Biomechanics of aggressive inline skating: landing and balancing on a grind rail     

Major MJ  Beaudoin AJ  Kurath P  Hsiao-Wecksler ET 《Journal of sports sciences》2007,25(12):1411-1422

Currently, only epidemiological injury data have been reported for the new extreme sport of aggressive inline skating, or trick skating. No studies have examined the biomechanics of this sport, which involves repetitive jumping and landing from railings, ramps, and ledges, often over 1 m in height. We present results of a pilot study that examined the effect of skater experience and lower extremity biomechanics on energy absorption ability, and observed balance strategies used during two basic tricks. In these tricks, the skater jumps onto an elevated rail and maintains balance while standing in a single position (stall) or sliding along the rail (grind). Lower extremity joint kinematics, impact force characteristics, and general movement behaviours were examined during landing and balance phases. Ten male skaters performed ten stalls and ten frontside grinds on an instrumented grind rail, capable of measuring vertical force. Vertical impact force was found to decrease with increasing skater experience in stalls (r = -0.84, P = 0.002) and grinds (r = -0.84, P = 0.009). This might imply that less-experienced skaters are (subconsciously) more concerned about maintaining balance than refining technique to minimize impact force. Similar to drop landing experiments, peak impact force decreased with increasing knee flexion during stalls (r = -0.65, P = 0.04). During stalls, skaters demonstrated classic balance maintenance strategies (ankle, hip, or multi-joint) depending on trick length. During grinds, skater centre of mass never passed over the rail base of support, suggesting the use of momentum produced from obliquely approaching the rail.  相似文献   

Helsen, Gilis and Weston (2006) err in testing the optical error hypothesis     

Oudejans RR  Bakker FC  Beek PJ 《Journal of sports sciences》2007,25(9):987-990

In this commentary, we react to the recent study by Helsen, Gilis and Weston (2006) on judging offside in football. Helsen et al. claim that their data falsify the optical error hypothesis presented by Oudejans et al. (2000). However, as we will elucidate here, they misinterpret this hypothesis and present a data set that is seriously flawed, and hence not suited to test it. Therefore, their conclusions regarding the optical error hypothesis are in error.  相似文献   

Elite football on artificial turf versus natural grass: movement patterns, technical standards, and player impressions     

Andersson H  Ekblom B  Krustrup P 《Journal of sports sciences》2008,26(2):113-122

The aim of the present study was to examine the movement patterns, ball skills, and the impressions of Swedish elite football players during competitive games on artificial turf and natural grass. Time - motion analyses (36 observations) and technical analyses (16 team observations) were performed and 72 male and 21 female players completed a questionnaire. No differences were observed between artificial turf and natural grass in terms of total distance covered (mean 10.19 km, s = 0.19 vs. 10.33 km, s = 0.23), high-intensity running (1.86 km, s = 0.10 vs. 1.87 km, s = 0.14), number of sprints (21, s = 1 vs. 22, s = 2), standing tackles (10, s = 1 vs. 11, s = 1) or headers per game (8, s = 1 vs. 8, s = 1), whereas there were fewer sliding tackles (P < 0.05) on artificial turf than natural grass (2.1, s = 0.5 vs. 4.3, s = 0.6). There were more short passes (218, s = 14 vs. 167, s = 12) and midfield-to-midfield passes (148, s = 11 vs. 107, s = 8) (both P < 0.05) on artificial turf than natural grass. On a scale of 0-10, where 0 = "better than", 5 = "equal to", and 10 = "worse than", the male players reported a negative overall impression (8.3, s = 0.2), poorer ball control (7.3, s = 0.3), and greater physical effort (7.2, s = 0.2) on artificial turf than natural grass. In conclusion, the running activities and technical standard were similar during games on artificial turf and natural grass. However, fewer sliding tackles and more short passes were performed during games on artificial turf. The observed change in playing style could partly explain the male players' negative impression of artificial turf.  相似文献   

Report to the directors of the London and Birmingham Railway Company,accompanied by experiments on the transverse strength, &c. of malleable iron,with reference to its use for railway bars     

Peter Barlow 《Journal of The Franklin Institute》1835,20(2):118-127

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Report to the directors of the London and Birmingham Railway Company,accompanied by experiments on the transverse strength, &c. of malleable iron,with reference to its use for railway bars     

Peter Barlow 《Journal of The Franklin Institute》1835,20(3):188-194

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International: Developing a multinational training model for management     

Peter Geib  George R. McMeen 《Performance Improvement》1988,27(4):23-26

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Assessment of mentally retarded children with the Matrix Analogies Test-Short Form,Draw A Person: A quantitative scoring system,and the Kaufman Test of Educational Achievement     

Peter N. Prewett  Achilles N. Bardos  Jack A. Naglieri 《Psychology in the schools》1989,26(3):254-260

This study examined the utility of the MAT-SF and the DAP: A Quantitative Scoring System as screening instruments for mental retardation. In this study, 46 normals and 39 developmentally handicapped (DH) 4th- and 5th-grade students were group administered both screening tests and individually administered an achievement test, the KTEA. The results found the MAT-SF to correlate significantly with all areas of achievement for both groups, whereas the DAP did not correlate significantly with any areas of achievement for the normal group but correlated significantly with math, but not reading, for the developmentally handicapped students. The results support the use of the MAT-SF as a screening instrument for mental retardation, whereas the usefulness of the DAP is not as clear.  相似文献   

Humility & Humiliation: The Transformation of Franciscan Humour,c.1210–1310     

Peter J. A. Jones 《Cultural and Social History》2018,15(2):155-175

Humiliation and self-ridicule worked as surprisingly important tools of evangelical outreach in the first decades of the Franciscan Order (c.1210–50). According to early Franciscan texts such as the Assisi Compilation (c.1240s) and Jordan of Giano’s Chronica (c.1260), St Francis and his earliest followers sought to win supporters by stripping naked in public, mocking learned preachers and ludicrously imitating animals. Yet within a few decades of the founder’s death this type of humour had been erased from Franciscan texts. Chronicles now omitted references to Francis’s laughter, while humiliating behaviour came to be condemned by Franciscan preachers, chroniclers and theologians alike. From being a means of undermining dignity and reason, joking was now instead celebrated as a tool of upholding these very same values. Describing the nature of this shift, and contextualising it within the evolving institutional priorities of the Franciscans under the leadership of Bonaventure (d.1274), this article will complicate debates about the development of medieval humour, while also reflecting on laughter’s role as a means of resistance to the significant social and cultural upheavals of the 1200s.  相似文献   

Excellence and Frontier Research as Travelling Concepts in Science Policymaking     

Tim Flink  Tobias Peter 《Minerva》2018,56(4):431-452

Excellence and frontier research have made inroads into European research policymaking and structure political agendas, funding programs and evaluation practices. The two concepts travelled a long way from the United States and have derived from contexts outside of science (and policy). Following their conceptual journey, we ask how excellence and frontier research have percolated into European science and higher education policies and how they have turned into lubricants of competition that buttress an ongoing reform process in Europe.  相似文献   

Football Club Formation and the Lancashire Leisure Class, 1857–1870     

Peter Swain 《国际体育史杂志》2017,34(7-8):498-516

This paper outlines the transition from football games played for occasional amusement to a system of organized football clubs playing regular matches in Lancashire in the mid-nineteenth century. This was led by young men of an emerging Lancashire leisured class being, in the main, the public school educated sons of the northern county’s commercial and industrial elite. These families had accumulated sufficient wealth, especially in the first half of the nineteenth century, to exempt a considerable part of their population from work both at weekends and during the normal working week with football becoming an act of conspicuous consumption. Three case studies of individual clubs and leading individuals within those clubs are presented with detailed archival research carefully avoiding the teleology implicit in much historical writing of the past. It also swells the paucity of good historical material about the organization of sport at levels below national bodies. In so doing, it aims to illuminate some of the shadows in the big picture of the evolution of sport and leisure in Lancashire and Britain itself while informing the ongoing orthodox/revisionist debate into the origins of football in the nineteenth century.  相似文献