现代三级跳远的最佳三跳比例的探讨

本文以具有当今世界水平的三级跳远选手的30组测试成绩为依据,运用二次响应面回归模型,研究了三级跳远成绩与三跳远度的关系。并用冷嵴分析的方法,给出了使三级跳远成绩达到最大值的最佳三跳组合(比例)模式。     

The effects of vibration on explosive and reactive strength when applying individualized vibration frequencies

Abstract

The aim of this study was to assess the effects of 8 weeks of whole-body vibrations on explosive and reactive leg strength. Thirty-three physically active students took part in the study and were randomly assigned to an individualized-vibration group, a fixed-vibration group or a control group. The frequency of vibration was set to 30 Hz for the fixed-vibration group, whereas the frequency for the individualized-vibration group was determined by monitoring the participants' EMG_rms activity. The participants in the two vibration groups were exposed three times a week for 8 weeks to a series of 10 × 1-min whole-body vibrations with a 1-min pause between series of vibrations and a 4-min pause after the first five series of vibrations. Jump height in the squat jump increased significantly in all three groups (by 11% for the individualized-vibration group, p = 0.001; by 3% for the fixed-vibration group, p = 0.011; and by 2% for the control group, p = 0.006), but countermovement jump height was not affected. In continuous rebound jumps by the individualized-vibration group, jumping height increased by 22% (p = 0.006) and power increased by 18% (p = 0.002). The results of this study suggest that the use of an individualized vibration frequency produces a greater response from the neuromuscular system and is more beneficial than vibrations at a fixed pre-selected frequency.     

Explosive force production during isometric squats correlates with athletic performance in rugby union players

Abstract

This study investigated the association between explosive force production during isometric squats and athletic performance (sprint time and countermovement jump height). Sprint time (5 and 20 m) and jump height were recorded in 18 male elite-standard varsity rugby union players. Participants also completed a series of maximal- and explosive-isometric squats to measure maximal force and explosive force at 50-ms intervals up to 250 ms from force onset. Sprint performance was related to early phase (≤100 ms) explosive force normalised to maximal force (5 m, r = ?0.63, P = 0.005; and 20 m, r = ?0.54, P = 0.020), but jump height was related to later phase (>100 ms) absolute explosive force (0.51 < r < 0.61; 0.006 < P < 0.035). When participants were separated for 5-m sprint time (< or ≥ 1s), the faster group had greater normalised explosive force in the first 150 ms of explosive-isometric squats (33–67%; 0.001 < P < 0.017). The results suggest that explosive force production during isometric squats was associated with athletic performance. Specifically, sprint performance was most strongly related to the proportion of maximal force achieved in the initial phase of explosive-isometric squats, whilst jump height was most strongly related to absolute force in the later phase of the explosive-isometric squats.     

Implementing technical refinement in high-level athletics: exploring the knowledge schemas of coaches

This paper explores the approaches adopted by high-level field athletics coaches when attempting to refine an athlete’s already well-established technique (long and triple jump and javelin throwing). Six coaches, who had all coached multiple athletes to multiple major championships, took part in semi-structured interviews focused upon a recent example of technique refinement. Data were analysed using a thematic content analysis. The coaching tools reported were generally consistent with those advised by the existing literature, focusing on attaining “buy-in”, utilising part-practice, restoring movement automaticity and securing performance under pressure. Five of the six coaches reported using a systematic sequence of stages to implement the refinement, although the number and content of these stages varied between them. Notably, however, there were no formal sources of knowledge (e.g., coach education or training) provided to inform coaches’ decision making. Instead, coaches’ decisions were largely based on experience both within and outside the sporting domain. Data offer a useful stimulus for reflection amongst sport practitioners confronted by the problem of technique refinement. Certainly the limited awareness of existing guidelines on technique refinement expressed by the coaches emphasises a need for further collaborative work by researchers and coach educators to disseminate best practice.     

基于外汇汇率买入的带跳扩散股票的期权定价

在风险中性假设下,通过建立以外币计价的股票价格服从带跳扩散过程的随机微分方程和外币汇率的随机微分方程,考虑到影响外汇汇率的因素和影响股票价格因素的相关性,得到了与之相关联的买入的以本币计价的欧式期权定价公式．     

The Effect of Depth Jumps and Weight Training on Leg Strength and Vertical Jump

Abstract

In recent years, a method of plyometrics (exercises that cause a rapid lengthening of a muscle prior to contraction) called depth jumping has become a part of the training routine of many athletes. Two experiments are described in which the effectiveness of the exercises is examined. In Experiment 1, undergraduate students in beginning weight training classes trained with three different jumping programs: (1) maximum vertical jumps, (2) 0.3 m depth jumps, and (3) 0.75 m and 1.10 m depth jumps. In addition, all groups also lifted weights. In Experiment 2, a weight training class and the volleyball team at Brigham Young University-Hawaii were divided into two groups. One group lifted weights and performed 0.75 and 1.10 m depth jumps. The other group only lifted weights. In Experiment 1, the three training programs resulted in increases in one repetition maximum (1 RM) squat strength, isometric knee extension strength, and in vertical jump; however, there were no significant differences between treatments. In Experiment 2, all groups made significant increases in vertical jump, except the group of weight lifters, who did no jumping. It was concluded that depth jumps are effective but not more effective than a regular jumping routine.     

基于遗传算法的低功耗芯片BIST确定测试

针对芯片内建自测试的功耗问题,通过优化测试向量排序来实现低功耗测试。采用遗传演化思想,从减少被测电路内部节点电平翻转和自动测试向量生成电路的电平翻转两方面实现目标优化,并设计了相应的测试向量编码、目标函数、适应度函数、遗传算子和遗传算法。通过对ISCAS85和IS-CAS89基准电路的仿真测试结果证明,本文的方法比目前典型的低功耗测试方法在电平翻转数上减少了10%~33%,从而能够进一步降低测试功耗。     

女子田径跳跃项群发展态势的比较研究

通过文献资料、数理统计、比较等研究方法,对世界23~28届奥运会、中国5~9届全运会及中国2004年全国田径大奖赛总决赛女子田径跳跃项群前8名成绩进行统计分析。结果表明,世界女子田径跳跃项群呈现多极格局,俄罗斯在跳高项目上具有绝对实力;世界女子田径跳跃项群4个项目呈上升发展趋势,且成绩表现出较稳定。中国在跳高和跳远两个项目上整体发展速度较快,但逐期增长速度较低;在三级跳远和撑杆跳高两项上,中国出现负增长,特别是撑杆跳高下滑最严重。     

我国优秀男子跳远运动员起跳技术的运动学分析

通过运用献资料法、统计法、比较分析法等研究方法，对我国的11名优秀男子跳远运动员和国外6名优秀跳远运动员在起跳阶段有关的运动学参数进行比较分析，结果表明我国优秀运动员助跑速度低，腾起垂直速度小，腾起角度偏小。“跑不快，跳不起”仍是我国跳远运动员的共性。运动员助跑的绝对速度能力低，起跳腿的专项力量素质差，是制约我国跳远运动员跳远成绩进一步提高的关键因素。     

三级跳远运动员的训练负荷量分析及关键性训练因素研究

对三级跳远运动员的训练负荷量分析及关键性训练因素进行剖析 ,不同级的运动员的训练负荷量的结构中 ,一般训练负荷量和发展性负荷量在所占的比重存在不同的比例。关键性训练因素对三级跳远运动员成绩所起的作用有训练负荷因素、身体机能因素、教练因素占有主导作用