Is there really an eccentric action of the hamstrings during the swing phase of high-speed running? Part II: Implications for exercise

We have previously argued that there may actually be no significant eccentric, but rather predominantly an isometric action of the hamstring muscle fibres during the swing phase of high-speed running when the attachment points of the hamstrings are moving apart. Based on this we suggested that isometric rather than eccentric exercises are a more specific way of conditioning the hamstrings for high-speed running. In this review we argue that some of the presumed beneficial adaptations following eccentric training may actually not be related to the eccentric muscle fibre action, but to other factors such as exercise intensity. Furthermore, we discuss several disadvantages associated with commonly used eccentric hamstring exercises. Subsequently, we argue that high-intensity isometric exercises in which the series elastic element stretches and recoils may be equally or even more effective at conditioning the hamstrings for high-speed running, since they also avoid some of the negative side effects associated with eccentric training. We provide several criteria that exercises should fulfil to effectively condition the hamstrings for high-speed running. Adherence to these criteria will guarantee specificity with regards to hamstrings functioning during running. Practical examples of isometric exercises that likely meet several criteria are provided.     

色散条纹传感技术用于拼接镜面位移探测的仿真研究

根据色散条纹传感技术的基本原理,从物理光学的角度对色散条纹传感器(DFS)进行了模拟研究,仿真出理论干涉图形,并从中采集能量信号,拟合光强分布曲线,得出测量结果.通过比较在不同波段的采样,提出在CCD上开出窗口采集有效信号的2种方法,借以提高检测精度.色散条纹传感器的检测范围为±50μm,检测精度可以达到几十nm.     

Continuous and intermittent heat acclimation and decay in team sport athletes

The aim of this study was to compare the impact of continuous (CON) and intermittent (INT) heat acclimation protocols on repeat-sprint performance, and to also assess the degree of performance decay following acclimation. Using a pair-matched, between subjects design, 16 trained male team sport athletes were allocated to either INT (8 sessions over 15 days) or CON acclimation (8 sessions over 8 days) groups. Participants performed a heat tolerance test (HTT) involving 60-min of repeat-sprint cycling with a 10-min half time break (in 35.3?±?0.7°C, 60.1?±?4.0%; RH) two days pre- (pre-HTT) and post-acclimation (post-HTT1). Decay was investigated with two further HTT's completed over the next two weeks (post-HTT2 and post-HTT3). Results showed the post-HTT1 performance variables [mean power (pre-HTT; INT?=?1002.07?±?173.74, CON?=?1057.10?±?180.07 / post-HTT1; INT?=?1097.11?±?186.85, CON?=?1163.77?±?184.65 W), mean power (W.kg^?1), total work (kJ) and work (J.kg^?1)] were greater than pre-HHT (p?p?相似文献   

人工神经网络在光纤智能材料与结构损伤估计中的应用研究

以光纤智能材料与结构中的损伤估计为目的,根据光纤阵列传感信号处理的需要探索了人工神经网络处理信号的原理与结构,给出了BP网的仿真结果。     

大蒜富硒研究进展

硒是人体必需的微量元素,具有抗氧化等多种重要的生物学功能．大蒜作为一种常见的蔬菜,具备较强的硒富集能力．通常可采用土壤施硒,叶面施硒和硒肥浸种三种方式提高大蒜的含硒量,而配合肥料施加的同时、恰当的施硒时机和操作方法也必不可少．并从加强其它蒜原富硒产品研究、提高富硒大蒜综合品质的方法及从种质角度出发如何提升大蒜富硒能力等方面提出了自己的看法．     

新型大学物理实验仪器探讨

为加强大学物理实验室的建设,我校购进了大量的新型大学物理实验仪器,对物理实验教学起到了积极的促进作用。所以对新型大学物理实验仪器的探讨就显得重要。新型大学物理实验仪器多在传统仪器原理的基础上应用传感器设计而成,该类仪器使实验变得简单方便、一目了然,大大提高了实验的效率,减小实验的误差,使实验起到更好的效果。但它们在优化实验环境的同时也存在一定的缺点,这值得我们在实验教学过程中给予关注。     

平面应变有限元法在基坑支护中的应用分析

本文结合沿海某基坑工程,运用Plaxis有限元程序建模并计算,对桩的水平位移、坑底隆起量、应力、桩体及内支撑弯矩、桩体和土体接触面应力进行分析。经实践证明,平面应变有限元法在该基坑支护设计中切实可用,可为类似工程的设计及施工提供一定的参考。     

Assessing the links between punitive parenting,peer deviance,social isolation and bullying perpetration and victimization in South Korean adolescents

Children who are abused at home are at an increased risk of bullying perpetration and bullying victimization. Within that context, the purpose of the present study was to test Agnew’s general strain theory and the peer deviancy training hypothesis by utilizing structural equation modeling to empirically examine pathways linking punitive parenting to bullying perpetration and bullying victimization. This study adds to the literature in two important ways. First, potential mediating linkages between punitive parenting and bullying perpetration and bullying victimization were examined, including socially withdrawn behavior and deviant peer affiliation. Second, these relationships were considered in a longitudinal sample of South Korean adolescents, which is a novel examination given that parenting in South Korea is guided largely by Confucianism which reinforces parental control, restrictiveness, and a punitive nature. Results indicate that: (1) punitive parenting is directly related to bullying perpetration but not bullying victimization; (2) punitive parenting was found to have indirect effects only on bullying perpetration; (3) deviant peer affiliation increased the likelihood of bullying perpetration and victimization; and (4) socially withdrawn behavior only affected bullying perpetration via its effect on deviant peer affiliation.     

物联网的发展前景

物联网是下一代互联网研究的重点,对物联网的关键技术和发展研究已经成为国际和国内业界的热点。本文介绍了物联网的原理和关键技术,并对物联网的发展前景予以了展望。     

分子印迹苄嘧磺隆电流传感器的研制

采用表面分子印迹技术,在硅胶表面合成了苄嘧磺隆印迹聚合物（MIPs）,将MIPs超声分散于氨基苯磺酸溶液中,通过在金电极表面电聚合氨基苯磺酸制备了苄嘧磺隆传感器,采用循环伏安法对电极制备过程进行了表征。