Time course of recovery of vertical jump height and heart rate versus running speed after a 90-km foot race     

Alan M Nevill  Roger L Holder  Arthur D Stewart 《Journal of sports sciences》2013,31(7):645-650

It is well known that sport and exercise play an important role in stimulating site-specific bone mineral density (BMD). However, what is less well understood is how these benefits dissipate throughout the body. Hence, the aim of the present study was to compare the BMD (recorded at nine sites throughout the skeleton) of 106 male athletes (from nine sports) with that of 15 male non-exercising age-matched controls. Given that BMD is known to increase with body mass and peak with age, multivariate and univariate analyses of covariance were performed to compare the BMD of the nine sports groups with controls (at all sites) using body mass and age as covariates. Our results confirmed a greater adjusted BMD in the arms of the upper-body athletes, the right arm of racket players and the legs of runners (compared with controls), supporting the site-specific nature (i.e. specific to the externally loaded site) of the bone remodelling response (all P?<0.01). However, evidence that bone mass acquisition is not just site-specific comes from the results of the rugby players, strength athletes, triathletes and racket players. The rugby players' adjusted BMD was the greatest of all sports groups and greater than controls at all nine sites (all P?<0.01), with differences ranging from 8% greater in the left arm to 21% in the lumbar spine. Similarly, the strength athletes' adjusted BMD was superior to that of controls at all sites (P?<0.05) except the legs. The adjusted BMD of the triathletes was significantly greater than that of the controls in both the arms and the legs as well as the thoracic and lumbar spine. The racket players not only had significantly greater right arm BMD compared with the controls but also a greater BMD of the lumbar spine, the pelvis and legs. In contrast, the low-strain, low-impact activities of keep-fit, cycling and rowing failed to benefit BMD compared with the age-matched controls. These results suggest that sporting activities involving high impact, physical contact and/or rotational forces or strains are likely to convey significant benefits not only to the loaded sites, but also to other unloaded peripheral and axial sites throughout the skeleton.  相似文献   

世界原油价格波动对我国农产品价格影响实证分析   总被引：2，自引：1，他引：1  

卢福财  何文章 《软科学》2013,27(4)

以2002年1月～2011年12月的世界原油期货价格和我国农产品玉米、小麦、大豆以及猪肉价格的月度数据时间序列为例,运用单位根检验、协整检验、脉冲响应函数以及方差分解等时间序列技术,对世界原油价格波动与我国农产品价格变化关系进行实证分析。结果发现,我国农产品价格影响因素最大的是其自身的供需关系,而世界原油价格波动对我国农产品价格影响的大小不均衡,对玉米、小麦影响较大,而对猪肉价格影响不显著。  相似文献   

Variability in Measurement of Swimming Forces     

Rod Havriluk 《Research quarterly for exercise and sport》2013,84(2):32-39

An analysis was conducted to identify sources of true and error variance in measuring swimming drag force to draw valid conclusions about performance factor effects. Passive drag studies were grouped according to methodological differences: tow line in pool, tow line in flume, and carriage in tow tank. Active drag studies were grouped according to the theoretical basis: added and/or subtracted drag (AAS), added drag with equal power assumption (AAE), and no added drag (ANA). Data from 36 studies were examined using frequency distributions and meta-analytic procedures. It was concluded that two active methods (AAE and ANA) had sources of systematic error and that one active method (AAS) measured an effect that was different from that measured by passive methods. Consistency in drag coefficient (Cd) values across all three passive methods made it possible to determine the effects of performance factors.  相似文献   

体育专业学生显性身体素质课程实验研究——以四川民族学院体教10级本科为例     

蒲西安  游敏 《体育科技文献通报》2013,(10):48-49,60

用T检验、卡方检验和回归分析,对在体育专业学科教学中,采用每星期加开一次课（90分钟）的身体素质显性课程教学和没有加开身体素质显性课程教学进行一年的教学实验研究,其结果表明：（对照组）没有开设身体素质显性课程的学生100米、铅球和立定跳远成绩均不如（实验组）每星期加开一次身体素质显性课程教学的班级,实验组经过一年的实验后各项身体素质均有大幅度提高,实验组和对照组的身体素质水平呈非常显著性差异。此研究为今后体育专业课程设置和教学改革提供理论依据。  相似文献   

超几何分布的期望和方差的一种新求法     

马松林 《巢湖学院学报》2006,8(3):139-140

本文介绍如何运用概率母函数来求超几何分布的期望和方差  相似文献   

4-6年级小学生心理健康状况的调查分析     

张涛  邱同和 《培训与研究》2002,19(3):90-92

本采用MHT对449名小学生的心理健康状况进行了调查，通过统计分析发现：（1）全体学生在八个分量表的平均分上有显性差异。（2）总量表和分量表（恐怖倾向量表除外）的平均分均无显性性别差异（3）总量表的平均分随年级升高而增高，四年级学生和六年级学生存在显性差异。  相似文献   

菲汀提取工艺的试验研究     

李芳 《忻州师范学院学报》2002,18(5):44-45

用正交设计法设计了菲汀提取条件的方案,并对试验结果进行了方差分析。结果表明:沉淀剂的变化对菲汀收率的影响非常显著。  相似文献   

J函数的边际修正估计及比较     

赵占平  鄢川江 《天中学刊》2007,22(2):1-3

J函数是1-G(t)和1-F(t)的比值.文章把关于G(t)和F(t)的估计扩展到J(t)并对其进行了比较研究,包括偏差、样本方差和最大偏离的比较.  相似文献   

我国外汇储备对货币供给时滞的影响     

岳意定  周双红  张璇 《湖南师范大学社会科学学报》2007,36(3):89-92

在开放经济条件下,作为本外币政策的连接点,外汇储备及其变动改变了货币政策的传导过程,影响从基础货币投放到实现货币扩张的速度,即货币供给时滞.我们运用基于自向量回归(VAR)模型的脉冲响应函数和方差分解分析对我国外汇储备对货币供给时滞的影响进行实证研究,证明了外汇储备的增加会缩短货币供给的时滞,并且其对广义货币供给时滞的影响比对狭义货币更明显.  相似文献   

中职生与普高生自我概念的差异分析与思考   总被引：1，自引：0，他引：1  

何以建 《职业技术教育》2003,24(1):60-62

作为联系个体内心世界与外部世界的惟一纽带——自我概念，对学生的学习行为有着决定性的影响。本文对中职生与普高生的学业自我概念和非学业自我概念进行调查和对比分析，认为目前中职生学业自我概念低下的状况亟待改变，必须深化教育教学改革，从而帮助中职生发展积极的自我概念，不断提高学习质量。  相似文献