乒乓球运动员上肢等速肌肉力量的评定

利用Biodex 等速测力系统,对北京体院体育系、运动系乒乓球专业学生25人进行角速度为60(°)/s、270(°)/s、450(°)/s 的腕、肘、肩各关节屈伸肌力的等速测试,首次为乒乓球运动员的上肢肌力提供了参考值。研究表明,最大力矩值与上臂围度、前臂围度和握力、背力等有统计学意义;上肢肌力不能反映扣球的远度。     

螺纹紧固件拧紧扭矩的确定方法研究

为在满足使用要求的情况下充分发挥螺纹紧固件的效能,提出了拧紧扭矩计算的预紧力-扭矩特性曲线法。分析过程中,通过理论推导和实验分析,得到了在拧紧过程中等效拉应力与实际拉应力的关系式;并得到了当螺纹紧固件在拧紧至屈服之前,螺纹摩擦扭矩与拧紧总扭矩之比不变的结论。运用预紧力-扭矩特性曲线法对某汽车发动机承重螺栓的拧紧扭矩进行计算,通过与实际扭矩值进行比较,表明该方法更能发挥螺栓的使用效能。     

CMAC神经网络在变磁阻电动机转矩控制中的应用

结合变磁阻电动机的工作特点,提出了应用小脑模型神经网络控制SRM转矩的控制器结构和改进的学习算法。该算法是在原算法的基础上增加了一个与可变相角有关的约束函数。仿真结果表明:该系统不但收敛速度没有降低,而且经过训练能够产生理想的电流曲线,在抑制电机转矩脉动和提高有效功率方面具有显著效果。     

女子柔道运动员减重期力量变化及营养干预效果研究

目的:通过对减体重期运动员力量变化及营养干预效果研究,探讨提高运动员运动能力、充分发挥其竞技水平的方法和手段.实验对象:内蒙古女子柔道队员,按体重随机配对分为普通减重组(n=8)、普通营养减重组(n=8)和营养干预减重组(n=8).实验步骤:实验期为2周,普通营养减重组补充多种维生素及矿物质,另加适量的低聚糖;营养干预减重组除补充多种维生素、矿物质以外,还补充谷氨酰胺等营养补剂.两周训练安排以大强度为主.结果发现:补充无机盐、维生素特别是谷氨酰胺等营养补剂能有效地提高运动员的运动能力,改善运动员的身体机能状态,但是,实验前后各组间运动员的各项峰力矩指标都没有显著性差异(P＞0.05),这在一定程度上表明不能高估补充营养物质的作用.     

等速测试在评价运动员肌力中的应用

运用文献资料法和专家访谈法对等速测试评价运动员肌力测试方法、指标分析、具体应用和测试中存在的问题几方面进行综述。等速测试作为运动员肌力评价的手段有着较高的使用价值,是一种较先进的一般力量测评手段。但等速测试技术自身存在一些技术瓶颈,而且在测试方法选择上有待统一和完善。     

掷标枪运动员主要关节屈伸肌峰力矩初探

采用澳大利亚KEYLINK公司生产的等速肌力测试系统,对男子标枪运动员肩、肘、髋关节肌肉力量进行等速向心测试,测试速度分别设定为60o/s,180o/s(肩120o/s)。测试的结果表明:屈伸肌由60o/s到120o/s或180o/s时,肩、肘屈伸肌和髋伸肌峰力矩、相对峰力矩减小,髋屈肌峰力矩、屈伸肌相对峰力矩增大;肩、髋屈伸比增大,肘屈伸比减小;屈肌快速力/绝对力比值大于伸肌。     

Mechanical energy generation and transfer in the racket arm during table tennis topspin backhands

The ability to generate a high racket speed and a large amount of racket kinetic energy on impact is important for table tennis players. The purpose of this study was to understand how mechanical energy is generated and transferred in the racket arm during table tennis backhands. Ten male advanced right-handed table tennis players hit topspin backhands against pre-impact topspin and backspin balls. The joint kinetics at the shoulder, elbow and wrist of the racket arm was determined using inverse dynamics. A majority of the mechanical energy of the racket arm acquired during forward swing (65 and 77% against topspin and backspin, respectively) was due to energy transfer from the trunk. Energy transfer by the shoulder joint force in the vertical direction was the largest contributor to the mechanical energy of the racket arm against both spins and was greater against backspin than against topspin (34 and 28%, respectively). The shoulder joint force directed to the right, which peaked just before impact, transferred additional energy to the racket. Our results suggest that the upward thrust of the shoulder and the late timing of the axial rotation of the upper trunk are important for an effective topspin backhand.     

液力变矩器液黏零速加载试验系统的研制

介绍一种可以实现液力变矩器零速加载的试验系统。为完成液力变矩器的性能试验,特别是液力变矩器零速工况试验,应用液体黏性传动技术设计了液黏零速加载试验系统。试验系统由动力及其控制系统、液黏测功加载及其辅助系统和测控系统组成。试验系统利用电液比例控制技术实现液黏测功机加载转矩控制,应用虚拟仪器思想实现试验数据采集与处理。液黏零速加载试验系统具有广阔的应用前景。     

鼠笼式多相异步电动机转矩的讨论

从对鼠笼式三相异步电动机转子电流相数的分析,对其转矩的表示式进行了详细的讨论。     

Sport selection in under-17 male roller hockey

Abstract

Characteristics of 32 international and 41 local under-17 (U-17) (14.5–16.5 years) roller hockey players were considered in the context of discrimination by competitive level using training history, anthropometry, skeletal maturation, and several laboratory and field performance tests. More international (42%) than local (22%) players were advanced in maturity status. International players had slightly less hockey experience (years), but had more practice sessions and match time (minutes) during the season. Local players were shorter and attained better performance in the 25-m dash, while international players performed better in sit-ups, ball throw and 20-m shuttle run. The fatigue index derived from the Wingate anaerobic test was higher among local players, while peak torques of knee extension and flexion were greater in international players. Stepwise discriminant function correctly classified 85% of players by competitive level based on grip strength, ratio of eccentric and concentric knee extension, number of training sessions, playing time and fatigue index. The results suggested an interaction among strength, anaerobic fitness and training plus game time as factors in discriminating international from local level players and by inference in the selection and development of youth roller hockey players.