Optimizing segmental movement in the jumping header in soccer

This study looks at segmental movements in the jumping header from an optimization viewpoint. Investigations on the header so far have focused on head restriction in the movement but have not clarified how and to what extent body segments influence the performance of the skill. In the present study a biomechanical model was used to analyze the jumping header in simulated competition to give a clear picture of an optimized header. Skilled soccer players headed balls at speeds of 13 m x s(-1) the results indicated that the head moves as a free non-restricted segment in the jumping header and should be allowed to do so, even though much soccer literature says otherwise to prevent injuries. The arm movement showed individual characteristics and gave no general advantages in optimizing ball speed after impact in the header The movement of the legs was, on the other hand, the single most important factor in the skill. Therefore, coaches and players shouldfocus on developing muscle strength in the stomach, back and pelvis and should put no restrictions on head and arm movement to optimize the jumping header.     

力量素质和决定力量素质的诸因素

沃罗比耶夫是苏联原国家举重队总教练,医学副博士,本人亦曾经多次创造90公斤级举重世界纪录。他在1977年所著《举重运动的生理学与训练》一书,系统地总结了苏联优秀举重运动员的训练经验,并使之与运动生物力学、运动生理学、运动医学紧密结合,融为一体。该书资料丰富,数椐处理严格、论据明确,科学性强。对我国举重教练员、运动员、运动医生有较大参考价值。由于时隔五年,个别论述已失之陈旧。本刊拟摘其精华,编译登载。本期刊登的是该书第二章“力量素质和决定力量素质的各种因素”的主要内容,以后将陆续编译刊登其它部分。     

Sequential muscle activity and its functional role in the upper extremity and trunk during overarm throwing

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.     

甜蜜的家庭

~~甜蜜的家庭@John H.Payne @张梦华     

电视屏幕上的综艺“明星”

是否存在着电视综艺“明星”的“特点呢?初看起来,这个问题显得那么浅显,答案义可能会显得那么简单。其实舞台上的综艺“明星”与电视屏幕上的综艺“叫星”还是有区别的!综艺“明星”同任何一个演员一样,在     

美国新闻与大众传播研究

引言正如鱼在的世界里全然感觉不到水的存在一样,美国学术界直到不久以前也基本上忽视了新闻学的存在。虽然我们宪法的制订者们曾认真思考过新闻事业在民主社会中的作用,虽然从历史上看许多新闻工作者也凭经验进行探索,并取得了许多对现化学术研究极为有用的成果,但是,人们至今用传统的学究式的清规戒律衡量新闻工作者。不过,人们从实用主义的角度出发,对如何通过新闻宣传来贏得战争胜利的问题和如何吸引大量受众接收20世纪大传媒公司节目的问题的关注,以及对传播内容短期社会效果问