Differences in the utilisation of active power in squat and countermovement jumps     

Damián Ferraro  Gabriel Fábrica 《European Journal of Sport Science》2017,17(6):673-680

The aim of this article was to understand how active power is used in squat and countermovement jumps. A simple empirical model comprising a mass, a spring, an active element and a damper, together with an optimisation principle, was used to identify the mechanical factors that maximise performance of jumps without countermovement (squat jumps, SJ) and with countermovement (CMJ). Twelve amateur volleyball players performed SJ from two initial positions and CMJ with two degrees of counterbalancing, while kinematic data were collected (jump height, push-off duration and position of the centre of mass). The model adjusted well to real data of SJ through all the impulse phase, and slightly less adequately at the end of this phase for CMJ. Nevertheless, it provides a satisfactory explanation for the generation and utilisation of active power for both type of jumps. On average, the estimated power of the active elements, the spring, and the damper were greater in the SJ. Based upon the result obtained with this model, we suggest that active power is best evaluated with SJ. The reason for this is that, during this kind of jump, the elements associated with the damper consume much of the energy produced by the active elements. The participation of the elements that consume the energy generated by the active elements is less in CMJ than in SJ, allowing for a better utilisation of this energy. In this way it is possible to achieve a better performance in CMJ with less active power.  相似文献   

第64届美国运动医学会年会关于“运动益处的生物网络”研究热点与趋势     

何子红 《北京体育大学学报》2017,40(8):40-47

摘要：概述美国运动医学第64th年会的主要内容和目标；归纳“机体对运动反应/适应的生物网络”研究的报告热点；介绍美国国立卫生院资助项目，“人类体力活动的分子传感器”的研究设计和组成。建立各取所长、分工合作的研发联盟是进行运动促进健康分子机制研究的必要途径；基于集合最新研究技术和分析方法，从宏观到微观再到宏观，从整体到局部再到整体的整合性系统实验设计是链接运动益处与其作用机制的桥梁。在未来，该领域的研究成果不仅仅是精准运动的实现、运动依存性的提高和对慢性病的辅助治疗，同时如果能够发现传递运动益处的分子，研发成产品，这必将会为人类健康产生深远影响。  相似文献   

The influence of cycling intensity upon cognitive response during inferred practice and competition conditions     

Michael J. Duncan  Neil D. Clarke  Martin Cox  Mike Smith 《Journal of sports sciences》2017,35(19):1865-1871

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Performing under pressure: Exploring the psychological state underlying clutch performance in sport     

Christian Swann  Lee Crust  Patricia Jackman  Stewart A. Vella  Mark S. Allen  Richard Keegan 《Journal of sports sciences》2017,35(23):2272-2280

Clutch performance is improved performance under pressure. However, little research has examined the psychological state experienced by athletes in these situations. Therefore, this study qualitatively examined the subjective experience underlying clutch performance across a range of sports (e.g., team, individual) and standards (Olympic to recreational athletes). Sixteen athletes (M_age = 27.08 years; SD = 6.48) took part in in-depth, semi-structured interviews primarily after an exceptional performance (M = 4.38 days later; SD = 3.14). Data were analysed inductively and thematically. Clutch states involved 12 characteristics, including heightened and deliberate concentration, intense effort, and heightened awareness, which distinguished the experience of clutch from other optimal psychological states such as flow. Other characteristics, such as perceptions of control, were also reported and supported previous experimental research on clutch. These findings present in-depth qualitative insights into the psychological state underlying clutch performance, and are discussed in relation to the existing literature on optimal psychological states in sport.  相似文献   

What is the Australian National Maritime Museum Ilma collection?     

Dominique Sweeney 《档案与原稿》2019,47(1):153-163

ABSTRACT

The Australian National Maritime Museum (ANMM) in their Darling Harbour warehouse store just over one thousand Ilma. The Ilma are performance symbols of Bardi law and custom, which tell stories of the lands and seas of the Dampier Peninsula, King Sound and surrounding islands of Western Australia. Ilma performances are public and meant for all to see. The ANMM in 2007 resourced detailed documentation of the collection. In 2018 the collection still does not appear on the online catalogue and remains unavailable for public view. While recent efforts have been put into the collection there are important questions to be raised about the responsibility of museums to collections that have contested meanings and serve multiple purposes.  相似文献   

基于STAR-CCM+的汽车挡风玻璃除霜性能提升的仿真分析与研究     

胡忠文 《苏州市职业大学学报》2021,(1)

采用计算流体动力学的方法,利用STAR-CCM+软件对某一车型挡风玻璃除霜性能进行数值模拟分析。通过对出风口格栅进行调整,改变了暖风气流与挡风玻璃之间碰撞角的大小与碰撞点的位置,优化了挡风玻璃表面暖风气流的分布,提升了除霜性能,为汽车除霜风道的设计和改善车辆除霜性能提供了参考。  相似文献   

高职大学英语真实性课程评价方案的设计     

尹衍杰 《邢台职业技术学院学报》2014,(3):11-15

真实性课程评价是近十几年来国际流行的课程评价方式,其能力本位的评价特点,决定其可以在高职大学英语能力培养方面起到重要作用。为实施高职大学英语真实性评价,需要根据高职各专业的英语能力需求,在英语课程评价各个环节进行真实性的设计,其中文化演练部分的评价设计是真实性评价设计的核心。  相似文献   

No harmless child labor: The effect of child labor on academic achievement in francophone Western and Central Africa     

《International Journal of Educational Development》2021

This study empirically examines the effect of child labor on academic achievement in 10 francophone Western and Central African countries. The data were taken from the Programme d’Analyse des Systèmes Educatifs de la CONFEMEN and comprised characteristics of 25,288 grade six students across 1803 schools. Two-stage least squares analysis highlights that child labor undermines academic achievement regardless of subject, gender, and age. It lowers reading and mathematics scores for both genders and for children under 12 and over 13 years. Child labor therefore hinders human capital accumulation in African countries, and it takes place at the cost of future prosperity.  相似文献   

Outstanding performances during elite-standard short and middle-distance finals and the hyperandrogenism regulation—A detailed analysis of Caster Semenya’s results     

Jonathan Ospina-Betancurt  Maria S. Zakynthinaki 《Journal of sports sciences》2020,38(6):703-709

ABSTRACT

Recently, there has been much controversy over the International Association of Athletics Federation (IAAF) regulations regarding eligibility to compete and natural testosterone levels in female athletes. Much interest lies in the analysis of Caster Semenya's extraordinary performance. The objective of this work were, a) Complete an analysis of Caster Semenya's results during the 800m finals and b) search for existing similar performances by other female athletes. We analysed the results of the finals of all IAAF World Championships and Olympic Games from 1984–2016, including the 800m results of the Diamond Leagues 2016–2018. Exponential curves were fit to the data to characterise and predict performance for each event. Caster Semenya's finishing times before her ineligibility to compete and after the suspension of the IAAF hyperandrogenism regulation were found to be 1.24% and 1.49%, respectively, faster than the characteristic performance of the elite-standard in the women’s 800m final. Other female athletes, with finishing times faster than the ones predicted by the characteristic curves were also discovered. The percentage difference in performance between Caster Semenya and the other participants did not reach 3% in the 800m event. No conclusions can be drawn regarding extraordinary results ever performed during the 100m, 200m or 400m finals.  相似文献   

民族传统体育项目在武汉高校开展状况的调查研究     

李伟  付志华  贾海如 《南京体育学院学报(社会科学版)》2016,(4):113-116

采用实地考察法、访谈法、问卷调查法等多种调研方法，对民族传统体育项目在武汉高校开展的状况进行了调查研究。探讨了民族传统体育项目在武汉高校开展的项目种类及该项目的习练人数与指导教师人数，剖析了民族传统体育项目在武汉高校的普及程度与推广标准及该项目习练者的动作规范与演练水平。在分析影响武汉高校民族传统体育项目发展因素的基础上，提出了促进该项目在武汉高校更好地发展的若干对策。  相似文献