journal of sports sciences》2012,30(3):305-311

The purpose of this study was to determine the physiological, anthropometric, performance, and nutritional characteristics of the Brazil Canoe Polo National Team. Ten male canoe polo athletes (age 26.7 ± 4.1 years) performed a battery of tests including assessments of anthropometric parameters, upper-body anaerobic power (Wingate), muscular strength, aerobic power, and nutritional profile. In addition, we characterized heart rate and plasma lactate responses and the temporal pattern of the effort/recovery during a simulated canoe polo match. The main results are as follows: body fat, 12.3 ± 4.0%; upper-body peak and mean power, 6.8 ± 0.5 and 4.7 ± 0.4 W · kg(-1), respectively; 1-RM bench press, 99.1 ± 11.7 kg; peak oxygen uptake, 44.3 ± 5.8 mL · kg(-1) · min(-1); total energy intake, 42.8 ± 8.6 kcal · kg(-1); protein, carbohydrate, and fat intakes, 1.9 ± 0.1, 5.0 ± 1.5, and 1.7 ± 0.4 g · kg(-1), respectively; mean heart rate, 146 ± 11 beats · min(-1); plasma lactate, 5.7 ± 3.8 mmol · L(-1) at half-time and 4.6 ± 2.2 mmol · L(-1) at the end of the match; effort time (relative to total match time), 93.1 ± 3.0%; number of sprints, 9.6 ± 4.4. The results of this study will assist coaches, trainers, and nutritionists in developing more adequate training programmes and dietary interventions for canoe polo athletes.  相似文献