Power training in elite young soccer players: Effects of using loads above or below the optimum power zone     

Irineu Loturco  Lucas A. Pereira  Valter P. Reis  Chris Bishop  Vinicius Zanetti  Pedro E. Alcaraz 《Journal of sports sciences》2020,38(11-12):1416-1422

ABSTRACT

This study aimed to examine the effects of two jump squat (JS) training programs involving different loading ranges in under-20 soccer players during a preseason period. Twenty-three elite young soccer players performed sprint speed (at 5-, 10-, and 20-m), change-of-direction (COD) speed, JS peak-power (PP), and countermovement jump (CMJ) tests pre and post four weeks of training. Athletes were pair-matched in two groups according to their optimum power loads (OPL) as follows: lower than OPL (LOPL; athletes who trained at a load 20% lower than the OPL) and higher than OPL (HOPL; athletes who trained at a load 20% higher than the OPL). Magnitude-based inferences were used to compare pre- and post-training measures. Meaningful increases in the PP JS were observed for both groups. Likely and possible improvements were observed in the 5- and 10-m sprint velocity in the LOPL group. Meanwhile, possible and likely improvements were observed in the CMJ, 5- and 10-m sprint velocity, and COD speed in the HOPL group. Overall, both training schemes induced positive changes in athletic performance. Soccer coaches and sport scientists can implement the JS OPL-based training schemes presented here, either separately or combined, to improve the physical performance of youth soccer players.  相似文献   

The biomechanical characteristics of high-performance endurance running     

Stephen J. Preece  Christopher Bramah  Duncan Mason 《European Journal of Sport Science》2019,19(6):784-792

The biomechanical profile of high-level endurance runners may represent a useful model that could be used for developing training programmes designed to improve running style. This study, therefore, sought to compare the biomechanical characteristics of high-performance and recreational runners. Kinematic and kinetic measurements were taken during overground running from a cohort of 14 high-performance (8 male) and 14 recreational (8 male) runners, at four speeds ranging from 3.3 to 5.6?m?s^?1. Two-way ANOVA analysis was then used to explore group and speed effects and principal component analysis used to explore the interdependence of the tested variables. The data showed the high-performance runners to have a gait style characterised by an increased vertical velocity of the centre of mass and a flight time that was 11% longer than the recreational group. The high-performance group were also observed to adopt a forefoot strike pattern, to contact the ground with their foot closer to their body and to have a larger ankle moment. Importantly, although observed group differences were mostly independent of speed, the tested variables showed a high degree of interdependence suggesting an underlying unitary phenomenon. This is the first study to compare high-performance and recreational runners across a full range of kinematic and kinetic variables. The results suggest that high-performance runners maintain stride length with a prolonged aerial phase, rather than by landing with a more extended knee. These findings motivate future intervention studies that should investigate whether recreational runners could benefit from instruction to decrease shank inclination at foot contact.  相似文献   

高速数控车削中心主轴单元的可靠性研究   总被引：1，自引：0，他引：1  

王春秀 《宁夏师范学院学报》2001,22(6):16-18

分析讨论了超高速数控车中心主轴单元性能的可靠性要求，对高速数控车削中心的主轴单元典型结构－电主轴的设计进行了详细记述，为车削中心提供了必要的依据和设计方法。  相似文献   

计算机文化基础MOOC平台互动教学实践探索     

任会峰  阚希  陆松  董庆超 《教育技术导刊》2021,19(12):43-47

针对大学各学科培养目标存在差异,以及学生入学时计算机基础不平衡等教育教学现状,依托大规模开放在线课程（MOOC）平台,以计算机文化基础课程为例,从开课前、授课中、结课后3个阶段分别论述开设课程、组织授课和追踪反馈等多个教学环节的实践过程,并形成闭合环路,探索面向应用能力培养的互动教学模式,同时探讨教学中存在的问题及解决办法。抽组测试发现,混合教学的及格率达到98%,相比传统教学提高了18%,约33%的学生自主选择混合式学习,表明MOOC平台的混合教学有利于培养学生的计算思维,提高其计算机应用能力,最后分析MOOC平台采用大数据挖掘技术的重要性和可行性。  相似文献   

变频调速技术在袜机上的应用   总被引：1，自引：0，他引：1  

刘浏 《中国科技信息》2007,(5):85-85,87

本文主要介绍了变频器在袜机应用中系统的构成、控制要点和重要性。  相似文献   

汽轮机调节系统工作不稳定分析   总被引：1，自引：0，他引：1  

史恺 《黑龙江科技信息》2007,(3X):38-38,143

调节系统的不稳定影响汽轮机的生产稳定性，同时给机组的安全运行也带来了不利因素。针对汽轮机调节系统工作不稳定的情况，对其进行了理论的分析，总结归纳了影响汽轮机调节系统工作稳定的各种原因，及其处理措施。  相似文献   

浅析公路路线设计主要技术指标的缺陷     

张军艳 《西安文理学院学报》2011,(4):95-97

针对《公路工程技术标准（》JTG B01-2003）在实际应用中存在的问题,分析了路线设计主要技术指标的缺陷,并提出了处理措施.为进一步选择合理的公路路线设计方案提供了依据.  相似文献   

重机LK1900A型高速套结机机械部分的调整与维修     

冯朝荣 《邢台职业技术学院学报》2011,28(3):96-98

本文从重机LK1900A型高速套结机针杆高度的确定、机针与摆梭配合的调整、压脚高度的调整、移动刀和固定刀的调整、挑线杆位置的调整、机械和电气部分常见故障的排除等几个方面,简要介绍了机器的使用调整与维修方法。  相似文献   

TiO_2涂层与化学镀Ni—P用于铸件表面处理的研究     

赵亚楠 《湖北广播电视大学学报》2011,31(7):156-157

本文采用溶胶—凝胶法先在铸件表面涂覆一层TiO2薄膜,再对铸件进行化学镀Ni—P处理。研究表明,TiO2涂层可以有效减小铸件表面的孔隙率,弥补了Ni—P镀层直接覆盖在铸件表面易产生针孔的缺陷。与现有的铸件表面处理方法相比,本工艺改善了铸件的耐腐蚀性,而且较大地提高了沉积速率。在不增加过多成本的情况下,还节约了能源。  相似文献   

一种加快的CV模型分割方法研究     

张思维 《天中学刊》2011,26(5):13-16

CV模型是一种有效的活动轮廓分割模型,其缺点是分割速度慢.用OTSU法预处理后的区域边界作为CV模型的初始轮廓线,大大提高了分割速度,且该方法能克服传统CV法难以分割壁较厚的内部空洞的不足.在CV模型的能量函数中引入惩罚项,使得CV模型在演化过程中无需重新初始化,进一步提高了分割速度.实验表明改进后的CV模型与传统CV模型相比分割速度有了较大提高,且分割效果更好.  相似文献