Relationship between the peak time of hamstring stretch and activation during sprinting

The purpose of this study was to investigate the time series relationships between the peak musculotendon length and electromyography (EMG) activation during overground sprinting to clarify the risk of muscle strain injury incidence in each hamstring muscle. Full-body kinematics and EMG of the right biceps femoris long head (BFlh) and semitendinosus (ST) muscles were recorded in 13 male sprinters during overground sprinting at maximum effort. The hamstring musculotendon lengths during sprinting were computed using a three-dimensional musculoskeletal model. The time of the peak musculotendon length, in terms of the percentage of the running gait cycle, was measured and compared with that of the peak EMG activity. The maximum length of the hamstring muscles was noted during the late swing phase of sprinting. The peak musculotendon length was synchronous with the peak EMG activation in the BFlh muscle, while the time of peak musculotendon length in the ST muscle occurred significantly later than the peak level of EMG activation (p < 0.05). These results suggest that the BFlh muscle is exposed to an instantaneous high tensile force during the late swing phase of sprinting, indicating a higher risk for muscle strain injury.     

Effects of power variation on cycle performance during simulated hilly time-trials

It has previously been shown that cyclists are unable to maintain a constant power output during cycle time-trials on hilly courses. The purpose of the present study is therefore to quantify these effects of power variation using a mathematical model of cycling performance. A hypothetical cyclist (body mass: 70?kg, bicycle mass: 10?kg) was studied using a mathematical model of cycling, which included the effects of acceleration. Performance was modelled over three hypothetical 40-km courses, comprising repeated 2.5-km sections of uphill and downhill with gradients of 1%, 3%, and 6%, respectively. Amplitude (5–15%) and distance (0.31–20.00?km) of variation were modelled over a range of mean power outputs (200–600?W) and compared to sustaining a constant power. Power variation was typically detrimental to performance; these effects were augmented as the amplitude of variation and severity of gradient increased. Varying power every 1.25?km was most detrimental to performance; at a mean power of 200?W, performance was impaired by 43.90?s (±15% variation, 6% gradient). However at the steepest gradients, the effect of power variation was relatively independent of the distance of variation. In contrast, varying power in parallel with changes in gradient improved performance by 188.89?s (±15% variation, 6% gradient) at 200?W. The present data demonstrate that during hilly time-trials, power variation that does not occur in parallel with changes in gradient is detrimental to performance, especially at steeper gradients. These adverse effects are substantially larger than those previously observed during flat, windless time-trials.     

基于仙人掌发展模型的“晒”的隐喻性词义演变

"晒"是现代汉语中的基本词汇,在词义演化过程中,"晒"的隐喻性语义演化不仅能体现出词义辐射型的优势,各种引申义能直接指向"晒"的基本义,而且发挥了连锁型的优势,加强了各引申义之间的紧密联系。"晒"的不同语义之所以能纳入到统一的语义框架中,是因为它们之间存在着差异的同时又表现出某种程度的相似性,这种相似性可通过仙人掌发展模型进行分析,显示了词语语义链发展的新特征。     

工科《线性代数》总复习框架

将工科《线性代数》中所涉及到的知识点用一条脉络串起来,各个知识点之间的相互关系清晰明了,同时也将《线性代数》这门课程要求学生掌握的知识体系体现出来.     

程序民主的完美典范:雅典陪审法庭

本文借助文本资料和考古资料,重现了古代雅典陪审法庭的运作过程。在此基础上,作者提出,雅典人以平等、公平、公正为目标,通过把陪审员名额分配上的硬性规定与分配法庭时的弹性机率、程序的公开性与投票的秘密性相结合,并配以对程序协助者的监督,从而创造了古典社会中程序民主的典范。     

面向在校大学生培养党政后备人才模式纵论

在实施人才强国战略中,建立党政后备人才培养体系是加强党的执政能力建设,从更高的战略层面推进人才队伍建设可持续发展的重要举措。面对日益激烈的人才竞争,大学生成为党政后备人才资源群体有其历史的合理性;面向在校大学生培养党政后备人才要立足于当代大学生的现实特点和后备人才的未来的双重视角,充分关注其特殊性,着重培养强化他们的政治思维素质、社会责任感、理论联系实际能力、健全的个性心理品质、完善和谐的人格。面向在校大学生培养党政后备人才模式,对广大经济欠发达地区具有普适性。     

开放型实验室管理模式探讨

讨论了开放型实验室需要解决的问题及其管理模式，并介绍了实践经验。     

应用管理系统在局域网中的总体设计

随着计算机关系型数据库语言的丰富与完善,特别是FOXBASE最新一代的数据库管理系统软件的出现,以及各种管理系统开发工具软件的使用,使得在开发一个计算机系统时,最感困难和复杂的已不再是具体程序的编写,而是整个系统的规划。大连市委组织部开发的《大连市组织工作信息管理网络系统》即是整个系统的规划在局域网络中的总体设计的想法和思路。     

让学生学会做数学——课改下的数学教学新理念

新课标要求数学教学要让学生学会“做数学”,做数学”的目的最终是要让学生学会“数学化”。“做数学”的实质是把重点从“教”转向“学”,从教师的行为转向学生的活动,并且从感觉效应转向活动效应,使学生在数学的活动中感知数学、认识数学、体验数学和应用数学。     

阅读教学中培养学生自主学习能力的操作原则

目前大力倡导的自主学习能力不是学生天生固有的,而是教师引导培养的结果。要培养学生自主学习能力应遵循如下三条原则,即个体性原则、思维性原则、活动性原则。