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.     

从代理成本角度对我国上市公司资本结构的实证研究

融资结构或资本结构问题一直是公司财务理论研究的重要内容。从隐性融资成本——代理成本的角度研究我国上市公司的资本结构问题，可以为公司财务管理决策者安排合理的融资结构、实现公司价值最大化目标提供决策依据。     

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。     

绵阳旅游业耗散结构系统形成的研究

通过深入考察研究绵阳旅游业系统,发现它属于对称性高、有序度较低的近平衡态系统.为使绵阳旅游业系统成为耗散结构系统,提出了其形成的必要条件和充分条件,并由其充要条件设计了独树一帜的“绵阳城市生态文化景区“.     

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。     

论曹禺戏剧中的意象并置

曹禺戏剧中常常运用意象并置的诗化手段将看似散乱的材料进行“聚”与“收”的处理,以达到对材料深层寓意的充分挖掘。其意象并置的运用普遍而又多样;既有相似意象的对等,又有对比性意象的“跳跃衔接”,还有相同意象的多角度重复,它们与剧中浓郁的叙事性相互对抗,形成戏剧的内在结构张力。     

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。     

钢结构材料在高温(火灾)条件下的力学性能试验研究

从基本的钢结构材料在高温下的力学性能着手 ,进行高温条件下钢结构材料的性能试验 ,建立高温下钢材的屈服强度、极限强度、弹性模量和极限应变随温度变化的力学模型 ,为高温 (火灾 )条件下钢结构的结构分析提供依据。     

浅议隔位修饰现象

文章将多年来在教学中所遇到的一些典型的隔位修饰的例句加以分类归纳 ,旨在帮助学生更好地理解这种句子结构 ,提高他们的阅读理解能力。