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91.
The aims of the present study were (1) to analyse the physical demands of top-class referees and (2) to compare their official FIFA fitness test results with physical performance during a match. The work rate profiles of 11 international referees were assessed during 12 competitive matches at the 2003 FIFA Under-17 World Cup and then analysed using a bi-dimensional photogrammetric video analysis system based on direct lineal transformation (DLT) algorithms. In the first 15 min of matches, the referees were more active, performing more high-intensity exercise (P < 0.01) than in the first 15 min of the second half. During the second half of matches, the referees covered a shorter distance (P < 0.01), spent more time standing still (P < 0.05), and covered less ground cruising (P < 0.05), sprinting (P < 0.05), and moving backwards (P < 0.001) than in the first half. Also in the second 45 min, the distance of referees from infringements increased (P < 0.05) in the left attacking zone of the filed. There was also a decrease (P < 0.05) in performance in the period following the most high-intensity activity, compared with the mean for the 90 min. Time spent performing high-intensity activities during a match was not related to performance in the 12-min run (r(2) = 0.30; P < 0.05), the 200-m sprint (r(2) = 0.05; P < 0.05), or the 50-m sprint (r(2) = 0.001; P < 0.05). The results of this study show that: (1) top-class referees experienced fatigue at different stages of the match, and (2) the typical field tests used by FIFA (two 50-m and 200-m sprints, followed by a 12-min run) are not correlated with match activities. 相似文献
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Jacobien H.F. Oosterhoff Vincent Gouttebarge Maarten Moen J. Bart Staal Gino M.M.J. Kerkhoffs Johannes L. Tol 《Journal of sports sciences》2019,37(2):131-137
The objective was to systematically review the literature on risk factors and prevention programs for musculoskeletal injuries among tennis players. PubmedMedline, Embase, CINAHL, Cochrane, SportDiscus were searched up to February 2017. Experts in clinical and epidemiological medicine were contacted to obtain additional studies.
For risk factors, prospective cohort studies (n > 20) with a statistical analysis for injured and non-injured players were included and studies with a RCT design for prevention programs. Downs&Black checklist was assessed for risk of bias for risk factors. From a total of 4067 articles, five articles met our inclusion criteria for risk factors. No studies on effectiveness of prevention programs were identified. Quality of studies included varied from fair to excellent.
Best evidence synthesis revealed moderate evidence for previous injury regardless of body location in general and fewer years of tennis experience for the occurrence of upper extremity injuries. Moderate evidence was found for lower back injuries, a previous back injury, playing >6hours/week and low lateral flexion of the neck for risk factors. Limited evidence was found for male gender as a risk factor.
The risk factors identified can assist clinicians in developing prevention-strategies. Further studies should focus on risk factor evaluation in recreational adult tennis players. 相似文献
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Jan Bourgois Albrecht L. Claessens Melissa Janssens Bart Van Renterghem Ruth Loos Martine Thomis 《Journal of sports sciences》2013,31(3):195-202
During the 1997 Federation Internationale des Societes d'Aviron (FISA) World Junior Rowing Championships, the anthropometric characteristics of 245 female junior rowers aged 17.5 ± 0.8 years (mean ± s) were assessed. Twenty-seven body dimensions (body mass, 6 heights or lengths, 4 breadths, 10 girths and 6 skinfolds) were measured in total. The elite female junior rowers were taller (174.5 ± 6.2 cm) and heavier (69.5 ± 6.2 kg), with greater length, breadth and girth dimensions, but lower skinfold thicknesses than a representative sample of Flemish (Belgian) girls of the same chronological age. An anthropometric profile chart was constructed that was rowing-specific and norms were established. Compared with scullers, sweep rowers were heavier (+4.2 kg) and taller (+2.8 cm), with greater length, breadth (except for femur width) and girth dimensions (except for calf girth). Sweep rowers also had greater skinfold thicknesses (except for the thigh and calf skinfolds). Finalists were heavier (+3.6 kg) and taller (+3.9 cm), with greater length, breadth (except for femur width) and girth dimensions (except for calf girth) than non-finalists. No significant differences were found for skinfold thicknesses between finalists and non-finalists. 相似文献
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Bart Verheyden Bert O. Eijnde Frank Beckers Luc Vanhees André E. Aubert 《Journal of sports sciences》2013,31(11):1137-1147
Abstract The purpose of this study was to evaluate the effects of a realistic, feasible, and commonly used fitness training programme on cardiac autonomic control in 14 sedentary men aged 62.0 ± 6.1 years (mean ± s). All participants performed a one-year fitness training programme in which training intensity and frequency were specifically chosen to be compliant for the majority of the participants (2 – 3 sessions per week at moderate intensity). At the same time, a reference group consisting of 15 sedentary age-matched men (age 64.2 ± 6.5 years) did not change their habitual physical activity. Measurements were performed before and after the training intervention. Cardiac autonomic control was inferred from resting values (supine and standing) of heart rate variability (HRV) computed in the frequency domain over 10-min intervals. Endurance capacity was evaluated during a maximal incremental bicycle ergometer test. In spite of an increase in peak oxygen consumption ([Vdot]O2peak) by 6.4% after training, heart rate in the training group remained unchanged at rest and at the same metabolic demand. No changes in resting parameters of HRV were shown for either groups or positions. Results from this study provide no evidence of a clinically meaningful increase in the vagal modulation to the sinus node at rest after one year of low-volume and moderate-intensity fitness training in men aged 55 – 75 years. 相似文献
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Abstract The objective of this study was to analyse the correctness of the offside judgements of the assistant referees during the final round of the FIFA 2002 World Cup. We also contrasted two hypotheses to explain the errors in judging offside. The optical error hypothesis is based on an incorrect viewing angle, while the flash-lag hypothesis refers to perceptual errors associated with the flash-lag effect (i.e. a moving object is perceived as spatially leading its real position at a discrete instant signalled by a briefly flashed stimulus). Across all 64 matches, 337 offsides were analysed using digital video technology. The error percentage was 26.2%. During the first 15 min match period, there were significantly more errors (38.5%) than during any other 15 min interval. As predicted by the flash-lag effect, we observed many more flag errors (86.6%) than non-flag errors (13.4%). Unlike the predictions of the optical error hypothesis, there was no significant difference between the correct and incorrect decisions in terms of the positioning of the assistant referees relative to the offside line (0.81 and 0.77 m ahead, respectively). To reduce the typical errors in judging offside, alternative ways need to be considered to teach assistant referees to better deal with flash-lag effects. 相似文献
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Bart Prakken 《The Information Society》2013,29(1):53-57
Our tendency is to generate ever-increasing amounts of information to deal with the uncertainties we face in today's turbulent environment. However, if we look at the problem more fundamentally, we see that uncertainty, the variable responsible for information demand, itself can be reduced. Thus, we should not get fixated on information generation (the supply-side approach) but should also consider ways of reducing needs for information flows (the demand-side approach). This article provides an overview of a Dutch sociotechnical approach that focuses on reduction of complexity so as to reduce uncertainty and thereby organizational information flows. 相似文献
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Bartłomiej Włodarczyk 《Cataloging & classification quarterly》2013,51(7):816-829
Subject searches in the National Library of Poland catalog are still comprised of a significant number of all searches, but understanding and exploration of the National Library of Poland Subject Headings causes many problems, not only for the end-users, but also for many librarians. Another problem in the National Library of Poland is the insufficient use of relationships between the terms. The solution could be a properly designed Web application based on a topic map using appropriate visualization that supports indexing and information retrieval in the National Library of Poland. The article presents the main stages of a planned project. 相似文献
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Rebels With a Cause? Adolescent Defiance From the Perspective of Reactance Theory and Self‐Determination Theory 
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下载免费PDF全文 Stijn Van Petegem Bart Soenens Maarten Vansteenkiste Wim Beyers 《Child development》2015,86(3):903-918
The present investigation focused on adolescents' defiance against parents by drawing upon psychological reactance theory (Brehm, 1966) and self‐determination theory (Ryan & Deci, 2000). Psychological reactance would be elicited when freedom is taken away, thereby motivating individuals to engage in oppositional behavior. Throughout four studies (total N = 1,472, age ranging between 12 and 21 years), it was examined whether a controlling parenting style related to adolescents' experiences of autonomy need frustration (i.e., pressure) and reactance. Reactance, in turn, would relate to more externalizing and internalizing problems. Support was obtained for these associations in community and clinical samples, making use of different informants, and controlling for responsiveness and rule setting. A vignette‐based study provided further support. The discussion highlights theoretical and clinical implications. 相似文献
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Column Editor's Note. This column focuses on formal collaboration and networking among libraries through consortia. It offers in-depth examinations of issues facing modern library consortia including (but not limited to) e-resource licensing, ebooks, next generation integrated library systems, shared print archiving, shared digital repositories, governance and other relevant topics. Contributions are accepted for this column and must be submitted to George Machovec (george@coalliance.org). Contact the column editor for suggested topics, deadlines and formatting.
ConnectNY has been involved in consortial e-book projects since 2010. Based upon the experience of these group e-book projects, we will explore different methods for assuming the shared cost of group e-book programs and then describe ways in which DDA programs may promote a positive Return on Investment (ROI) for groups as compared to individual institutions. We will argue that while use is a factor that can be taken into account when distributing cost amongst members, a budget-based percentage approach will allow consortia to effectively initiate and manage such projects over time. 相似文献