An analysis of the relationship between the linear hammer speed and the thrower applied forces during the hammer throw for male and female throwers

The purpose of this study was to investigate the relationship between the cable force and linear hammer speed in the hammer throw and to identify how the magnitude and direction of the cable force affects the fluctuations in linear hammer speed. Five male (height: 1.88 ± 0.06 m; body mass: 106.23 ± 4.83 kg) and five female (height: 1.69 ± 0.05 m; body mass: 101.60 ± 20.92 kg) throwers participated and were required to perform 10 throws each. The hammer's linear velocity and the cable force and its tangential component were calculated via hammer head positional data. As expected, a strong correlation was observed between decreases in the linear hammer speed and decreases in the cable force (normalised for hammer weight). A strong correlation was also found to exist between the angle by which the cable force lags the radius of rotation at its maximum (when tangential force is at its most negative) and the size of the decreases in hammer speed. These findings indicate that the most effective way to minimise the effect of the negative tangential force is to reduce the size of the lag angle.     

An evaluation of biomechanical measures of bowling action legality in cricket

Cricket bowling is traditionally thought to be a rigid-arm motion, allowing no elbow straightening during the delivery phase. Conversely, research has shown that a perfectly rigid arm through delivery is practically unattainable, which has led to rule changes over the past years. The current rule requires a bowler not to increase the elbow angle by more than 15°, thus requiring a measurement to confirm legality in “suspect” bowlers. The aims of this study were to evaluate whether the current rule is maintained over a range of bowlers and bowling styles, and to ascertain whether other kinematics measures may better differentiate between legal and suspect bowling actions. Eighty-three bowlers of varying pace were analysed using reflective markers and a high-speed (240 Hz) eight-camera motion analysis system in a laboratory. The change in elbow segment angle (minimum angle between the arm and forearm), the change in elbow extension angle with respect to the flexion–extension axis of a joint coordinate system, and the elbow extension angular velocity at ball release were measured. We found that bowlers generally bowled within a change in elbow extension angle of 15°. However, this limit was unable to differentiate groups of bowlers from those who were suspected of throwing in the past. Improved differentiation was attained using the elbow extension angular velocity at ball release. The elbow extension angular velocity at ball release may be conceptually more valid than the elbow extension angle in determining which bowlers use the velocity-contributing mechanisms of a throw. Also, a high value of elbow extension angular velocity at ball release may be related to the visual impression of throwing. Therefore, it is recommended that researchers and cricket legislators examine the feasibility of specifying a limit to the elbow extension angular velocity at ball release to determine bowling legality.     

对标枪“引枪”技术动作机制及教法的探讨

从多学科角度来探讨标枪“引枪”动作的机制,阐述了“引枪”动作是人体与标枪两次相对运动的运动学原理,并运用解剖学的有关知识来说明肌肉工作和各环节运动对“引枪”技术的影响,强调要充分利用运动知觉来判断器械正确与否。同时,还对该动作的教法、错误动作的形成原因、纠正方法等进行了论述.     

高频液压振动锤打桩的可打入性分析模型

分别从力学、运动学、能量守恒方程和运动规律的积分方程等方面进行阐述,总结了国外各种高频液压振动锤打桩的可打入性模型的相应原理、假设条件、判断方法及应注意的问题,最后指出了欲进一步预测高频振动锤打桩的可打入性应考虑的几个问题.     

我国优秀女子链球运动员最后用力阶段投掷技术的运动学研究

采用现场技术采集与运动生物力学解析的方法,对第11届全国运动会女子链球决赛前8名运动员最后用力投掷技术进行运动学研究。结果表明,掷链球最后用力技术由单支撑和双支撑两部分构成;我国优秀女子链球运动员最后用力阶段链球一直处于加速状态,但是链球速度的增量对出手速度的贡献不是很大;单支撑最后用力阶段肩髋轴间夹角较小,链球与肩轴的夹角较大,以致影响了最后的用力效果。     

我国女子链球运动员专项能力结构及评价标准的研究

运用文献资料法、特尔菲法、问卷调查法、专家访谈法、数理统计等方法从专项训练学角度研究了我国女子链球运动员专项能力结构及评价标准,建立了我国女子链球运动员专项能力指标体系、预测模型,制定了我国女子链球运动员专项能力评价标准及评价方法,并列举了应用实例。为我国女子链球运动员专项能力定量监控、板块训练提供了方法学途径和条件,这种从运动专项本体角度进行方法学问题研究意义重大,有助于推动我国专项训练学的发展,特别是在多赛事的今天更具有现实指导意义。     

对女子链球运动员冬季准备期力量训练的研究

通过跟踪北京体育大学链球队女子运动员冬训期的训练,对两名运动员冬季准备期的力量训练进行分析和研究,总结出了链球运动员在冬季准备期的力量训练方法、手段和负荷结构。通过对运动员的力量素质的发展变化进行评价,根据评价结果采取针对性的力量训练手段。     

锤击式沉管灌注桩常见的质量问题及其处理

本文分析了锤击式沉管灌注桩施工中几种常见的质量问题及处理办法,对实际施工有一定的指导意义.     

我国优秀女子链球选手最后用力技术运动学特征的研究

通过三维运动学分析的方法,对我国现役的3名优秀女子链球运动员的投掷技术进行研究,发现王峥单支撑时间较短,身体转动快,右脚着地积极,上下肢扭紧情况好,下肢缓冲的幅度小,重心起伏程度小,最后用力中左腿撑蹬效果不好.廖晓燕的缓冲时间短,重心移动快,在水平方向速度小,垂直方向的速度大,上下起伏程度大,最后用力中存在右肩提前对器械加速的现象.张永莉单支撑时间长,缓冲时间长,右脚着地瞬间重心偏左,重心速度保持的不好,上下起伏程度较大,缓冲瞬间下肢缓冲幅度小,力量向前性不好等问题.     

链球运动起源新探

链球一直被认为起源于苏格兰,但最近发现的一块西晋画像砖给人们展示了我国最早的掷链球形态.从历史、地理、哲学等角度对这一画像砖进行考析,旨在探讨链球运动的起源,通过史料分析认为链球运动起源于中国具有较大的可能性.