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。     

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.     

智能化电机测功机实验装置的研制

对他励式电机测功机进行研究，研制出电机测功机实验装置，并设计出单片机数据采集系统对电机转矩进行智能化测量，为学生电机实验提供了良好的条件。     

车用涡轮增压柴油机低速和加速性能研究分析

随着涡轮增压柴油发动机转速下降,其外特性降低,转矩减小,与车用柴油机需扭矩增大不符.为了使其性能与柴油机在负荷和转速变化频繁的整个工作范围内有一良好匹配,需选用合适的增压器和排气系统等来提高其低速和加速性能.     

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。     

Interferential therapy effect on mechanical pain threshold and isometric torque after delayed onset muscle soreness induction in human hamstrings

Abstract

This study was undertaken to examine the acute effect of interferential current on mechanical pain threshold and isometric peak torque after delayed onset muscle soreness induction in human hamstrings. Forty-one physically active healthy male volunteers aged 18?33 years were randomly assigned to one of two experimental groups: interferential current group (n = 21) or placebo group (n = 20). Both groups performed a bout of 100 isokinetic eccentric maximal voluntary contractions (10 sets of 10 repetitions) at an angular velocity of 1.05 rad · s^?1 (60° · s^?1) to induce muscle soreness. On the next day, volunteers received either an interferential current or a placebo application. Treatment was applied for 30 minutes (4 kHz frequency; 125 μs pulse duration; 80?150 Hz bursts). Mechanical pain threshold and isometric peak torque were measured at four different time intervals: prior to induction of muscle soreness, immediately following muscle soreness induction, on the next day after muscle soreness induction, and immediately after the interferential current and placebo application. Both groups showed a reduction in isometric torque (P < 0.001) and pain threshold (P < 0.001) after the eccentric exercise. After treatment, only the interferential current group showed a significant increase in pain threshold (P = 0.002) with no changes in isometric torque. The results indicate that interferential current was effective in increasing hamstrings mechanical pain threshold after eccentric exercise, with no effect on isometric peak torque after treatment.     

The influence of electrostimulation on mechanical and morphological characteristics of the triceps surae

The present study assessed the effects of training using electrostimulation of muscle (EMS) on the torque‐angular velocity and torque‐angle relationships, and the cross‐sectional area (CSA) of the triceps surae. Twelve physical education students, divided into two groups (6 control, 6 experimental), participated in the experiment. The EMS sessions were undertaken using a ‘Compex‐type’ stimulator. Flexible elastomer electrodes were used. The current used discharged pulses lasting for 200 μs at a frequency of 70 Hz. The durations of contraction and rest were 5 and 15 s, respectively. The session lasted for 10 min for each muscle. The training regimen was three sessions per week for 4 weeks. Biomechanical tests were performed with the Biodex (Biodex Corporation, Shirley, NY, USA) isokinetic ergometer. Plantar flexions of the ankle over a concentric range of voluntary contractions were performed at different angular velocities (1.05, 2.10, 3.14, 4.20, 5.23 and 6.28 rad s^‐1) and maximum voluntary isometric contractions were held for 5 s at several ankle flexion angles (–30°, –15°, 0° and 15°; 0° corresponds to foot flexion of 90° relative to the leg axis). The peak value of the torque was recorded. Morphological tests consisted of measuring the CSA of the triceps surae on the right leg, 15 cm below the tibial protuberance, by a computerized tomography technique. The torque‐velocity relationship was seen to shift significantly upwards after EMS training. The increase in the isometric torque observed after EMS training was greater in dorsiflexion than in plantarflexion. No change was noted in the CSA of the muscle. It appears that the increase in strength following EMS training is not related to an increase in the contractile matter. These observations show that EMS training for 4 weeks develops dynamic and static contractile properties of the muscle. Neural mechanisms may account for these adaptations.     

The effects of imagery training on fast isometric knee extensor torque development

Abstract

We hypothesized that imagery training would improve the fast onset of neuromuscular activation and thereby fast knee extensor isometric torque development. Forty young healthy participants, not involved in strength training, were assigned to one of four groups: physical training, imagery training, placebo training or control. The three training groups had three 15 min sessions per week for 4 weeks, with a 90° knee angle but were tested also at 120°. At 90° knee angle, maximal torque increased (～8%) similarly in all three training groups. The torque–time integral (contractile impulse) over the first 40 ms after torque onset (TTI40) increased (P < 0.05) after physical training (by ～100%), but only at 90°. This increase was significantly different from the delta values (change pre to post) in the control and placebo groups, whereas delta values in the imagery group were similar to those in the placebo group. The increases in TTI40 following physical training were related (r ² = 0.81, P < 0.05) to significant increases of knee extensor rectified surface EMG at torque onset (EMG40). In conclusion, only physical training led to a knee angle specific increase of contractile impulse that was significantly different from placebo and controls and that was related to improved onset of neuromuscular activation.     

虚拟应急演练系统的设计与实现

虚拟应急演练系统基于Torque3D游戏引擎开发,以应急预案为蓝本,以灾害伤害模型为理论依据,实现了灾害场景设置、事件注入、事件接报、事件分析研判、决策标绘、演练执行、演练总结等一系列应急演练流程。该系统能够体现应急预案的处置流程,训练各不同部门在应急处置过程中协作能力,检验各相关人员对预案实施的执行能力。