Kinematic and kinetic comparisons between American and Korean professional baseball pitchers

The purpose of this study was to quantify and compare kinematic, temporal, and kinetic characteristics of American and Korean professional pitchers in order to investigate differences in pitching mechanics, performance, and injury risks among two different cultures and populations of baseball pitchers. Eleven American and eight Korean healthy professional baseball pitchers threw multiple fastball pitches off an indoor throwing mound positioned at regulation distance from home plate. A Motion Analysis three-dimensional automatic digitizing system was used to collect 200 Hz video data from four electronically synchronized cameras. Twenty kinematic, six temporal, and 11 kinetic variables were analyzed at lead foot contact, during the arm cocking and arm acceleration phases, at ball release, and during the arm deceleration phase. A radar gun was used to quantify ball velocity. At lead foot contact, the American pitchers had significantly greater horizontal abduction of the throwing shoulder, while Korean pitchers exhibited significantly greater abduction and external rotation of the throwing shoulder. During arm cocking, the American pitchers displayed significantly greater maximum shoulder external rotation and maximum pelvis angular velocity. At the instant of ball release, the American pitchers had significantly greater forward trunk tilt and ball velocity and significantly less knee flexion, which help explain why the American pitchers had 10% greater ball velocity compared to the Korean pitchers. The American pitchers had significantly greater maximum shoulder internal rotation torque and maximum elbow varus torque during arm cocking, significantly greater elbow flexion torque during arm acceleration, and significantly greater shoulder and elbow proximal forces during arm deceleration. While greater shoulder and elbow forces and torques generated in the American pitchers helped generate greater ball velocity for the American group, these greater kinetics may predispose this group to a higher risk of shoulder and elbow injuries.     

中非论坛“惹火”非洲游

随着中非论坛在京成功召开，整个北京乃至全国正在掀起一股强烈的“非洲热”。非洲大陆自然、原始的景观，热情、纯朴的民风，神秘、悠久的历史以及丰富、独特的动植物资源更令许多人心驰神往……于是，去非洲旅游，就成为旅朋友境外游的首选地。[编者按]     

群居部落的别样生活

摄影QQ群，媒体人QQ群、DJ美女家庭……网络世界里的“群势力”正在我们的生活中蔓延，他们在网络与现实世界里交替游走，建立起一种新型的社交生活方式，浪漫携手、郊游爬山、体育锻炼、美食FB、聚众K歌、宠物比拼、商务交流、公益活动等，构成了现代都市又一道别致的风景——都市丛森群居部落的别样生活。[编者按]     

游泳运动员的柔韧性训练

美国游泳专家埃米利·萨威纳和泰里·马隆专著指出,“柔韧性可归纳为关节灵活性的范畴。发展柔韧性的准则取决于运动项目。肩关节和踝关节柔韧性在很大程度上对游泳提供出色的成绩起着决定性的因素”。 在训练时,时间的因素显得格外重要。最理想     

工业和商业预测方法(指数平滑法和曲线拟合法实用指南)

工业和商业预测方法从实用的角度系统地介绍了确定型时间序列分析模型和回归模型。其中第一篇着重讨论各种时序模型的特点及其应用,并给出了相应的工作流程图,具有很大的参考价值。我们将分两次在增刊上刊载全文,本次刊载的是时序预测部分。     

基本的情报测度

情报与决策活动是密切相关的,情报减少决策中的不确定性。在效果意义上,不确定性应与决策者对行动方案的选择有关,而选择行动方案过程中的不确定性明显地与决策者执行每个方案的概率P有关。如果所有的P都相同,那么决策者便完全不能确定选择那个方案;如果决策者已确定了他的行动方案,那么,对某一i来说,P(αi)=1,而其它的概率为0。所以我们选用概率P的方差作为情报测度的主要成份。当P都相同时,方差为0,当某一P为1而其它的P为0时,方差最大。     

Associations between academic and motor performance in a heterogeneous sample of children with learning disabilities

A heterogeneous sample of 137 school-aged children with learning disabilities (IQ > 80) attending special needs schools was examined on the Movement Assessment Battery for Children (MABC). The results show that compared to the available norm scores, 52.6% of the children tested performed below the 15th percentile on manual dexterity, 40.9% on ball skills, and 33.7% on balance skills. Furthermore, after controlling for IQ, significant small to moderate partial correlations were found between spelling and mathematics and the MABC total score, as well as small to moderate correlations between mathematics and balance, between reading and ball skills, and between spelling and manual dexterity. The present findings are compared with previously reported results obtained in more homogenous groups, and based on the resultant relationships between academic performance and motor development, recommendations for future motor intervention studies are made.