The influence of Cardan rotation sequence on angular orientation data for the lower limb in the soccer kick

Abstract

The influence of the Cardan rotation sequence on the orientation angles for joints is well known but has not been explored for dynamic sports movements. The purpose of this study is to establish the influence of Cardan rotation sequence on the orientation angles of the ankle, knee, and hip of the support leg and pelvis during dynamic sports movements, typified by a maximal instep kick in soccer. We found that: (a) the X (flexion/extension) axis rotations provide data that are robust for any sequence used other than the YXZ sequence, although the Y (abduction/adduction) and Z (internal/external) axes rotations are variable in both shape and offset magnitude; (b) the preferred rotation sequence is either XYZ or XZY for dynamic sports movements, although for the soccer kick the XYZ rotation sequence has been widely used and so this is recommended as a standard; and (c) most uncertainties exist in the Y and Z axes and are most apparent at the beginning of the movement. Where uncertainty exists in identifying Y and Z axes orientations, the integrated angular velocity may be considered as an alternative to determine the relative changes in segment orientation.     

现代竞技足球比赛中点球判罚的影响因素分析

采用文献资料法、观察统计法、数理统计法及访谈法,对第19届世界杯足球赛决赛阶段点球判罚情况进行统计研究,对比赛中影响点球判罚的相关因素进行分析。结果表明,规则、裁判等因素对比赛中点球的判罚具有影响作用,对这些因素进行客观分析,为现代竞技足球比赛中点球的判罚提供参考和依据。     

Tennis

This study investigated the effect of the larger diameter (Type 3) tennis ball on performance and muscle activation in the serve. Sixteen male advanced tennis players performed serves using regular size and Type 3 tennis balls. Ball speed, surface electromyography, and serve accuracy were measured. There were no significant differences in mean initial serve speeds between balls, but accuracy was significantly greater (19.3%) with the Type 3 ball than with the regular ball. A consistent temporal sequence of muscle activation and significant differences in mean activation of different muscles were observed. However, ball type had no effect on mean arm muscle activation. These data, combined with a previous study, suggest that play with the larger ball is not likely to increase the risk of overuse injury, but serving accuracy may increase compared to play with the regular ball.     

人性中的"蝴蝶"与"甲壳虫"——评《吉姆爷》中的象征

康拉德的长篇小说《吉姆爷》集中体现他的艺术追求和道德探索;它的一大特色是象征性。小说中最令人回味的是"蝴蝶"与"甲壳虫"的象征意义,它们象征着人性的双重性,吉姆这个典型人的人性的双重性。     

散打运动员侧踹腿力学特征的研究

应用KISTLER三维测力平台对散打一级运动员及健将级运动员优势与弱势侧踹腿动作力量和时间进行测试。结果表明：一级运动员优势侧踹腿和弱势侧踹腿在力量上存在显著差异,与健将级运动员相比,力量与时间都存在显著性差异,说明侧踹腿的动作力量对竞技水平提高有一定的影响,建议教练员加强运动员侧踹腿力量训练,特别针对弱势腿训练。为散打教练员提供侧踹腿技术教学和训练的科学化、规范化、系统化,提供定量的数据和理论参考。     

欧洲杯足球前场任意球进攻特点的探讨

在足球比赛中,前场任意球进攻有着不可估量的价值。它有时可以直接破门得分,有时可以通过队员之间的配合,巧妙地破门,进攻队员在距离防守队员9.15m之间可以从容起脚,而且有充裕的时间。在第十届欧洲杯大赛中,有一些前场任意球进攻很有特色,给观众留下了深刻的印象。现根据本届杯赛的部分电视录像镜头,分析本届杯赛前场任意球的进攻特点,对这些有特色的战术进行总结,望能够给国内任意球战术带来借鉴。     

跆拳道后旋踢技术动作的运动学特征分析

采用三维高速摄像技术和运动生物力学原理,对后旋踢技术身体重心移动、动作所用时间、踝关节角度、膝关节角度和髋关节角度的运动学特征进行比较分析,得出结论:踢击腿在离地瞬间身体重心要快速向回旋方向移动;踢击腿膝关节最大程度弯曲,以缩短动作时间、加快踢击速度;踢击腿髋关节只有最大程度地弯曲,弯曲的膝关节才能快速展开;踢击腿的髋关节最大程度弯曲再打开时,踝关节能快速鞭打;支撑腿弯曲后在踢击腿踢出的瞬间,髋关节开始伸展,将对打击高度产生影响;踢击腿膝关节和髋关节最大程度弯曲时能增加击打力度.     

蝴蝶不同部位提取DNA效果的研究

提取高质量的蝴蝶基因组是蝶类分子系统学研究的重要步骤。本文通过对蝴蝶干标本不同部位DNA提取效果的比较,找出了最适合蝴蝶干标本基因组DNA提取的部位,同时用PCR扩增的方法进行了检验,力争为开展蝴蝶的分子生物学研究奠定基础。结果表明,足部的提取效果最佳。     

毽球倒勾球技术教学球感练习法研究

依据毽球倒勾球动作技术的时间与空间特征,结合教学实践经验,运用运动心理学有关球感的理论,在分析与探讨球感练习对毽球倒勾球动作技能形成的作用的基础上,对毽球倒勾球动作技术教学中球感练习选择的依据、练习顺序、练习手段及基本要求、运用球感练习的基本原则等问题进行了分析与讨论。     

“诗”“歌”中蝴蝶意象研究

蝴蝶是诗词中常见的一种意象,多用来表达自由闲适、爱情新生、美丽感伤等主题。文章探讨古典诗词中的蝴蝶意象,通过对蝴蝶意象的阐释来把握诗人对世界独特的理解,以及特定时代诗歌的某种整体经验。