Electrical and mechanical response of skeletal muscle to electrical stimulation after acute passive stretching in humans: a combined electromyographic and mechanomyographic approach

Two mechanisms have been suggested to explain stretching-induced maximum force depression: a mechanical alteration in the stretched muscle and an impairment of neural activation. Electrical stimulation allows standardization of the level of muscle activation without being limited by neural control. The aim of this study was to evaluate the stretching-induced changes in the electrical and mechanical properties of muscle during electrically elicited contractions. Twelve participants (age 22 +/- 1 years; body mass 75 +/- 2 kg; stature 1.79 +/- 0.02 m; mean +/- standard error) underwent six electrical stimulations of the medial gastrocnemius muscle before and after stretching. During the contractions, surface electromyogram (EMG) and mechanomyogram (MMG) were recorded simultaneously together with force. After stretching we found: (i) no differences in EMG parameters; (ii) MMG amplitude decreased by 4 +/- 1% (P < 0.05); and (iii) the peak force, the peak rate of force development, and the acceleration peak of force development decreased by 12 +/- 3%, 14 +/- 1%, and 24 +/- 5%, respectively (P < 0.05). In conclusion, acute passive stretching did not change EMG properties but altered the mechanical characteristics of the contracting muscle. Indeed, muscle force-generating capacity and stiffness of the muscle-tendon unit were significantly impaired.     

But I like PE: factors associated with enjoyment of physical education class in middle school girls

The current study examined associations between physical education (PE) class enjoyment and sociodemographic, personal, and perceived school environment factors among early adolescent girls. Participants included 1,511 sixth-grade girls who completed baseline assessments for the Trial of Activity in Adolescent Girls, with 50% indicating they enjoyed PE class a lot. Variables positively associated with PE class enjoyment included physical activity level, perceived benefits of physical activity, self-efficacy for leisure time physical activity, and perceived school climate for girls' physical activity as influenced by teachers, while body mass index was inversely associated with PE class enjoyment. After adjusting for all variables in the model, PE class enjoyment was significantly greater in Blacks than in Whites. In model testing, with mutual adjustment for all variables, self-efficacy was the strongest correlate of PE class enjoyment, followed by perceived benefits, race/ethnicity, and teachers' support for girls' physical activity, as compared to boys, at school. The overall model explained 11% of the variance in PE class enjoyment. Findings suggest that efforts to enhance girls' self-efficacy and perceived benefits and to provide a supportive PE class environment that promotes gender equality can potentially increase PE class enjoyment among young girls.     

Contextual influences on baseball ball-strike decisions in umpires, players, and controls

Baseball umpires, players, and control participants with no baseball experience were asked to call balls and strikes for video clips. In a basic judgement task, umpires and players were significantly better at calling pitches than controls. In a direct information task, borderline pitches were presented following clips of definite balls and definite strikes. Participants called target pitches closer to the strike end of the scale when viewed after definite balls than when they followed definite strikes. Similarly, when borderline pitches were shown in different pitch counts, participants called pitches more towards the strike end of the scale when there were three balls in the count (3-0, 3-2). These findings indicate that the standard for evaluation changes based on the context in which stimuli are processed. Moreover, the strength of the contextual factors is illustrated in that the effects were shown in observers with and without experience in the task. Overall, however, umpires had a greater tendency to call strikes, indicating that they may use a norm of "hastening the game".     

On the temporal and behavioural consistency of pre-performance routines: an intra-individual analysis of elite basketball players' free throw shooting accuracy

The effectiveness of pre-performance routines on skilled performance in a self-paced skill has yet to be verified. In this study, we examine the importance of temporal and behavioural consistency in these routines. The duration and specific pattern of behaviours exhibited before each free throw (n = 284) were observed during 14 National Basketball Association play-off games. An intra-individual standardized score was calculated for each shot's duration. Each player's dominant behavioural routine was identified and each shot was classified as "sequence followed" or "sequence not followed". No difference was observed in the success rates of shots associated with brief, long, and regular duration routines (P > 0.05). However, players were more successful when they followed their dominant behavioural sequence (83.77% success) than when they deviated from their specific behavioural pattern (71.43% success) (P < 0.05). The findings are interpreted in light of relevant theory and implications for practice are discussed.     

Game management, context effects, and calibration: the case of yellow cards in soccer

Referees in German first-league soccer games do not award as many yellow cards in the beginning of a game as should be statistically expected. One explanation for this effect is the concept of game management (Mascarenhas, Collins, & Mortimer, 2002). Alternatively, the consistency model (Haubensak, 1992) explains the effect as a necessity of the judgment situation: Referees need to calibrate a judgment scale, and, to preserve degrees of freedom in that scale, they need to avoid extreme category judgments in the beginning (i.e., yellow cards). Experiment 1 shows that referees who judge scenes in the context of a game award fewer yellow cards than referees who see the same scenes in random order. Experiment 2 shows the combined influence of game management (by explicitly providing information about the game situation) and calibration (early vs. late scenes in the time course of a game). Theoretical implications for expert refereeing and referee training are discussed.     

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.     

铜合金藏品保护的一种新方法

这是一种去除青铜病保护古代铜器和铜合金物品的新方法。有机化合物2—胺基—5—巯基—1,3,4—噻重氮是优良的铜器缓蚀剂,它可以完全除去青铜病,并在金属表面形成一层保护性的多聚络合物,防止腐蚀继续发展。     

利用心率测定无氧阈

本文以自行车运动员为研究对象,在现场采用定量增加车速的方法来研究运动员心率随车速变化的规律。发现在达到某一负荷速度之前,运动员的心率与车速的增加呈直线相关,而在这种负荷速度之后,上述直线关系明显地发生变化。这种现象在其他竞速运动项目中也被重复,所以称这个速度为偏转速度。偏转速度出现的时间恰与运动员体内血乳酸开始大量堆积的时间相吻合,故作者认为可以利用偏转速度的测定来确定运动员的无氧阈。     

鲍士伟与中国图书馆的发展:国际合作的一个篇章

本世纪20年代,美国图书馆学家鲍士伟先生对中国进行了短暂的七周考察,旨在鼓动公共资金对中国发展公共图书馆事业的投资。这一事件构成了当时中美图书馆界一大“热点”。本文就是遵循这一历史事实,探索中国图书馆当时所处的大环境、鲍先生访问背景和相关的人物,及其对这一创举所具备的短期和长远影响进行客观评价。