Key somatic variables associated with,and differences between the 4 swimming strokes     

Alan M. Nevill  Yassine Negra  Tony D. Myers  Senda Sammoud  Helmi Chaabene 《Journal of sports sciences》2020,38(7):787-794

ABSTRACT

This study identified key somatic and demographic characteristics that benefit all swimmers and, at the same time, identified further characteristics that benefit only specific swimming strokes. Three hundred sixty-three competitive-level swimmers (male [n = 202]; female [n = 161]) participated in the study. We adopted a multiplicative, allometric regression model to identify the key characteristics associated with 100 m swimming speeds (controlling for age). The model was refined using backward elimination. Characteristics that benefited some but not all strokes were identified by introducing stroke-by-predictor variable interactions. The regression analysis revealed 7 “common” characteristics that benefited all swimmers suggesting that all swimmers benefit from having less body fat, broad shoulders and hips, a greater arm span (but shorter lower arms) and greater forearm girths with smaller relaxed arm girths. The 4 stroke-specific characteristics reveal that backstroke swimmers benefit from longer backs, a finding that can be likened to boats with longer hulls also travel faster through the water. Other stroke-by-predictor variable interactions (taken together) identified that butterfly swimmers are characterized by greater muscularity in the lower legs. These results highlight the importance of considering somatic and demographic characteristics of young swimmers for talent identification purposes (i.e., to ensure that swimmers realize their most appropriate strokes).  相似文献   

The biomechanical characteristics of high-performance endurance running     

Stephen J. Preece  Christopher Bramah  Duncan Mason 《European Journal of Sport Science》2019,19(6):784-792

The biomechanical profile of high-level endurance runners may represent a useful model that could be used for developing training programmes designed to improve running style. This study, therefore, sought to compare the biomechanical characteristics of high-performance and recreational runners. Kinematic and kinetic measurements were taken during overground running from a cohort of 14 high-performance (8 male) and 14 recreational (8 male) runners, at four speeds ranging from 3.3 to 5.6?m?s^?1. Two-way ANOVA analysis was then used to explore group and speed effects and principal component analysis used to explore the interdependence of the tested variables. The data showed the high-performance runners to have a gait style characterised by an increased vertical velocity of the centre of mass and a flight time that was 11% longer than the recreational group. The high-performance group were also observed to adopt a forefoot strike pattern, to contact the ground with their foot closer to their body and to have a larger ankle moment. Importantly, although observed group differences were mostly independent of speed, the tested variables showed a high degree of interdependence suggesting an underlying unitary phenomenon. This is the first study to compare high-performance and recreational runners across a full range of kinematic and kinetic variables. The results suggest that high-performance runners maintain stride length with a prolonged aerial phase, rather than by landing with a more extended knee. These findings motivate future intervention studies that should investigate whether recreational runners could benefit from instruction to decrease shank inclination at foot contact.  相似文献   

基于单向流固耦合的不同风速下帆板帆翼空气动力性能仿真     

雷晓珊  马勇  蔺世杰 《武汉体育学院学报》2019,53(11):95-100

目的：探究不同风速对帆板帆翼结构以及周围流场的影响。方法：以奥运女子级别的Neil Pryde RS：X帆板帆翼为研究对象，考虑空气动力与结构的流固耦合效应，利用ANSYS Workbench进行单向流固耦合分析。结果：Realizable模型适合计算帆翼周围的流场湍流度，在风速为2m/s时帆翼升阻比最大；随着风速的增大，帆翼面发生变形和振动会导致风激振现象、背风面产生明显的涡脱现象，且帆翼表面应力区增大，全帆的应变逐步增加。结论：不同风速下的帆翼迎风面和背风面的压力分布、帆翼整体空气动力有一定差异，运动员比赛中应该根据当时风况调整帆翼参数。  相似文献   

Exploring mechanisms of rapid automatized naming to arithmetic skills in Chinese primary schoolers     

Yiji Wang  Xiaolin Ye  Ciping Deng 《Psychology in the schools》2020,57(4):556-571

Rapid automatized naming (RAN) is associated with children's arithmetic performance, which is multifactorial by nature and consists of arithmetic fluency, arithmetic procedure, and word problems. Yet, it is unclear whether RAN can predict all key aspects of arithmetic skills independently and what cognitive mechanisms may explain this relation. Using a sample of Chinese primary school students (N = 170), results showed that while RAN was associated with all key aspects of arithmetic skills, the relations of RAN–arithmetic procedure and RAN–word problems may be dependent on that of RAN–arithmetic fluency. Supporting the processing speed hypothesis, results further suggested that processing speed may underlie the relation between RAN and arithmetic performance. Findings made unique contribution to understanding the effect of RAN on arithmetic performance and cognitive mechanisms that may underpin this association in the context of Chinese culture.  相似文献   

Power training in elite young soccer players: Effects of using loads above or below the optimum power zone     

Irineu Loturco  Lucas A. Pereira  Valter P. Reis  Chris Bishop  Vinicius Zanetti  Pedro E. Alcaraz 《Journal of sports sciences》2020,38(11-12):1416-1422

ABSTRACT

This study aimed to examine the effects of two jump squat (JS) training programs involving different loading ranges in under-20 soccer players during a preseason period. Twenty-three elite young soccer players performed sprint speed (at 5-, 10-, and 20-m), change-of-direction (COD) speed, JS peak-power (PP), and countermovement jump (CMJ) tests pre and post four weeks of training. Athletes were pair-matched in two groups according to their optimum power loads (OPL) as follows: lower than OPL (LOPL; athletes who trained at a load 20% lower than the OPL) and higher than OPL (HOPL; athletes who trained at a load 20% higher than the OPL). Magnitude-based inferences were used to compare pre- and post-training measures. Meaningful increases in the PP JS were observed for both groups. Likely and possible improvements were observed in the 5- and 10-m sprint velocity in the LOPL group. Meanwhile, possible and likely improvements were observed in the CMJ, 5- and 10-m sprint velocity, and COD speed in the HOPL group. Overall, both training schemes induced positive changes in athletic performance. Soccer coaches and sport scientists can implement the JS OPL-based training schemes presented here, either separately or combined, to improve the physical performance of youth soccer players.  相似文献   

变频调速技术在袜机上的应用   总被引：1，自引：0，他引：1  

刘浏 《中国科技信息》2007,(5):85-85,87

本文主要介绍了变频器在袜机应用中系统的构成、控制要点和重要性。  相似文献   

The Beautiful and the Ugly: Reading Ability Modulates Word Spacing Effects in Chinese Children     

Yu-Cheng Lin  Pei-Ying Lin 《Journal of Experimental Education》2017,85(3):501-512

There are no salient word spaces in Mandarin Chinese. Thus, it is unclear whether word spacing information differentially affects the reading speed of children with and without reading difficulties (RD). In the present study, native Chinese-speaking children of differential reading abilities were tested with Chinese text in un-spaced versus spaced versions at different time points during training. The results indicated that spaced texts slow down reading speeds in children without RD. In contrast, spaced texts improved reading speeds in children with reading difficulties after some training took place. These findings suggest that the effect of word spacing information on Chinese reading might vary as a function of individual differences in reading abilities. We argue that children with RD can accommodate to the spaced text better than children without RD and that they can take advantage of using bottom-up spacing information to segment and recognize words in text.  相似文献   

基于时间竞争的速度营销     

金开好 《安徽师范大学学报(人文社会科学版)》2007,35(4):385-389

随着信息网络技术的发展,企业面临的经营环境发生了变化,速度越来越影响市场营销,冲击着传统营销组合方式。整合营销资源,构建信息网络平台．提高反应能力．创造速度优势。这是赢得市场竞争胜利的关键所在。  相似文献   

Letter names, letter sounds and phonological awareness: an examination of kindergarten children across letters and of letters across children     

Mary Ann Evans  Michelle Bell  Deborah Shaw  Shelley Moretti  Jodi Page 《Reading and writing》2006,19(9):959-989

In this study 149 kindergarten children were assessed for knowledge of letter names and letter sounds, phonological awareness, and cognitive abilities. Through this it examined child and letter characteristics influencing the acquisition of alphabetic knowledge in a naturalistic context, the relationship between letter-sound knowledge and letter-name knowledge, and the prediction of Grade 1 phonological awareness and word identification from these variables. Knowledge of letter sounds was better for vowels and for letters with consonant–vowel names than for those with vowel–consonant names or names bearing little relationship to their sounds. However, there were anomalies within each category reflecting characteristics of the individual letters. Structural equation modelling showed that cognitive ability, comprising receptive vocabulary, non-verbal reasoning, rapid automatized naming of colours, and phonological memory significantly contributed to alphabetic knowledge and phonological awareness. In turn, letter-name knowledge but not phonological awareness predicted letter-sound knowledge and subsequent reading skill.This research was supported by a grant from the Social Sciences and Humanities Research Council of Canada to the first author. Thank you is extended to the participating schools and children and to Ian Newby-Clark for his orientation to AMOS. Michelle Bell, Shelly Moretti and Jodi Page have since graduated from the University of Guelph  相似文献   

The relationship of rapid serial naming and word reading in normally developing readers: An exploratory model     

Cutting  Laurie E.  Denckla  Martha Bridge 《Reading and writing》2001,14(7-8):673-705

Even though researchers have established that rapid serial naming (RSN), or the ability to name within a restricted category of visual stimuli quickly, is a significant predictor of word reading, the predictive nature of RSN is not well understood. To investigate the relationship of RSN and other variables thought to contribute to beginning word reading (phonological awareness, orthographic knowledge, memory span, processing speed, and articulation), a preliminary/exploratory model of word reading was developed and then tested by path analysis. Results indicated that no variable in the model could fully `explain' RSN; processing speed, but not articulation, contributed to RSN performance. RSN and orthographic knowledge were significantly related, but this relationship was due to the effects of processing speed. In terms of their unique contributions to the variance in word reading, RSN, phonological awareness, and orthographic knowledge were independent of each other. While these results pertain only to normal readers and are preliminary in nature, they may provide a basis for a clear interpretation of similar studies conducted with both normal and dyslexic readers.  相似文献