上海女子自行车运动员冲刺骑行中的下肢运动学评价

对女子短距离自行车运动员45 s全力冲刺骑行进行下肢运动学分析,探讨不同水平运动员速度能力的特点,筛选可评价下肢踏蹬技术的运动学指标。使用三维红外运动捕捉系统及SRM自行车测功仪,采集上海自行车队4名女子短距离运动员场地车滚筒练习台上45 s全力冲刺骑行中的下肢运动学参数和踏频。结果表明,钟××速度能力较好,45 s全力冲刺骑行各阶段平均速度较高,但下肢踏蹬"圆滑度"还需进一步提高;顾××和姚××后程速度下降明显,速度耐力明显不足。在全力冲刺骑行后期,运动水平较高的运动员（钟××）踝关节活动度下降明显小于运动水平较低的运动员（顾××和姚××）,提示踝关节活动度下降是影响自行车短距离项目运动员速度耐力的因素之一。     

An accurate estimation of the horizontal acceleration of a rower’s centre of mass using inertial sensors: a validation

For a valid determination of a rower’s mechanical power output, the anterior–posterior (AP) acceleration of a rower’s centre of mass (CoM) is required. The current study was designed to evaluate the accuracy of the determination of this acceleration using a full-body inertial measurement units (IMUs) suit in combination with a mass distribution model. Three methods were evaluated. In the first two methods, IMU data were combined with either a subject-specific mass distribution or a standard mass distribution model for athletes. In the third method, a rower’s AP CoM acceleration was estimated using a single IMU placed at the pelvis.

Experienced rowers rowed on an ergometer that was placed on two force plates, while wearing a full-body IMUs suit. Correspondence values between AP CoM acceleration based on IMU data (the three methods) and AP CoM acceleration obtained from force plate data (reference) were calculated. Good correspondence was found between the reference AP CoM acceleration and the AP CoM accelerations determined using IMU data in combination with the subject-specific mass model and the standard mass model (intraclass correlation coefficients [ICC] >?0.988 and normalized root mean square errors [nRMSE]?3.81%). Correspondence was lower for the AP CoM accelerations determined using a single pelvis IMU (0.877?Based on these results, we recommend determining a rower’s AP CoM acceleration using IMUs in combination with the standard mass model. Finally, we conclude that accurate determination of a rower’s AP CoM acceleration is not possible on the basis of the pelvis acceleration only.     

对影响短跑成绩提高的外源性生物力学因素的研究

影响短跑成绩提高的因素很多,其中外源性生物力学因素容易被大多数教练员忽视。外源性生物力学因素属力学类范畴,它是由身体质量、空气助力和地球的引力等构成。通过对影响短跑成绩提高的这些力学因素,对如何通过训练手段、鞋、服装以及运动场地的设计来克服这些力学因素,以求达到提高速度的目的。     

《运动生物力学》本科教材名词术语辨析

对《运动生物力学》本科教材中运动生物力学的概念,人体基本运动动作形式——推、拉、缓冲及摆动的定义、实例及特点进行辨析,旨在为建设科学性与系统性相统一,时代性与先进性相结合,基础性与应用性相联系的教材提供参考。认为,最新版《运动生物力学》教材中的部分概念、定义仍然不够严密,主要表现在两个方面：第一,运动生物力学的概念不能反映学科特点,也不利于学科发展。第二,对人体基本运动形式——推、拉、缓冲、摆动的特点理解尚不够深入,其定义存在三种逻辑上的错误：定义中有被定义的词出现;定义中某些术语的内涵、外延与运动解剖学不一致;所举实例与定义不符。建议修订教材前对以上内容进行深入探讨。     

从生物力学看低姿匍匐训练

目前在低姿匍匐训练中,普遍存在动作速度慢、身体姿势高等不足,为揭示其运动规律,选取部分优秀学员为研究对象,采用运动生物力学研究方法进行研究.结果发现,低姿匍匐是周期性动作,分为两个阶段;下肢的伸展动作是低姿匍匐的关键环节,但上肢的配合也很重要;训练中要遵循“低”和“快”的原则.     

Anticipation by basketball defenders: An explanation based on the three-dimensional inverted pendulum model

Abstract

We previously estimated the timing when ball game defenders detect relevant information through visual input for reacting to an attacker's running direction after a cutting manoeuvre, called cue timing. The purpose of this study was to investigate what specific information is relevant for defenders, and how defenders process this information to decide on their opponents' running direction. In this study, we hypothesised that defenders extract information regarding the position and velocity of the attackers' centre of mass (CoM) and the contact foot. We used a model which simulates the future trajectory of the opponent's CoM based upon an inverted pendulum movement. The hypothesis was tested by comparing observed defender's cue timing, model-estimated cue timing using the inverted pendulum model (IPM cue timing) and cue timing using only the current CoM position (CoM cue timing). The IPM cue timing was defined as the time when the simulated pendulum falls leftward or rightward given the initial values for position and velocity of the CoM and the contact foot at the time. The model-estimated IPM cue timing and the empirically observed defender's cue timing were comparable in median value and were significantly correlated, whereas the CoM cue timing was significantly more delayed than the IPM and the defender's cue timings. Based on these results, we discuss the possibility that defenders may be able to anticipate the future direction of an attacker by forwardly simulating inverted pendulum movement.     

Effect of swimming velocity on arm coordination in the front crawl: a dynamic analysis

We examined the preferred mode of arm coordination in 14 elite male front-crawl swimmers. Each swimmer performed eight successive swim trials in which target velocity increased from the swimmer's usual 3000-m velocity to his maximal velocity. Actual swim velocity, stroke rate, stroke length and the different arm stroke phases were then calculated from video analysis. Arm coordination was quantified by an index of coordination based on the lag time between the propulsive phases of each arm. The index expressed the three coordination modes in the front crawl: opposition, catch-up and superposition. First, in line with the dynamic approach to movement coordination, the index of coordination could be considered as an order parameter that qualitatively captured arm coordination. Second, two coordination modes were observed: a catch-up pattern (index of coordination?=??8.43%) consisting of a lag time between the propulsive phases of each arm, and a relative opposition pattern (index of coordination?=?0.89%) in which the propulsive phase of one arm ended when the propulsive phase of the other arm began. An abrupt change in the coordination pattern occurred at the critical velocity of 1.8?m?·?s^?1, which corresponded to the 100-m pace: the swimmers switched from catch-up to relative opposition. This change in coordination resulted in a reorganization of the arm phases: the duration of the entry and catch phase decreased, while the duration of the pull and push phases increased in relation to the whole stroke. Third, these changes were coupled to increased stroke rate and decreased stroke length, indicating that stroke rate, stroke length, the stroke rate/stroke length ratio, as well as velocity, could be considered as control parameters. The control parameters can be manipulated to facilitate the emergence of specific coordination modes, which is highly relevant to training and learning. By adjusting the control and order parameters within the context of a specific race distance, both coach and swimmer will be able to detect the best adapted pattern for a given race pace and follow how arm coordination changes over the course of training.     

世界优秀女子铅球运动员背向滑步推铅球技术的生物力学分析

运用文献资料法、数理统计法和比较分析法,对2009年柏林世界田径锦标赛女子铅球前八名运动员的技术动作进行生物力学分析。结果表明：优越的身体形态条件是成为世界一流铅球运动员的基础;在滑步开始阶段奖牌获得者就具备了较高的身体重心速度,滑步和最后用力阶段与其他运动员没有太大区别,过渡阶段要高于其他运动员;过渡阶段奖牌获得者的肩轴和髋轴平均角速度大于其他运动员,两者之差呈减小趋势;在最后用力阶段奖牌获得者能在最短的时间获得较大的速度增量和加速度;出手速度是获得较好运动成绩的主导因素,出手角度、出手高度与运动员各自技术特点有一定的关系。     

Strapping rowers to their sliding seat improves performance during the start of ergometer rowing

Abstract

Rowers sit on a seat that slides relative to the boat/ergometer. If a rower lifts him or herself from this sliding seat at any time, the seat will move away from under them and the rowing action is disrupted. From a mechanical perspective, it is clear that the need for the rower to remain in contact with the sliding seat at all times imposes position-dependent constraints on the forces exerted at the oar handle and the footstretcher. Here we investigate if the mechanical power output during rowing, which is strongly related to these forces, might be improved if the contact with the sliding seat was of no concern to the rower. In particular, we examine if elimination of these constraints by strapping the rower to the sliding seat leads to an increase in performance during the start on a standard rowing ergometer. Eleven well-trained female rowers performed 5-stroke starts in normal and strapped conditions. Handle force, vertical seat force, footstretcher force, and handle kinematics were recorded, from which mechanical power and work output were calculated. Most of the relevant mechanical variables differed significantly between the normal and strapped conditions. Most importantly, mechanical power output (averaged over the 5-stroke start) in the strapped condition was 12% higher than in the normal condition. We conclude that strapping a rower's pelvis to the sliding seat allows more vigorous execution of the stroke phases, resulting in a substantial improvement in performance during the start of ergometer rowing.