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   

浅谈计算机辅助数学教学的优越性     

李美蓉 《安徽教育学院学报》2005,23(3):15-16

随着计算机在校园的广泛应用,计算机辅助教学已经受到社会各界的普遍关注,本文从六个方面阐述了计算机辅助数学教学的优越性.  相似文献   

对高等数学课程及教学改革的思考     

侯宗毅 《河池学院学报》2003,23(2):46-48

针对目前高等数学课程教学中存在的主要问题 ,结合教学实际 ,对高等数学在教学观念、教学方法、教学模式、教学内容及教材建设等方面提出一些改革措施和意见  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   

略论激发学生学习数学的兴趣     

罗玉昆 《铜仁学院学报》2005,7(8):68-69,83

兴趣是最好的老师。为引导学生对学习数学产生兴趣，教师应创设情境，诱发学生的学习兴趣；运用直观教学，培养学生的学习兴趣；引导学生动手操作，激发学生的学习兴趣；多用鼓励性语言，调动学生的学习兴趣。  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   

建构主义与数学教学     

姚敏 《沈阳教育学院学报》2003,5(3):108-109

随着社会对人才数学修养的要求不断提高，传统数学教学的弊端日益显现出来，建构主义学习理论的许多观点和主张具有合理性，对数学教学的改革有借鉴意义。  相似文献   

让学生学会做数学——课改下的数学教学新理念     

刘晓成 《潍坊教育学院学报》2006,19(3):59-61

新课标要求数学教学要让学生学会“做数学”,做数学”的目的最终是要让学生学会“数学化”。“做数学”的实质是把重点从“教”转向“学”,从教师的行为转向学生的活动,并且从感觉效应转向活动效应,使学生在数学的活动中感知数学、认识数学、体验数学和应用数学。  相似文献