Ground reaction forces of Olympic and World Championship race walkers     

Brian Hanley  Athanassios Bissas 《European Journal of Sport Science》2016,16(1):50-56

Race walking is an Olympic event where no visible loss of contact should occur and the knee must be straightened until midstance. The purpose of this study was to analyse ground reaction forces of world-class race walkers and associate them with key spatiotemporal variables. Nineteen athletes race walked along an indoor track and made contact with two force plates (1000 Hz) while being filmed using high-speed videography (100 Hz). Race walking speed was correlated with flight time (r = .46, p = .049) and flight distance (r = .69, p = .001). The knee's movement from hyperextension to flexion during late stance meant the vertical push-off force that followed midstance was smaller than the earlier loading peak (p < .001), resulting in a flattened profile. Athletes with narrower stride widths experienced reduced peak braking forces (r = .49, p = .046), peak propulsive forces (r = .54, p = .027), peak medial forces (r = .63, p = .007) and peak vertical push-off forces (r = .60, p = .011). Lower fluctuations in speed during stance were associated with higher stride frequencies (r = .69, p = .001), and highlighted the importance of avoiding too much braking in early stance. The flattened trajectory and consequential decrease in vertical propulsion might help the race walker avoid visible loss of contact (although non-visible flight times were useful in increasing stride length), while a narrow stride width was important in reducing peak forces in all three directions and could improve movement efficiency.  相似文献   

Talent identification and selection in elite youth football: An Australian context     

Donna O'Connor  Paul Larkin  A. Mark Williams 《European Journal of Sport Science》2016,16(7):837-844

We identified the perceptual–cognitive skills and player history variables that differentiate players selected or not selected into an elite youth football (i.e. soccer) programme in Australia. A sample of elite youth male football players (n?=?127) completed an adapted participation history questionnaire and video-based assessments of perceptual–cognitive skills. Following data collection, 22 of these players were offered a full-time scholarship for enrolment at an elite player residential programme. Participants selected for the scholarship programme recorded superior performance on the combined perceptual–cognitive skills tests compared to the non-selected group. There were no significant between group differences on the player history variables. Stepwise discriminant function analysis identified four predictor variables that resulted in the best categorization of selected and non-selected players (i.e. recent match-play performance, region, number of other sports participated, combined perceptual–cognitive performance). The effectiveness of the discriminant function is reflected by 93.7% of players being correctly classified, with the four variables accounting for 57.6% of the variance. Our discriminating model for selection may provide a greater understanding of the factors that influence elite youth talent selection and identification.  相似文献   

Effects of load mass carried in a backpack upon respiratory muscle fatigue     

Mark Faghy  Sam Blacker  Peter I. Brown 《European Journal of Sport Science》2016,16(8):1032-1038

Purpose: The purpose of this study was to investigate whether loads carried in a backpack, with a load mass ranging from 0 to 20?kg, causes respiratory muscle fatigue. Methods: Eight males performed four randomised load carriage (LC) trials comprising 60?min walking at 6.5?km?h^?1 wearing a backpack of either 0 (LC₀), 10 (LC₁₀), 15 (LC₁₅) or 20?kg (LC₂₀). Inspiratory (P_Imax) and expiratory (P_Emax) mouth pressures were assessed prior to and immediately following each trial. Pulmonary gas exchange, heart rate (HR), blood lactate and glucose concentration and perceptual responses were recorded during the first and final 60?s of each trial. Results: Group mean P_Imax and P_Emax were unchanged following 60-min load carriage in all conditions (p?>?.05). There was an increase over time in pulmonary gas exchange, HR and perceptions of effort relative to baseline measures during each trial (p?p?>?.05). Conclusions: These findings indicate that sub-maximal walking with no load or carrying 10, 15 or 20?kg in a backpack for up to 60?min does not cause respiratory muscle fatigue despite causing an increase in physiological, metabolic and perceptual parameters.  相似文献   

绩效和财富：我国公司治理中的股价效应     

阳晓明 《四川师范大学学报(社会科学版)》2003,30(1):14-19

资本市场是公司外部治理机制的主导力量。股份水平既是管理绩效的显示，又具有巨大的财富效应。低估的股价可能引发代理权竞争和敌意接管。在我国，股价在公司治理中的约束机制和激励机制失效，其原因除了证券市场上股价形成机制的非理性因素外，更主要的原因在于我国公司治理结构中的先天性缺陷，其中关键是要解决公司股权结构中的国有股“一股独大”的问题。  相似文献   

农村合作经济组织增进融资绩效的机制分析     

张崭  秘娜 《高校教育管理》2005,(4)

传统农村金融安排由于其制度上存在缺陷,不能有效地满足广大农户的金融需求,农村金融资源流失严重。农村合作经济组织是伴随农业产业结构调整而衍生出来的一种中介组织。当其以中间变量的形式存在于农村金融组织与农户之间后,便可以通过其组织职能、载体职能及中介与服务职能派生出多种机制来有效地降低农村金融交易费用,增进农户融资绩效。  相似文献   

从课文教学中培养英语语感     

杜鸣  曲小梅 《岱宗学刊(泰安教育学院学报)》2001,(3)

学习英语的最终目的是进行交际 ,语感与语言运用能力紧密相关 ,语感是外语课文教学的关键。本文从对课文整体教学角度来阐述如何培养学生的英语语感  相似文献   

Different Disciplines Require Different Motivations for Student Success     

Rosanna Breen  Roger Lindsay 《Research in higher education》2002,43(6):693-725

This article reports an investigation of undergraduate motivation to learn. A Likert-type rating scale measure of motivation incorporated the general motivational dimensions identified by previous investigators, as well as a systematic theoretical framework that is more novel, and attempts to acknowledge the role of discipline-specific factors in motivation to learn. The motivation questionnaire was evaluated by measuring its success in explaining the academic achievement of biology, history, computing, planning, anthropology, geology, food science and nutrition, and education students (n = 380) in standard university assessments. The findings reveal that student performance is better explained by within- than across-discipline indexes of motivation, probably because some types of motivation lead to success in some disciplines but failure in others. Furthermore, items based on the theoretical framework developed to underpin the questionnaire (which distinguishes outcome from process incentives) were also found to explain more variation in student performance than general motivation items. Some practical implications of the findings are considered.  相似文献   

高职学生绩效管理的实证研究     

盖庆武  汪涛  潘毅  王春柳  黄爱素 《浙江工贸职业技术学院学报》2006,6(4):84-88

将绩效管理理论运用于高职学生管理中，采用现场研究方法设置试验组（45人）和控制组（71人），对试验组进行学生绩效管理控制。一个学期后考察学生德育、智育、体育和综合能力考评情况。试验结果表明在学生管理中采取绩效管理的思想与方法，可以显著提高学生绩效。  相似文献   

Factors affecting the career progress of academic accountants in Australia: Cross-institutional and gender perspectives     

Nava Subramaniam 《Higher Education》2003,46(4):507-542

Since the late 1980s, Australian highereducation has undergone significant reforms andpolicy changes based on economic rationalismand modernisation of management. This paperexamines the outcomes of the reform processesbased on the career attributes, status andperceptions of work environment of academicaccountants in Australian universities.Similarities and differences between academicaccountants are explored fromcross-institutional and gender perspectives.The data provide insight into a number ofsystemic inequalities between the older andmore established universities and the neweruniversities. In specific, across-institutional analysis based on fouruniversity types: Sandstones/Redbricks,Gumtrees, Unitechs and New (Marginson 1999)indicates that academic accountants in Newuniversities employ a much lower proportion ofstaff with PhD qualification, a weakerpublication profile, and perceive greaterbarriers for conducting research in terms of ashortage of research mentors, colleagues withresearch experience, and post-graduatestudents. Further, the commitment to flexiblelearning and delivery strategies iscomparatively stronger in Unitechs, and posesadditional demands on accounting academics'overall workload. Perceptions of gender-baseddiscrimination by female academic accountantsare generally stronger than their malecounterparts, particularly, in Newuniversities. These results raise severalissues for academic accountants at both theinstitutional and individual level in terms ofequal employment opportunities, management ofresearch programmes, development of teachingstrategies and individual time management.  相似文献   

外界条件对溴冷机性能影响的研究     

朱章竞  朱建华 《茂名学院学报》2001,11(4):56-59

溴化锂吸收式制冷机的性能，通常指运行时所产生的冷量及与之相关的热力系数，蒸汽单耗等技术经济指标而言，分析影响溴冷机性能的各种因素，研究提高溴冷机性能，延长使用寿命的方案。  相似文献