关于增强掷拨铅球力量的研究

铅球教学与训练,主要技术是持球,滑步,最后用力拨球和球出手后维持身体平衡几个部分,而用力掷拨球又是决定运动成绩好坏的关键。为提高上肢力量,在掷拨球教学中采用提拉式,上推式和吊球拨球法进行练习,不仅提高运动机能,而对提高身体素质,增加上肢肌群的爆发力量,有着重要作用。通过实践,实验对比,明显提高了运动成绩。该方法不仅适用教学,而且对训练也有指导价值,并具有一定的科学意义。     

The influence of the hand’s acceleration and the relative contribution of drag and lift forces in front crawl swimming

The aim of this study was to assess the effect of the hand’s acceleration on the propulsive forces and the relative contribution of the drag and lift on their resultant force in the separate phases of the front crawl underwater arm stroke. Ten female swimmers swam one trial of all-out 25-m front crawl. The underwater motion of each swimmer’s right hand was recorded using four camcorders and four periscope systems. Anatomical landmarks were digitised, and the propulsive forces generated by the swimmer’s hand were estimated from the kinematic data in conjunction with hydrodynamic coefficients. When the hand’s acceleration was taken into account, the magnitude of the propulsive forces was greater, with the exception of the mean drag force during the final part of the underwater arm stroke. The mean drag force was greater than the mean lift force in the middle part, while the mean lift force was greater than the mean drag force in the final part of the underwater arm stroke. Thus, swimmers should accelerate their hands from the beginning of their backward motion, press the water with large pitch angles during the middle part and sweep with small pitch angles during the final part of their underwater arm stroke.     

划水时手指张角的变化对游泳推进力影响的数值模拟

针对游泳中划水时手指应该张开与否的分歧,运用CFD数值模拟的方法,通过建立手掌和手指的简化模型,先后计算了手指分别张开不同角度及不同划水攻角时对应的阻力和阻力系数,计算结果表明手指张开角度越大其阻力和阻力系数越小。     

Scandinavian women’s football: the importance of male and female pioneers in the development of the sport

ABSTRACT

The importance of female and male pioneers in the development of women’s football in Scandinavia is in focus, where some of the female pioneers’ experiences presented. Sif Kalvø from Western Norway was the first known Scandinavian female football player who played abroad in Italy in 1971, and she was one of the pioneers. She was dependent on door openers in Norway and abroad. The door openers role, in making professional football possible; how the professional contracts came through; and why the Scandinavian female footballers went global in the early phases, discussed. To study this the Norwegian Mother of Women’s football, Målfrid Kuvås, and other female pioneer footballers are in-depth interviewed. Kuvås’ large collection of scrapbooks with media coverage, letters and other correspondence from the 1960s to 2000s are also studied. Qualitative in-depth interviews carried out, with five of the early professionals and five of the leaders involved in the migration processes. Secondary sources are academic literature and sport media. The dream about playing professional football, and to be able to live from football brought female players across the globe. Due to this, migration research is of interest when studying women’s football, and ‘push’- and ‘pull’- factors in migration are discussed.     

沉着“泳”对

从为什么会沉,怎样抑制沉,以及如何利用沉三个维度运用文献资料、实验对比等研究方法分析了人体在水中的沉浮现象。本着理论指导实践角度出发,从人体成分、与水的密度关系、浮力以及重浮心角度阐述了游泳过程中的下沉现象符合自然现象和科学规律。让学员从身体和心理角度冷静、沉着面对游泳时的沉、浮现象;正确、勇于、敢于接受下沉事实,让轻松游泳伴随你我。     

Letter to the editor concerning the article “Bar velocities capable of optimising the muscle power in strength-power exercises” by Loturco,Pereira, Abad,Tabares, Moraes,Kobal, Kitamura & Nakamura (2017)

Loturco and co-workers (2017) recently published data in the Journal of Sports Sciences to present the optimum loading magnitudes regarding the maximization of the “mean propulsive power” of the leg and arm muscles. Among the most important findings were that (1) the recorded power in the squat and squat jump exercises was markedly low, (2) the optimum external load that maximized the power in the same exercises was close to 100% of body weight, while (3) the ballistic bench press throw revealed smaller power than the regular bench press typically performed with relatively low level of muscle activation towards the end of the propulsive lifting phase. The findings are either counter-intuitive, or contradict the literature findings, or both, and we believe that they originate from apparent methodological flaws. The first one is neglecting the force acting against the body segments moved together with the external load that is particularly high in squat exercises. The second one is an erroneous calculation of the propulsive phase that included a part of the bar’s flight time. Both of these methodological flaws are frequent in the literature and could be associated with the improper use and calculation of variables when utilizing linear position transducers.     

The suitability of Sanders’ model for calculation of the propulsive force generated by the hands during sculling motion

This study examined whether Sanders’ model is suitable for estimating accurately the propulsive force generated by the hands’ motion in swimming comparing the calculated force obtained using the model and the measured force during an actual propulsive action. The measured and calculated forces were obtained from 13 swimmers who, while tethered, performed a sculling motion in a prone position for the purpose of displacing the body by moving it forward. Kinematic analyses were conducted to obtain the calculated force, while the measured force was obtained via the use of a load cell. The calculated force was lower than the measured force and accounted for only a small part of the variation in the measured force. The forces could not be used interchangeably, and there were fixed and proportional differences between them. Consequently, this study indicates that Sanders’ model is not suitable for estimating accurately the propulsive force generated by the swimmer’s hands during sculling motion. However, research that integrates analyses from different approaches could result in improvements to the model that would render it applicable for estimating the propulsive forces during movements that are characterised by directional changes of the hands.     

对我国优秀男子跳远运动员劳剑峰起跳技术的生物力学分析

对劳剑峰九运会决赛最佳跳次的技术录像进行解析,结合专项理论并与国外优秀运动员的技术统计数据对比,得出: 1. 适宜增加起跳阶段的水平速度损失率,从而加大腾起角度,使起跳离地瞬间的水平速度和垂直速度的匹配更加合理,是改善起跳效果和提高成绩的重要途径.2. 改善起跳阶段的技术,减小着地脚和起跳阶段的扇面角,增大离地角是技术改进的方向.3. 加强膝关节快速用力条件下的退让式收缩能力和克制性收缩力量是专项力量训练的重点.     

超等长阻力训练对下肢各关节角动力学的影响

为测试超等长阻力训练前后原地垂直纵跳动作下肢各关节角速度及角加速度,计算下肢各关节角刚度,观察超等长阻力训练对下肢各关节角动力学的影响。将16名青年男子篮球运动员随机分成超等长阻力训练组和常规训练对照组。采用VICON和三维测力台采集每个动作的运动学和动力学数据,计算下肢各关节角速度及角加速度,并经逆动力学方法计算下肢净关节力矩。结果可见,超等长阻力训练组髋、踝关节角速度和角刚度明显高于对照组,膝关节角速度及角刚度两组没有明显差异;超等长阻力训练组髋、膝、踝关节角加速度均显著高于对照组。结果说明超等长阻力训练可降低拉长-缩短周期支撑时间、缩短摊还期、增强肌肉-肌腱复合体能量转换能力、提高下肢肌肉爆发力。适于需要关节角速度、角加速度及爆发力的项目。     

Analysis of Stroke Organization in the Backstroke as a Function of Skill

Abstract

This study investigated the effects of three different amounts of practice in combination with two types of variable practice conditions upon schema development. Seventy-two subjects were administered either 6, 18, or 36 trials while learning to move to either one- or three-criteria goals on the linear positioning task. Subjects then had 18 no-KR (knowledge of results) trials to produce a novel response. The statistical analysis revealed a significant three-way interaction for absolute error while no significant main or interaction effects existed for constant or variable error. Analysis of the simple main effects showed that the various amounts of practice produced similar performances for the subjects learning to move to only one criterion goal. For the subjects learning to move to three criteria goals during initial practice, the amount of practice provided was a significant factor in the accuracy and strength of the motor schema. Partial support is presented for schema theory.     

男子跳远运动员不同跳次中摆动腿摆动对速度变化特征的影响

采用现场定点高速摄像及数理统计法，对男子跳远运动员起跳阶段不同时相、身体重心水平速度和垂直速度的变化与起跳缓冲、蹬伸阶段摆动腿角速度和两大腿夹角变化进行比较分析。结果表明：成绩较好者，缓冲阶段身体重心水平速度减小值略大，垂直速度的增加值则更大；离板瞬间身体重心水平速度和垂直速度都呈现出相对较大的趋势。     

影响短跑运动员运动成绩的要因

通过等动测力系统对短跑运动员在角速度为60°/s、180°/s及300°/s的膝关节和髋关节伸、屈肌峰力矩进行了测试,并就测试结果与不同距离短跑成绩之间的相关性进行了探讨,发现不同角速度的伸肌峰力矩均明显高于屈肌峰力矩,同时也发现100m加速跑成绩相关最显著的是角速度为300°/s时膝关节伸肌力矩和180°/s时髋关节伸肌力矩.     

不同角速度下自行车运动员髋关节肌群等速向心收缩的肌力研究

利用Con-Trex等速肌力测试与训练系统,以180°/s、120°/s、60°/s的3种角速度对13名男子优秀自行车运动员和13名女子优秀自行车运动员左腿髋关节进行等速向心收缩测试。获得了相应的等速向心收缩的伸屈肌峰值力矩、伸屈肌总功、伸屈肌平均功率等指标,并结合项目特点分析各角速度下指标的差异。     

Comparison of two methodological approaches for the mechanical analysis of single-joint isoinertial movement using a customised isokinetic dynamometer*

Compared to isokinetic and isometric tests, isoinertial movements have been poorly used to assess single-joint performance. Two calculation procedures were developed to estimate mechanical performance during single-joint isoinertial movements performed on a customised isokinetic dynamometer. The results were also compared to appreciate the effects of measurement systems and calculation procedures. Five participants performed maximal knee extensions at four levels of resistance (30, 50, 70 and 90% of the one-repetition maximum, 1-RM). Joint angular velocity and torque were assessed from customised isokinetic dynamometer measures (method A) and from weight stack kinematic (method B). Bland–Altman plots and mean percent differences (M_diff) were used to assess the level of agreement for mean and peak angular velocity and torque. A Passing–Bablok regression was performed to compare the angular velocity-angle and torque-angle relationships computed from the two analysis methods. The results showed a high level of agreement for all mechanical parameters (M_diff < 6% for all parameters). No statistically significant differences were observed between methods A and B in terms of angular velocity-angle and torque-angle relationships except at 30% of 1-RM for the torque-angle relationship. Both methodologies provide comparable values of angular velocity and torque, offering alternative approaches to assess neuromuscular function from single-joint isoinertial movements.     

Knee joint coordination during single-leg landing in different directions

ABSTRACT

Knee joint coordination during jump landing in different directions is an important consideration for injury prevention. The aim of the current study was to investigate knee and hip kinematics on the non-dominant and dominant limbs during landing. A total of 19 female volleyball athletes performed single-leg jump-landing tests in four directions; forward (0°), diagonal (30° and 60°) and lateral (90°) directions. Kinematic and ground reaction force data were collected using a 10-camera Vicon system and an AMTI force plate. Knee and hip joint angles, and knee angular velocities were calculated using a lower extremity model in Visual3D. A two factor repeated measures ANOVA was performed to explore limb dominance and jump direction. Significant differences were seen between the jump directions for; angular velocity at initial contact (p < 0.001), angular velocity at peak vertical ground reaction force (p < 0.001), and knee flexion excursion (p = 0.016). Knee coordination was observed to be poorer in the early phase of velocity-angle plot during landing in lateral direction compared to forward and diagonal directions. The non-dominant limb seemed to have better coordination than the dominant limb during multi-direction jump landing. Therefore, dominant limbs appear to be at a higher injury risk than non-dominant limbs.