Lower limb joint kinetics during the first stance phase in athletics sprinting: three elite athlete case studies     

Neil Edward Bezodis  Aki Ilkka Tapio Salo  Grant Trewartha 《Journal of sports sciences》2013,31(8):738-746

Abstract

This study analysed the first stance phase joint kinetics of three elite sprinters to improve the understanding of technique and investigate how individual differences in technique could influence the resulting levels of performance. Force (1000 Hz) and video (200 Hz) data were collected and resultant moments, power and work at the stance leg metatarsal-phalangeal (MTP), ankle, knee and hip joints were calculated. The MTP and ankle joints both exhibited resultant plantarflexor moments throughout stance. Whilst the ankle joint generated up to four times more energy than it absorbed, the MTP joint was primarily an energy absorber. Knee extensor resultant moments and power were produced throughout the majority of stance, and the best-performing sprinter generated double and four times the amount of knee joint energy compared to the other two sprinters. The hip joint extended throughout stance. Positive hip extensor energy was generated during early stance before energy was absorbed at the hip as the resultant moment became flexor-dominant towards toe-off. The generation of energy at the ankle appears to be of greater importance than in later phases of a sprint, whilst knee joint energy generation may be vital for early acceleration and is potentially facilitated by favourable kinematics at touchdown.  相似文献   

Characteristics of the start in women's World Cup skeleton     

Nicola Bullock  David T. Martin  Angus Ross  Doug Rosemond  Terry Holland  Frank E. Marino 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(3):351-360

This study characterizes key elements of the start in elite female World Cup skeleton athletes. The top 20 female competitors in three World Cup races were videotaped within a calibrated space to allow the following components of the start to be quantified: (1) acceleration (velocity at 15-m mark, time to 15-m mark), (2) capacity (time to load, total number of steps to load), and (3) load (velocity at 45-m mark). A correlation analysis was used to establish the relationship between the variables of interest and overall start time (15- to 65-m mark). Velocity at the 15-m mark accounted for 86% of the variance in overall start time at St. Moritz and 85% at Sigulda. A stepwise regression analysis revealed that approximately 89% of the variation in start time could be explained by velocity at the 15-m mark, time to load, and velocity at the 45-m mark. Of the variables analysed in this study, rapid acceleration to attain a high velocity at the 15-m mark was the most important component of a fast overall start time. The importance of the time to load and velocity at the 45-m mark vary according to the different track characteristics.  相似文献   

Biomechanics of the ski cross start indoors on a customised training ramp and outdoors on snow     

Niels Jensby Nedergaard  Frederik Heinen  Simon Sloth  Hans-Christer Holmberg 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(3):273-286

An effective start enhances an athlete's chances of success in ski cross competitions. Accordingly, this study was designed to investigate the biomechanics of start techniques used by elite athletes and assess the influence of different start environments. Seven elite ski cross athletes performed starts indoors on a custom-built ramp; six of these also performed starts on an outdoor slope. Horizontal and vertical forces were measured by force transducers located in the handles of the start gate and a 12-camera motion capture system allowed monitoring of the sagittal knee, hip, shoulder, and elbow kinematics. The starting movement involved Pre, Pull, and Push phases. Significant differences between body sides were observed for peak vertical and resultant forces, resultant impulse, and peak angular velocity of the shoulder joint. Significantly lower peak vertical forces (44 N), higher resultant impulse (0.114 Ns/kg), and knee joint range of motion (12°) were observed indoors. Although movement in the ski cross start is generally symmetrical, asymmetric patterns of force were observed among the athletes. Two different movement strategies, i.e. pronounced hip extension or more accentuated elbow flexion, were utilised in the Pull phase. The patterns of force and movement during the indoor and outdoor starts were similar.  相似文献   

WINDOWS95的启动模式与MSDOS.SYS文件设置     

伍春晴 《嘉应学院学报》1997,15(6):70-75

本文对WINDOWS95的不同启动模式作了全面介绍,并就WINDOWS95与WINDOWS3.X的共存、如何设置MSDOS.SYS文件实现不同的启动模式,优化WINDOWS95,充分发挥计算机资源提出见解。  相似文献   

当代欧美社会运动发展的影响因素分析     

秦德占 《商丘师专学报》2007,23(11):65-69

冷战和冷战结束是二战后60多年来国际形势变动中的重大事件，对当代欧关社会运动产生了重大而深远的影响，并进而使社会运动呈现出截然不同的阶段性特征。认识和判断欧关社会运动及其未来走势，就离不开对这种国际大背景的把握，离不开对不同时期各种相关要素的分析。  相似文献   

试论人物张力在海明威作品中是如何揭示故事内核的     

买玉红 《开封教育学院学报》2007,27(1):29-30

在海明威的大部分作品中,都存在一个基本的故事内核,比如最典型的虽败犹胜的硬汉形象及人生悲剧论观点,他的这种不同程度的重复,通过作品中人物之间的关系展现出来。从他的几部作品中的人物张力入手,可以揭示其是如何通过人物张力来展示故事内核的。  相似文献   

冷战前期的美国高等教育政治化初探     

於荣 《教育与考试》2007,(1)

冷战前期,美国高等教育成为美国政府用于冷战的工具,高等教育具有明显的政治化特征。美国高等教育的政治化是建立在工具主义哲学、美国宪法所规定的“弹性条款”和美国成为帝国主义强国等基础之上的。美国高等教育的政治化在自然科学研究、社会科学研究、高等教育民主化和教育输出等方面表现尤为突出。美国高等教育政治化反映了高等教育为美国国家利益服务的实质。  相似文献   

“大跃进”运动开始时间新论   总被引：4，自引：0，他引：4  

王治涛 《河南师范大学学报(哲学社会科学版)》2004,31(6):95-99

“大跃进”运动开始或“正式”开始于1958年5月的中共八大二次会议,这是目前史学界通行的看法。其实,“大跃进”运动开始于1957年10月。“大跃进”运动是作为“社会主义建设总路线”的产物出现的,作为“总路线”中心的“多快好省”是在1955年下半年就完全出现并很快响遍全国和贯彻到实际工作中的;作为“大跃进”运动开路方法的大辩论在1957年10月前后已被肯定并广泛使用开来,这就使得发动及进行“大跃进”运动有了有利条件;中共中央和毛泽东批评“反冒进”的过程,也就是号召、部署“大跃进”运动的过程。中共中央在1957年10月前后,更是对“大跃进”运动做出了明确的部署;从1957年冬农业方面投入水利建设和积肥运动的劳动力情况看,是“大跃进”运动中常用的“大兵团作战”组织形式;1957年10月后迅速出现的农业“大跃进”运动,有力地推动了工业“大跃进”局面的迅速形成。农业、工业战线的“大跃进”运动,又推动了交通运输、商业等经济战线及文教卫生等战线迅速形成“大跃进”局面;1957年10月中共八届三中到1958年5月中共八大二次会议间工业战线和其他战线取得的成绩情况看,1957年10月后已是“大跃进”的局面了。  相似文献   

冷战期间东盟国家与中国关系回眸     

张连福 《巢湖学院学报》2007,9(5):6-11

冷战期间,受两极对抗格局、东南亚地区形势及多种双边因素的影响和制约,东盟国家与中国的关系经历了从敌视对抗到缓和合作的曲折历程。本文试对这一时期双方关系进行较为全面系统的回顾梳理,并对影响双方关系的相关因素作一简要分析。  相似文献   

后冷战时期美国对华政策中的两党政治因素分析     

陈旭 《湖州师范学院学报》2007,29(3):65-67

与西方其他国家的政党制度相比,历史上美国两党制度形成了一些能够影响其政策制定的突出特点。冷战后国际环境出现了新变化,美国将中国视为“潜在对手”,主张遏制中国。适应这一主流舆论,在具体操作层面,两党政治起到了推波助澜的作用。在两党政治下,对华政策往往被两党当作争取各种利益的一张“牌”来利用,从而不可避免地影响到美国的对华外交。  相似文献