Kinematic comparisons of 1996 Olympic baseball pitchers

The aim of this study was to compare and evaluate the kinematics of baseball pitchers who participated in the 1996 XXVI Centennial Olympic Games. Two synchronized video cameras operating at 120 Hz were used to video 48 pitchers from Australia, Japan, the Netherlands, Cuba, Italy, Korea, Nicaragua and the USA. All pitchers were analysed while throwing the fastball pitch. Twenty-one kinematic parameters were measured at lead foot contact, during the arm cocking and arm acceleration phases, and at the instant of ball release. These parameters included stride length, foot angle and foot placement; shoulder abduction, shoulder horizontal adduction and shoulder external rotation; knee and elbow flexion; upper torso, shoulder internal rotation and elbow extension angular velocities; forward and lateral trunk tilt; and ball speed. A one-way analysis of variance (P ? 0.01) was used to assess kinematic differences. Shoulder horizontal adduction and shoulder external rotation at lead foot contact and ball speed at the instant of ball release were significantly different among countries. The greater shoulder horizontal abduction observed in Cuban pitchers at lead foot contact is thought to be an important factor in the generation of force throughout the arm cocking and arm acceleration phases, and may in part explain why Cuban pitchers generated the greatest ball release speed. We conclude that pitching kinematics are similar among baseball pitchers from different countries.     

利用离心向心训练法发展投掷运动员爆发力的实验研究

从肌肉不同收缩类型(离心收缩、向心收缩)的固有特性出发，在发展投掷运动员爆发力训练手段中，侧重安排了肌肉的离心收缩训练，经过9个月的训练实践，结果证明：这样的安排是可行的，有效的，运动员的各项素质指标及专项成绩均有显著性提高。     

Development of the Overarm Throw: Movement and Ball Velocity Changes by Seventh Grade

Abstract

Children studied longitudinally from kindergarten through second grade were refilmed in seventh grade as they performed 10 trials of the forceful overarm throw. The horizontal ball velocities of the 22 boys and the 17 girls were compared with predictions made when the children were in second grade. The original estimate of an annual rate of change (a “developmental year”) of 5–8 feet/sec/year (1.52–2.44m) remained accurate for the boys; the original estimate for the girls had to be increased to 2–4.5 feet/sec/year (.61–1.37m). While the gap between the sexes increased throughout elementary school, it increased at a slower rate from second to seventh grade than it had during the primary years. By seventh grade, however, the girls were 5 developmental years behind the boys. The data also suggested a difference in the degree to which the sexes maintained their relative positions within their groups: girls appeared more stable than boys across the elementary years. Change was also assessed in the developmental levels exhibited by the children as they threw. The girls' rate of development was 5–6 years behind the boys' rate. Few boys, however, had reached an advanced level in all movement components by seventh grade. Self-reports suggested that the boys had participated in more overarm throwing than had the girls.     

对我国优秀标枪运动员投掷步技术的研究

以国内外优秀标枪运动员为研究对象,通过国内外优秀标枪运动员投掷步技术参数的类比,从中找出我国优秀标枪运动员投掷步技术存在的差距,为促进我国标枪运动水平的提高提出方法。     

Forthcoming events

The proximal-to-distal segmental sequence has been identified in many sports activities, including baseball pitching and ball kicking. However, proximal-to-distal sequential muscle activity has not been identified. The aims of this study were to establish whether sequential muscle activity does occur and, if it does, to determine its functional role. We recorded surface electromyograms (EMGs) for 17 muscles from the upper extremity and abdomen during overarm throwing and detected the onset and peak times as indices of muscle activity. The following electromyographic properties were commonly identified in the participants. First, sequential muscle activity was observed from the scapular protractors to the shoulder horizontal flexors and from the shoulder horizontal flexors to the elbow extensor, but not from the elbow extensor to the wrist flexor or forearm pronator. Secondly, the external oblique contralateral to the throwing arm became activated before the ipsilateral external oblique. This sequence is considered to be very effective for the generation of high force and energy in the trunk. Thirdly, the ipsilateral external oblique began its activity almost at foot strike. Finally, the main activity of the rectus abdominis appeared just before the point of release.     

论运动训练原则在少年投掷训练中的运用

本研究针对当前存在的“早期专项化”、“拔苗助长”等少年田径运动员训练问题，通过回顾成材率较高的浙江省体育运动学校投掷组的训练，分析了黄志红、徐德妹、谢建华、戚莲芳、付丽敏、董晓红、李荣祥七位国际运动健将或运动健将（以后称“7T”）的少年期训练情况，从训练原则在实践中运用着手，探讨了“7T”在体校期间的训练指导思想，尤其是对系统不间断、全面与专项相结合、合理安排运动负荷这三个训练原则在“7T”少年期训练中的运用展开了讨论，并试图归纳、升华到理论的高度。     

《敦煌变文》中的“抛弃”义动词

《敦煌变文》的词汇很有特点，对于构建科学而系统的汉语词汇史有着重要意义。本文择取其中表“抛弃”义的五个动词加以探讨，通过共时与历时相结合的方法对该类动词进行考察，并在此基础上得出两个结论。     

投掷运动专项能力训练的功能因素分析

分析认为：为了提高投掷运动专项能力,应针对投掷运动中力的有序传递、力的非直线和非垂直方向性、稳固的左侧支撑、一次性爆发式用力、超越器械和超等长用力方式等功能因素进行训练。为了提高专项能力训练效果,还应树立以“强度”为核心的力量训练指导思想;还要注意科学地安排休息时间;关注运动技能的形成中枢神经系统参与的重要性。     

排球正面上手发球抛球技术的教学实验研究

对体育教育专业排球普修课正面上手发球的抛球采用不同方法的教学 实验,通过实验结果的比较与分析,提出了切实可行的正面上手发球的单手抛上旋 球方法,来提高正面上手发球效果。     

Radio-ulnar joint supinates around ball release during baseball fastball pitching

This study was conducted to determine whether a supination phase of the forearm exists around ball release (BRL), and, if present, to determine whether this supination is explained by a reaction force or by the body configuration required for this task. A 16-camera motion analysis system with a sampling frequency of 1,000 Hz recorded 20 healthy male semi-professional pitchers pitching from an indoor pitching mound. A short supination phase around BRL was confirmed for all participants in the current study. Correlation analyses revealed that the supination angle at BRL had significant relationships with several measurements of shoulder movement kinematics. Mechanical work analysis of the forearm’s longitudinal axis revealed several variations in joint power curve and various patterns of mechanical work among the participants, suggesting that a reaction force originating from accelerating a ball might not be the main cause of supination. The raw data also were down-sampled to a sampling frequency of 250 Hz, to match previous studies and to investigate the discrepancy among previous studies concerning the existence of the supination phase. The experience of participants and methodological differences, such as the definition of BRL and the time-normalisation technique, influenced whether the supination phase was observed.