Timescales for exploratory tactical behaviour in football small-sided games     

Angel Ric  Robert Hristovski  Bruno Gonçalves  Lorena Torres  Jaime Sampaio  Carlota Torrents 《Journal of sports sciences》2016,34(18):1723-1730

The aim of this study was to identify the dynamics of tactical behaviour emerging on different timescales in football small-sided games and to quantify short- and long-term exploratory behaviour according to the number of opponents. Two teams of four professional male footballers played small-sided games against two different teams with a variable number of opponents (3, 5 and 7). Data were collected using a combination of systematic observation and a non-differential global positioning system (15 Hz). The temporal diversity and structural flexibility of the players were determined by calculating the dynamic overlap order parameter q, entropy and trapping strength. Analysis of the exploratory dynamics revealed two different timescales, forming a different metastable landscape of action for each constraint. Fast dynamics lasted on average a few seconds and consisted of changes in tactical patterns. The long timescale corresponded to the shared tasks of offence and defence lasting tens of seconds. The players’ tactical diversity decreased with an increasing number of opponents, especially in defence. Manipulating numerical imbalance is likely to promote changes in the diversity, unpredictability and flexibility of tactical solutions. The fact that the temporally nested structure of constraints shaped the emergence of tactical behaviour provides a new rationale for practice task design. The manipulation of numerical imbalance on the timescale of a few tens of seconds, on which the exploratory behaviour of players saturates, may help coaches to optimise the exploratory efficiency of the small-sided games.  相似文献   

Incremental training intensities increases loads on the lower back of elite female rowers     

Erica M. Buckeridge  Anthony M.J. Bull  Alison H. McGregor 《Journal of sports sciences》2016,34(4):369-378

Lumbar-pelvic kinematics change in response to increasing rowing stroke rates, but little is known about the effect of incremental stroke rates on changes in joint kinetics and their implications for injury. The purpose of this study was to quantify the effects of incremental rowing intensities on lower limb and lumbar-pelvic kinetics. Twelve female rowers performed an incremental test on a rowing ergometer. Kinematic data of rowers’ ankle, knee, hip and lumbar-pelvic joints, as well as external forces at the handle, seat and foot-stretchers of the rowing machine were recorded. Inter-segmental moments and forces were calculated using inverse dynamics and were compared across stroke rates using repeated measures ANOVA. Rowers exhibited increases in peak ankle and L5/S1 extensor moments, reductions in peak knee moments and no change in peak hip moments, with respect to stroke rate. Large shear and compressive forces were seen at L5/S1 and increased with stroke rate (P < 0.05). This coincided with increased levels of lumbar-pelvic flexion. High levels of lumbar-pelvic loading at higher stroke rates have implications with respect to injury and indicated that technique was declining, leading to increased lumbar-pelvic flexion. Such changes are not advantageous to performance and can potentially increase the risk of developing injuries.  相似文献   

Organismic integration as a dynamic process: a systematic review of empirical studies on change in behavioral regulations in exercise in adults     

Anna Wasserkampf  Jens Kleinert 《International review of sport and exercise psychology》2016,9(1):65-95

In facilitating the adoption of exercise behavior, attention should be directed towards the dynamic nature of behavioral regulations. Organismic integration theory presents a suitable framework for investigating fluctuations in behavioral regulations. However, current results pertaining to this issue revealed mixed findings. The aim of this review is to examine the empirical literature on the dynamic nature of organismic integration theory in exercise settings over time in adults. A systematic review of English articles using PsycINFO, PsycARTICLES, ScienceDirect, and SPORTDiscus was conducted including keywords of organismic integration theory, longitudinal designs, change in behavioral regulations, and exercise. Findings are summarized through quantitative analysis of the evidence. Regarding autonomous regulations, steady increases in regulations are observable that originate within the first weeks and persist for up to one year. Most studies reported no changes in controlled regulations, although in a few cases changes were observed six weeks after baseline or later. The review adds to the theoretical understanding of how behavioral regulations are internalized. However, whether changes in regulation occur depends on both the type of regulation and on contextual characteristics. Future research of longitudinal design is warranted to identify optimal periods in which individuals seek for increased support during exercise adoption.  相似文献   

非晶团簇Au19的熔化特征研究     

任世伟  刘振永  王爱坤  白占果  成立芬  孙敬伟 《石家庄学院学报》2006,8(6):14-19

介绍了分子动力学的基本原理和计算过程,模拟了Au19团簇从类固相到类液相的相变过程.将所得的数据绘制成图线,并进行了分析与讨论,结果发现Au19这种不规则的非晶团簇的熔化过程是分步完成的:首先是外层某些不稳定原子开始熔化,其次是其他外层原子也随能量的升高熔化,最后是随能量的不断升高,中心原子也完成了熔化过程,整个体系完成从类固相到类液相的相变过程.由此可以看出,Au19的熔化过程是分步完成的,有别于晶体团簇和其他结构规则的非晶团簇,是一个比较特殊的过程.  相似文献   

转变教育思想:知识经济的呼唤     

肖鹏 《毕节学院学报》2001,19(4):8-10

本文拟从知识经济这一视角,审视我国高等教育,指出必须转变过于大一统的教育思想,以学生主体性和个性的培养为教育的出发点和落脚点,才能培养与知识经济时代具有本质联系的创新型人才,改变培养的人才脱离和滞后经济建设的社会发展需要的现象。  相似文献   

Transient Responses of Flexible Non—uniform Spinning Shaft with Nonlinear and Asymmetric Supports     

ZHUHuai－liang 《上海大学学报(英文版)》2001,5(1):35-39

In this paper ,a hybrid approach was developed to investigate the transient responses of a multi-span non-uniform flexble spinning shaft with nonlinear and asymmetric supports.The non-uniform spinning shaft with variable parmeters was modeled as a Bernoulli-Euler beam column with sectional constant cross-section properties by the finite element method.The supporting stiffness behavior of the nonlinear supports was described as a piecewise-linear and asymmetric model.The equations of motion in the matrix form of a multi-span non-uniform spinning shaft with nonlinear and asymmetric supports were formulated using Hamilton‘s principle and the assumed mode method.As an example,a spinning rocket with many variable stiffness supports was numerically simulated by the direct integration method.The transient response and dynamic behavior of this rotate-dynamic system are analyzed.  相似文献   

金属铝置换硝酸中氢的实验设计     

李大塘  唐建生 《株洲师范高等专科学校学报》2007,12(2):13-15,22

成功地设计了金属铝置换硝酸中氢的实验装置与方法，旨在探索金属铝与硝酸的化学性质以及深刘理解硝酸浓度影响其产物的规律．研究发现，室温下用去膜并经氯化汞溶液处理过的铝箔与一定浓度的稀硝酸作用可产生氢气，而未经氯化汞溶液处理的铝箔与稀硝酸作用几乎检测不到氢气的生成．进一步研究显示硝酸的最高浓度为1．6mol／L，产生氢气最快时硝酸浓度为0．07mol／L．  相似文献   

过二硫酸铵与硫代硫酸钠反应的热力学和动力学     

李羚 《保山师专学报》2003,22(2):14-15

从热力学和动力学两方面，讨论了S2O8^2--S2O3^2-I^-系统中，S2O8^2-不与S2O3^2-直接发生反应的原因。  相似文献   

离子极化与键型关系的研究     

吕自学  王亚军等 《河西学院学报》2002,18(5):32-35

离子极化学键型有着重要的影响，结合卤素进行了探讨．  相似文献   

区域性传统音乐文化资源在地方高校音乐专业学科建设中的优势与价值     

李素娥 《襄樊学院学报》2011,32(9):70-73

文章从地方高校音乐专业办学与学科建设的现状入手,客观地分析了区域性传统音乐文化资源给地方高校音乐专业学科建设所带来的"天时、地利、人和"的优势,并以作者所在区域高校探索与实践的初步成效为举证,提出了开发和利用区域性传统音乐文化资源,并在当代新的背景下充分彰显其特色,使之成为学校专业建设、学科建设以至办学特色的重要元素,是当下地方高校音乐专业加强内涵建设、打造特色品牌、形成核心竞争力的重要途径。  相似文献