Comparing the magnitude and direction of asymmetry during the squat,countermovement and drop jump tests in elite youth female soccer players

ABSTRACT

The aims of the present study were to provide an in-depth comparison of inter-limb asymmetry and determine how consistently asymmetry favours the same limb during different vertical jump tests. Eighteen elite female under-17 soccer players conducted unilateral squat jumps (SJ), countermovement jumps (CMJ) and drop jumps (DJ) on a portable force platform, with jump height, peak force, concentric impulse and peak power as common metrics across tests. For the magnitude of asymmetry, concentric impulse was significantly greater during the SJ test compared to CMJ (p = 0.019) and DJ (p = 0.003). No other significant differences in magnitude were present. For the direction of asymmetry, Kappa coefficients revealed fair to substantial levels of agreement between the SJ and CMJ (Kappa = 0.35 to 0.61) tests, but only slight to fair levels of agreement between the SJ and DJ (Kappa = ?0.26 to 0.18) and CMJ and DJ (Kappa = ?0.13 to 0.26) tests. These results highlight that the mean asymmetry value may be a poor indicator of true variability of between-limb differences in healthy athletes. The direction of asymmetry may provide a useful monitoring tool for practitioners in healthy athletes, when no obvious between-limb deficit exists.     

Components of Variance of Scales With a Bifactor Subscale Structure From Two Calculations of α

Since Cronbach's (1951) elaboration of α from its introduction by Guttman (1945), this coefficient has become ubiquitous in characterizing assessment instruments in education, psychology, and other social sciences. Also ubiquitous are caveats on the calculation and interpretation of this coefficient. This article summarizes a recent contribution (Andrich, 2015) on the use of coefficient α which complements these many caveats. It shows that in the presence of a simple bifactor structure of a scale where unique components of variance are homogeneous in magnitude, three components of variance and the common latent common correlation among the subscales can be calculated from the ratio of two calculations of α, one at the level of the items, the other at the level of the subscales. It was suggested that these two ready calculations and their interpretation, and the reporting of all four indices in the analysis of scales with a subscale structure, would reduce the misinterpretation of this coefficient. An illustrative example of the application of the calculations is also shown.     

运算放大器工作状态的判断及分析

在电子技术教学中,分析运算放大器系统时,应根据运算放大器系统的反馈情况,判断它的工作状态;分析工作状态时,要充分考虑运放系统是处于线性区还是饱和区。线性区可按虚短或虚地原则处理,饱和时不能按虚短原则处理,应用“虚短”和“虚地”时应注意“虚短”是“虚地”的特殊形式。     

酒精体胀系数的测量方法

利用酒精温度计法测定玻璃体内酒精的体胀系数。     

影响大学生篮球裁判员临场判罚的因素与对策研究

主要采用文献资料法、访谈法、观察法,对影响我校篮球裁判临场判罚的因素进行了以下具体的分析认为:在篮球比赛中裁判临场判罚时容易出现的问题是理论知识不熟、临场实践少、基本功不扎实、临场心理因素不稳定、体能欠缺、思想因素等方面有关系,解决问题的关键是加强我校篮球裁判对篮球规则和裁判法的理解,通过不断的实践,逐步提高自身的执裁水平;通过学习理论然后结合实践,不断积累临场经验,通过参执裁不同层次比赛的,在实践中不断增强自身的执裁能力,增强自信心;加强心理素质的培养和身体素质的锻炼。     

用稳态近似法推导反应速度方程时应注意的一个问题

用稳态近似法推导反应的速度方程时,最后所导出的速度方程有时会出现由不不同数值而组成的系数。针对这个问题,本文指出了两种避免出现该问题的方法。     

Digital speckle pattern interferometric measurement of diffusioncoefficients in hydrogels

ＩＮＴＲＯＤＵＣＴＩＯＮＴｈｅｒａｔｅｏｆｄｉｆｆｕｓｉｏｎｏｆｓｕｒｆａｃｔａｎｔｓｉｎｇｅｌｓｉｓａｎｉｍｐｏｒｔａｎｔｐｒｏｐｅｒｔｙｂｏｔｈｆｏｒｔｈｅｃｈａｒａｃｔｅｒｉｚａ ｔｉｏｎｏｆｓｏｌｕｔｅ ｇｅｌｉｎｔｅｒａｃｔｉｏｎｓａｎｄｆｏｒｔｈｅｄｅｓｉｇｎｏｆｎｏｖｅｌａｐｐｌｉｃａｔｉｏｎｓｏｆｓｕｃｈｍａｔｅｒｉａｌｓ (Ｋｏｎｇｅｔａｌ.,1 997) .Ｃｏｎｖｅｎｔｉｏｎａｌｌｙ ,ｄｉｆｆｕｓｉｏｎｃｏｅｆｆｉ ｃｉｅｎｔｓｉｎｇｅｌｓａｒｅｍｅａｓｕｒｅｄｂｙｍｏｎｉｔｏｒｉｎｇｔ…     

长轴深井泵轴承支架水力参数的探讨

轴承支架是长轴深井泵(长轴泵)输水管路的重要组成部分，其水头损失的大小直接影响管路效率的高低。通过对150JD56型长轴泵轴承支架水力参数的测试，提出了长轴泵工作在高效区时轴承支架的局部阻力系数的多元回归分析表达式以及试验所采用的方法和手段，为长轴泵输水管路的合理配套，为促进能耗的降低，为达到高效节能、优化运行以及为当前的机井技术改造提供科学依据。     

依托高等教育人力资源 提升大连人力资源能力

人力资源可划分为3个层次：初级、中级和高级。知识经济时代对高等教育人力资源的需求不断提高，高等教育人力资源成为提升地区人力资源能力的关键。大连应依托高等教育人力资源，提升本地区的人力资源能力。     

陶瓷过滤机运行主要指标的回归分析

运用描述统计和回归分析的方法,建立了用于判断陶瓷过滤机是否高效运行的2个主要指标之间的回归模型。通过模型分析可知,给料浓度和利用系数之间有较强的线性关系,为提高陶瓷过滤机的过滤效率以及对机器的更新升级提供依据。