The core musculature in male prepubescent tennis players and untrained counterparts: a volumetric MRI study

The effects of exercise on the core musculature have not been investigated in prepubescents. The main purpose of the present study was to determine the volume and degree of asymmetry of rectus abdominis, obliques and transversus abdominis, quadratus lumborum, iliopsoas, gluteus and paravertebralis muscles in prepubescent tennis players and in untrained boys. The muscle volume was determined using magnetic resonance imaging (MRI) in 7 male prepubescent tennis players and 10 untrained controls (mean age 11.0 ± 0.8 years, Tanner 1–2). After accounting for height and body weight as covariates, the tennis players had 14–34% greater volume than the controls in all the muscles analysed (P < 0.05) except in paravertebralis, dominant quadratus lumborum and non-dominant gluteus, which had similar volumes in both groups (P = NS). Compared to controls, the tennis players displayed a greater degree of asymmetry in quadratus lumborum and rectus abdominis (3% vs. 15%, P < 0.01 and 8% vs. 17%, P = 0.06, respectively). The level of asymmetry of obliques and transversus abdominis, iliopsoas, gluteus and paravertebralis muscles was similar in both groups (P = NS). In conclusion, tennis playing at prepubertal ages induces a selective hypertrophy of the core musculature and exaggerates the degree of asymmetry of quadratus lumborum and rectus abdominis compared to untrained boys.     

Allocation of time in self-paced memory tasks: the role of practice, instructions, and individual differences in optimizing performance

Nelson & Narens (1990) proposed that the allocation of study time in self-paced memory tasks depends on the comparison between the norm of study (established before studying) and the level of learning reached. We explored the role of practice, instructions, and individual differences in determining the norm of study and optimizing performance. In Study 1, participants carried out various study trials involving different (but similar) lists of words. In Study 2, participants were instructed to attain either maximum recall or maximum speed. In Study 3, the study time spontaneously used by each participant was estimated. The effect of increasing or decreasing this time was observed. Memory span and speed of lexical processing were also measured. Finally, Study 4 estimated participants were able to adapt performance to objective criteria (e.g., instructions). However, the time that they spontaneously use tends to be the most efficient. Variations in these times lead to losses in efficiency. Differences in processing capacity or motivation seem not to determine the differences in study time.     

对葡萄牙年轻乒乓球运动员训练结构的研究

从乒乓球国际比赛的情况看,近两年来葡萄牙乒乓球运动员人数显著增加,并且技术水平也明显提高.1996年在巴黎举行的欧洲青年乒乓球锦标赛上,葡萄牙运动员在乒乓球运动史上首次拿到了一枚个人项目的铜牌,实现历史性的突破.从这以后,葡萄牙运动员又多次在国际乒乓球赛事上获得奖牌.然而,如果以20世纪90年代或21世纪初期的情况作参照,不难看出,年轻运动员的技术水平要达到具有取得这样成绩的技术水平还相差得很远.因而,本文在深入调查和了解葡萄牙乒乓球联合会各训练中心年轻乒乓球运动员的训练结构基础上,分析这些训练方式方法是否促进这些年轻运动员协调、快速发展,并在成年时代达到最佳运动技术水平.研究方法本文通过对葡萄牙乒乓球联合会3个训练中心2002至2003年赛季的训练工作的记录文件进行整理,采用文献资料法、调查法、统计法、对比分析的方法进行了研究.主要结果研究分析可知,要使这些年轻运动员在成年时代达到顶尖级水平,这些训练量是不够的;教练员在给运动员的训练安排中主要以技术训练、战术训练和身体素质训练为主,并把重点放在了技、战术的结合方面,其结果还表明运动员在心理因素的训练方面极为不足.另外,在技术、战术、身体素质以及心理训练等各子项的具体内容安排方面也与现代乒乓球运动所要求的特点不相符合.     

Evaluating hierarchical organisation structures for exploring digital libraries

Search boxes providing simple keyword-based search are insufficient when users have complex information needs or are unfamiliar with a collection, for example in large digital libraries. Browsing hierarchies can support these richer interactions, but many collections do not have a suitable hierarchy available. In this paper we present a number of approaches for automatically creating hierarchies and mapping items into them, including a novel technique which automatically adapts a Wikipedia-based taxonomy to the target collection. These approaches are applied to a large collection of cultural heritage items which is formed through the aggregation of other collections and for which no unified hierarchy is available. We investigate a number of novel user-evaluated metrics to quantify the hierarchies’ quality and performance, showing that the proposed technique is preferred by users. From this we draw a number of conclusions as to what makes a hierarchy useful to the user.     

School Schedules Affect Sleep Timing in Children and Contribute to Partial Sleep Deprivation

Although the environmental light/dark cycle is the main zeitgeber for the human species, the social cues seem to be important in the synchronization of circadian rhythms. In Brazil, the existence of two school schedules—one with only morning classes (MG) and other with only afternoon classes (AG)—allows the investigation of the effect of school activities on light exposure and sleep/wake patterns in children. Forty‐seven children wore wrist actimeters for a week for registration of light and sleep data. MG children presented shorter sleep duration on school days than the children from the AG. The results showed that during school days MG children were exposed to bright light earlier in the morning when compared to AG children. Nevertheless, there were no differences in light exposure after sunset. The results reflect the role of school schedules and artificial light in shaping light exposure, and its association with sleep timing in children.     

Identifying the information management process and knowledge creation in technology-based companies: a Brazilian comparative case study

Knowledge Management Research & Practice - Information and knowledge have been cited over the last two decades as competitive advantage tools. Recently, the use of them has been discussed to...     

Food for Education in Honduras: Psychosocial correlates of childhood literacy

School feeding programs in low- and middle-income countries tend to focus on school attendance and literacy. Some evidence suggests that bolstering schools as a nexus of community plays an important psychosocial function for children and families. This study examines the extent to which childhood literacy rates are associated with parents’ and teachers’ perceptions of community violence and cohesion, following participation in a large-scale school feeding program in the Department of Intibucá, Honduras. Primary school children (n = 3,147) from 176 schools completed standardized literacy tests. Scores were linked to parents’ (n = 328) and teachers’ (n = 537) responses about community cohesion and violence. Social bonding among parents was positively associated with children’s literacy. Community violence reported by teachers exerted a negative influence. The authors discuss these results in light of how vertically focused interventions such as school feeding can be integrated to account for the specific contextual factors that affect, and are affected by, the program itself.