Validation of an integrated experimental set-up for kinetic and kinematic three-dimensional analyses in a training environment

Biomechanical analyses using synchronized tools [electromyography (EMG), motion capture, force sensors, force platform, and digital camera] are classically performed in a laboratory environment that could influence the performance. We present a system for studying the running sprint start that synchronizes motion capture, EMG, and ground reaction force data. To maximize motion capture (Vicon 612 with six cameras), a special dim environment was created in the stadium. "Classical" tools were combined with "purpose-built" tools intended to analyse the different aspects of movement. For example, a synchronization system was built to create a common time-base for all data recordings and a portable EMG system was synchronized by a cable that was "disconnected" by the athlete's movement out of the blocks. This disconnection represented an independent event recorded by different tools. A "gap" was measured for some sprint start events between kinetic and kinematic (motion capture) data. Calibration results, measurements of time "gap", and duration of the independent event were used to validate the accuracy of motion capture and the synchronization system. The results validate the entire experimental set-up and suggest adjustment values for motion capture data. This environment can be used to study other movements and can easily be applied to several sports.     

Elite football on artificial turf versus natural grass: movement patterns, technical standards, and player impressions

The aim of the present study was to examine the movement patterns, ball skills, and the impressions of Swedish elite football players during competitive games on artificial turf and natural grass. Time - motion analyses (36 observations) and technical analyses (16 team observations) were performed and 72 male and 21 female players completed a questionnaire. No differences were observed between artificial turf and natural grass in terms of total distance covered (mean 10.19 km, s = 0.19 vs. 10.33 km, s = 0.23), high-intensity running (1.86 km, s = 0.10 vs. 1.87 km, s = 0.14), number of sprints (21, s = 1 vs. 22, s = 2), standing tackles (10, s = 1 vs. 11, s = 1) or headers per game (8, s = 1 vs. 8, s = 1), whereas there were fewer sliding tackles (P < 0.05) on artificial turf than natural grass (2.1, s = 0.5 vs. 4.3, s = 0.6). There were more short passes (218, s = 14 vs. 167, s = 12) and midfield-to-midfield passes (148, s = 11 vs. 107, s = 8) (both P < 0.05) on artificial turf than natural grass. On a scale of 0-10, where 0 = "better than", 5 = "equal to", and 10 = "worse than", the male players reported a negative overall impression (8.3, s = 0.2), poorer ball control (7.3, s = 0.3), and greater physical effort (7.2, s = 0.2) on artificial turf than natural grass. In conclusion, the running activities and technical standard were similar during games on artificial turf and natural grass. However, fewer sliding tackles and more short passes were performed during games on artificial turf. The observed change in playing style could partly explain the male players' negative impression of artificial turf.     

Energy balance of locomotion with pedal-driven watercraft

In this study, we examined the mechanics and energetics of locomotion with a paddle-wheel boat and a water bike. Power output (Wtot) was measured directly on the water bike by means of an instrumented chain-ring. The simultaneous assessment of oxygen uptake (VO2) allowed the computation of the "overall" efficiency of locomotion (etao = Wtot/VO2). Mean etao was 0.27 (s = 0.02), which was unaffected by the speed, and was assumed to be the same for the two boats as both are semi-recumbent bicycles. For the paddle-wheel boat, Wtot was then obtained from etao and measures of VO2. The power to overcome (passive) drag was calculated as Wd = D x v (where D is the force measured by means of a load cell when towing the boats at given speeds). Propelling efficiency was calculated as etap = Wd/Wtot, which was lower with the paddle-wheel boat (mean 0.35, s = 0.01) than with the water bike (mean 0.57, s = 0.01). The observed differences in etap and Wd explain why at the highest speed tested (approximately 3 m s(-1), the energy required to cover a unit distance with the water bike is similar to that required to move the paddle-wheel boat at 1.3 m s-1).     

GaIN (Georgia Interactive Network for Medical Information) study on health professionals' search requests and continuing education needs

Health sciences librarians are being called upon to be more proactive in their institutions' continuing education efforts. In an effort to identify whether search requests indicated CE needs, a study was conducted by a group of members of GaIN (Georgia Interactive Network for Medical Information). MEDLINE requests from health care professionals for subject specific clinical topics were collected during a six-month period via a standard search request form created for the study. Copies of all completed requests were collected and broad ICD-9 codes assigned to the search topics. Institutional reports were generated for each participating library to share with hospital CE coordinators. They were also compiled for the group as a whole, and reflected the "hottest" topics requested during the study period for physicians and for non-physicians (nurses, allied health, administrators). A survey to hospital librarians and CE educators showed some value in the reports, but greater potential for further collaboration between librarians and CE coordinators.     

哈特私通事件

1987年5月,竞选英国民主党总统候选人的加里·哈特由于新闻界披露了他的桃色新闻而退出竞选,这件事震动了美国朝野,在新闻界也引起了一场争论。争论涉及到新闻媒介的权利、责任与职业道德,新闻的真实性等方面的问题。这里编译的是美国《哥伦比亚新闻学评论》杂志最近的有关评论文章,剖析了新闻界在哈特事件中所起的作用,反映了美国新闻界一部分人的看法。     

л·康德娜季耶娃的起跑技术

在奥运会的预赛中,康德娜季耶娃战胜了哈格吕德(瑞典)、X·汉特(英国),并跑出了11″13的好成绩。康德娜季耶娃的起跑有什么样的特点呢? 在《预备》口令后,运动员采用“中间式”安装起跑器的方法,肩很容易过起跑线,身体重量均匀地分布在手臂和腿上。运动员的头放松低下,目视跑道,这表示颈部肌肉处于放松的位置。这在起跑的技术中,是一个重要的因素。因为,颈部肌肉紧张,通常将引起起跑后的第一步     

The stress of travel

International travel is an essential part of the life of elite athletes, both for competition and training. It is also becoming increasingly common among recreational sportspersons. Long-distance travel is associated with a group of transient negative effects, collectively referred to as 'travel fatigue', which result from anxiety about the journey, the change to an individual's daily routine, and dehydration due to time spent in the dry air of the aircraft cabin. Travel fatigue lasts for only a day or so, but for those who fly across several time zones, there are also the longer-lasting difficulties associated with 'jet lag'. The problems of jet lag can last for over a week if the flight crosses 10 time zones or more, and they can reduce performance and the motivation to train effectively. Knowledge of the properties of the body clock enables the cause of the difficulties to be understood (an unadjusted body clock), and forms the basis of using light in the new time zone to promote adjustment of the body clock. Sleep loss and its effects are important components of jet lag, and attempts to promote sleep by the use of melatonin and other hypnotics are also relevant. Sleep loss is also found in those who undertake challenges that involve long periods where the normal consolidated sleep of 8 h length is not possible. Advice on sleep regimens in such circumstances is given.     

提高助跑的准确性

我们的跳远和三级跳远运动员年年都提高了运动成绩,从而走在世界优秀运动员的最前列.但是,他们迄今仍然存在着助跑准确性差这一缺点.捷尔——奥尔涅祥和戈利稚夫在去年的比赛季节中,脚踏板过线的错误占全部跳跃的30-50%.费多谢耶夫和加列也尔也常犯踏板过线或过早起跳的错误.利稚霍夫斯基当助跑不准确时,就会降低成绩20——30厘米.在最优秀运动员当中,助跑较准确的一些的,只有沙波鲁谱娅和波达连柯两人.至于其余的许多运动员的助跑也往往缺乏稳定的准确性.对不准确的助跑进行分析的结果表明,在训练实践中,我们没有采用有效的方法,来帮助运动员把动     

少年篮球运动员在准备参加比赛期的训练安排

不断完善少年篮球运动员的训练体系,是广大教练员和科学工作者经常注意的研究课题。多数研究的主要问题有:教学方法;一定的训练方案对身体训练的影响;通过教育观察论证教学方法;等等。也有一些牵涉到少年篮球运动员训练安排的文章,但是为数很少。本文的任务是:研究我们制定的少年