耐力、短跑和力量训练后的左心室大小

X射线和尸体解剖的研究结果都曾表明,运动员的心脏比坐位工作的对照组更大,后来用超声心动图进行的研究也证实了这一点。此外,还发现不同项目的运动员之间,心脏大小存在着显著的差异。耐力性运动员具有较大的左心室内径和正常的或稍厚的心室壁,而力量性运动员具有正常的左心室内经和较厚的室壁。短跑运动员的左室壁厚度和     

美国比较教育的发展趋势

比较教育在美国的发展 对比较教育在美国的发展,至今没有完整的分析,这令人感到惊讶。不过,概括二次大战后的一些主要发展趋势还是可能的。本文将简要分析美国近半个世纪以来比较教育的研究和思想体系,说明其基础结构的大致“模式”,阐述它在学术和组织方面的发展趋势。 1.趋势与发展 比较教育始于描述别国的教育制度,该领域关注对别国教育组织模式的了解和教育体系运行机制的描述。它从一开始,就还关心实践和意识形态方     

第一代纳米芯片

随着科学家和工程师们不断突破芯片制造技术的极限，他们已经悄悄进入了纳米领域。     

关于游泳运动员的年龄问题

游泳运动员的年龄变化对拟定多年训练计划和运动成绩的发展都具有十分重要意义。许多科学家和一大批有名望的教练员都对早期专项化提出了批评:儿童少年时期进行极限负荷的训练,将过早地突然地结束运动生涯。奥运会、世界锦标赛和欧洲锦标赛优秀运动员(前八名)的年龄表明:     

Transfer by very young children in the symbolic retrieval task

Cumulative experience with a variety of symbolic artifacts has been hypothesized as a source of young children's increasing sensitivity to new symbol-referent relations. Evidence for this hypothesis comes from transfer studies showing that experience with a relatively easy symbolic retrieval task improves performance on a more difficult task. Significant transfer was found for the 2(1/2)-year-old children in the 3 studies reported here, even with relatively low levels of contextual support (according to the taxonomy of transfer by Barnett & Ceci, 2002). Transfer occurred even though the 2 tasks were encountered in very different settings and there was a prolonged (1-week) delay interval between them. Transfer also occurred to a much more difficult task (one that even 3-year-olds typically fail).     

An epidemiological study of number processing and mental calculation in Greek schoolchildren

The aim of this study was to validate and standardize an instrument for the diagnosis of developmental dyscalculia (mathematics disorder) in a Greek population and to obtain relevant epidemiological data. We used the Neuropsychological Test Battery for Number Processing and Calculation in Children (NUCALC) in a community sample of 240 students ages 7 to 11 years from urban and rural schools. There were no differences between genders in arithmetical performance; however, the effects of grade and socioeconomic level were significant. Prevalence was higher in the rural than in the urban area. A cross-cultural comparison of the Greek data with those obtained with the same instrument in other countries in schoolchildren of the same age was performed.     

Neural issues in the control of muscular strength

During the earliest stages of resistance exercise training, initial muscular strength gains occur too rapidly to be explained solely by muscle-based mechanisms. However; increases in surface-based EMG amplitude as well as motor unit discharge rate provide some insight to the existence of neural mechanisms in the earliest phases of resistance exercise training. Moreover, other phenomena such as the cross transfer of strength following unilateral exercise and neural changes following limb immobilization also support a role for neural control in muscular strength. While studies to date have focused on the phenomenon of neural change, future studies will need to focus on the many motoneuron influences as well as intrinsic motoneuronal properties that may be responsible for these neural adaptations.