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.     

Correlations between serum and salivary hormonal concentrations in response to resistance exercise

The aim of present study was to examine the relationships between serum and salivary values of free testosterone, dehydroepiandrosterone, and cortisol before and after a session of resistance exercise. Twenty-eight healthy men (mean age 40 years, s = 4) participated in the present study. Serum and salivary samples were collected at rest and after a multiple-sets resistance exercise protocol, of approximately 25 minutes duration. Concentrations of free testosterone, dehydroepiandrosterone, and cortisol were measured using radioimmunoassay kits. No significant correlation was observed between serum free testosterone and salivary testosterone (r = 0.22 to 0.26, P > 0.05). Serum cortisol was significantly correlated with salivary cortisol before (r = 0.52, P = 0.005) and after (r = 0.62, P = 0.001) the exercise protocol. Serum and salivary concentrations of dehydroepiandrosterone were significantly correlated before (r = 0.68, P < 0.001) and after (r = 0.7, P < 0.001) exercise. The results of the present study suggest that even under exercise conditions, the salivary values of cortisol and dehydroepiandrosterone can reflect the behaviour of these hormones in blood. However, further studies are necessary to verify if salivary testosterone reflects the behaviour of serum free testosterone during resistance exercise.     

Relationships among values, achievement orientations, and attitudes in youth sport

This research examines the value-expressive function of attitudes and achievement goal theory in predicting moral attitudes. In Study 1, the Youth Sport Values Questionnaire (YSVQ; Lee, Whitehead, & Balchin, 2000) was modified to measure moral, competence, and status values. In Study 2, structural equation modeling on data from 549 competitors (317 males, 232 females) aged 12-15 years showed that moral and competence values predicted prosocial attitudes, whereas moral (negatively) and status values (positively) predicted antisocial attitudes. Competence and status values predicted task and ego orientation, respectively, and task and ego orientation partially mediated the effect of competence values on prosocial attitudes and of status values on antisocial attitudes, respectively. The role of sport values is discussed, and new research directions are proposed.     

Self-presentational concerns and competitive anxiety

The purpose of this study was to improve understanding of the link between self-presentational concerns and competitive anxiety. Specifically, we examined (a) associations among self-presentational concerns and competitive state anxiety dimensional symptom responses using the modified Competitive State Anxiety Inventory-2 (CSAI-2; Martens, Vealey, & Burton, 1990) and (b) whether self-presentational concerns mediate trait-state anxiety relationships. In addressing these matters, we also examined the factor structure and composition of the Self-Presentation in Sport Questionnaire (SPSQ; Wilson & Eklund, 1998). Results showed that self-presentational concerns were positively associated with intensity and frequency dimensional symptoms and negatively associated with direction symptoms. Results also showed that self-presentational concerns demonstrated consistently higher associations with the cognitive component and the intensity symptom of the CSAI-2 state measures. Results showed no support for the notion that self-presentational concerns mediate the trait-state anxiety relationship. When examining the factor structure and composition of the SPSQ, the results from two independent athlete samples support the tenability of an abbreviated 21-item four-factor model. Thus the newly constituted scale is recommended for measuring self-presentational concerns in sport.     

Do achievement goals mediate stereotype threat?: an investigation on females' soccer performance

This research investigated stereotype threat effects on women's performance in sports and examined the mediation of this effect by achievement goals. The influence of two stereotypes-relative to the poor athletic ability and the poor technical soccer ability of women-were studied. Fifty-one female soccer players were randomly assigned to one of three conditions, introducing the task as diagnostic of athletic ability, technical soccer ability, or sports psychology. Next, they filled out a questionnaire measuring achievement goals and performed a soccer dribbling task. Results showed that compared with the control condition, females' performance significantly decreased in the athletic ability condition and tended to decrease in the technical soccer ability condition. Moreover, participants endorsed a performance-avoidance (relative to performance-approach) goal when the stereotypes were activated. However, this goal endorsement was not related to performance. The implications of these results for understanding the role of stereotypes in gender inequalities in sports are discussed.     

假如易建联没去密尔沃基

根据半个多月以来、全方面的问卷调查统计,针对＂如果给你一台多啦A梦的时间穿梭机,你最想回到什么时候？＂这一问题,得到的回答是：75 6%的学生想要回到童年的纯真时代;81.9%的已婚男性想要回到结婚之前的无烦恼时光;100%的成年女性想回到年轻20岁的少女时光;33.7%的无疾病老人安于现状,表示不想回到任何时间段;作为和我一起刚刚步入社会的上班族来说,最想时光倒流回到大学的浪漫时光。但是我想对于＂太空易＂来说,他最希望能回到2007年6月30日——2007年NBA选秀大会。     

基于Tobit模型的文化教育消费影响因素研究 ——以南昌市城乡居民调查为例

文化消费包括文化娱乐消费和文化教育消费,文化教育消费是其中非常重要的部分,对于提高居民总体消费水平、促进经济增长具有重要的意义.本文利用Tobit模型,结合南昌市城乡居民文化教育消费问卷调查的相关数据,实证得出:收入、教育供给、示范效应、社会保障等是影响文化教育消费重要因素的结论,并提出增加城乡居民家庭总收入、完善教育供给、发挥示范效应的作用、完善社会保障等政策建议.     

清末京师同文馆的第一位俄语教师

近年来,在学术界对於中俄关系史的研究不断增多,但是对於两国文化交流的研究还十分不足。本文讲述了清末北京的第一位俄语教师阿．弗．波波夫在外语学校“同文馆”的工作情况,以及他对於中国的记录。     

一次对流性强降水天气的成因分析

<正>本文利用常规观测资料、NCEP再分析资料以及多普勒雷达资料,对2016年7月6-7日南京中南部地区极端短时强降水天气进行分析,探讨了强降水产生的环境背景、有利条件以及雷达回波特征,以期为南京地区极端短时强降水的预报预警提供一些参考。地处长江中下游地区的南京,梅雨期间短时强降水天气的发生频率呈显著上升趋势,特别是雨强大于50 mm·h^-1的致灾性短时强降水天气过程发生次数呈显著增长^[1]。     

国家老年大学建设的理论逻辑与实践路径

国家老年大学建设是党中央、国务院围绕创新发展老年教育提出的一项重要顶层设计。文章从问题源流、政策源流和政治源流分析政策出台的背景,提出国家老年大学在制度系统、组织系统、课程系统、平台系统、服务系统等方面建设的实践路径,为国家老年大学的建设和发展提供借鉴和参考。