Quasi-static mechanical behaviour of soils used for natural turf sports surfaces and stud force prediction

The quasi-static testing of soils used in natural turf pitches yields key parameters in soil modelling, including elastic moduli, Poisson’s ratio and Mohr–Coulomb parameters for shearing resistance and cohesion in soil. The bulk strength of a Sand soil used in the construction of elite sports surfaces was found to increase initially and then decrease with increasing water content due to apparent cohesion effects. For a Clay Loam soil, more common in recreational facilities, shear strength decreased with water content. Reducing density resulted in a reduction of shear strength and elastic moduli in both soils due to reduced packing of particles reducing particle–particle contact surface area. The effect of roots on the shear strength of a Sand soil was not significant but reduced elastic moduli significantly. Horizontal forces measured during running and turning in a biomechanics laboratory were in good agreement with forces predicted using a simple quasi-static soil model for coarse-grained (Sand) soils although this was not the case with the Clay Loam soil.     

Mechanical behaviour of natural turf sports pitches across a season

A study assessing the mechanical behaviour of six natural turf pitches of varying sporting level and surface construction was undertaken over a period of 10?months, spanning a sporting season (August 2010 to May 2011). Penetration resistance and shear resistance were measured with the GoingStick^?, impact hardness and surface energy absorption were measured with the 2.25?kg Clegg Impact Soil Tester and the Dynamic Surface Tester device, respectively. The two sand rootzone pitches were more resistant to deformation and less variable in their impact behaviour (impact hardness and energy absorption) through the season than the native soil pitches containing greater proportions of silt and clay. Greater consistency was shown for penetration resistance and shear resistance on one of the sand rootzone pitches, with the other behaving similar to the native soil pitches for these parameters. The sand rootzone surfaces exhibited greater (P?<?0.05) impact hardness than the native soil pitches in the winter period of the season (November to mid-March) compared to the beginning or end periods of the season, where data were statistically similar (P?>?0.05). The greater consistency of sand rootzone surfaces should be considered for the effect it may have on player and team performance, and injury potential. Analysis of data against Performance Quality Standard benchmarks indicated that all data on the sand rootzones exceeded preferred values for impact hardness, indicating these ranges may be obsolete for the modern elite natural turf surface.     

Skin friction related behaviour of artificial turf systems

The occurrence of skin friction related injuries is an issue for artificial turf sports pitches and remains a barrier to their acceptance. The purpose of this study was to evaluate the current industry standard Securisport® Sports Surface Tester that measures skin surface related frictional behaviour of artificial turf. Little research has been published about the device and its efficacy, despite its widespread use as a standard FIFA test instrument. To achieve a range of frictional behaviours, several “third generation” (3G) carpet and infill combinations were investigated; friction time profiles throughout the Securisport rotations were assessed in combination with independent measurements of skin roughness before and after friction testing via 3D surface scanning. The results indicated that carpets without infill had greatest friction (coefficients of friction 0.97–1.20) while those completely filled with sand or rubber had similar and lower values independent of carpet type (coefficient of friction (COF) ≈0.57). Surface roughness of a silicone skin (s-skin) decreased after friction testing, with the largest change on sand infilled surfaces, indicating an “abrasive” polishing effect. The combined data show that the s-skin is damaged in a surface-specific manner, thus the Securisport COF values appear to be a poor measure of the potential for skin abrasion. It is proposed that the change in s-skin roughness improves assessment of the potential for skin damage when players slide on artificial turf.     

Hardness measurement of natural and hybrid turf soccer fields

Understanding the surface hardness of soccer fields is essential to evaluate the risk of injury and also its influence on the playing behavior of soccer players. In this context, newly developed hybrid turf systems have to be tested for their surface hardness with regard to the increased risk of injury on hard sports surfaces. The hardness of a soccer field can be quantitatively measured using an apparatus with a cylindrical weight that is dropped from a defined height. Since this procedure was first used for road construction, there are few studies investigating its use on sports grounds. This has led to inconsistencies in methodology and the absence of evaluation guidelines for classifying the hardness of soccer fields. This paper considers how turf systems (natural turf and hybrid turf) differ in their hardness and how this method can be used for different soccer turf systems. Natural turf systems, stitched turf systems, hybrid turf-bearing layer systems and woven mat systems were investigated. The assessment results from a comparative representation of hardness values of different soccer fields. By comparison, natural turf systems were found to be the softest, while woven mat systems were the hardest. Furthermore, the parameters that might affect the hardness were investigated. The influence of the measured soil parameters decreases with an increasing number of measurements per measuring point. Turf system-specific correlations make it possible to reduce the amount of measurement effort.     

Spatial characterisation of natural and third-generation artificial turf football pitches

In contrast to the situation with early artificial turf pitches, little information has previously been published on the characterisation of third-generation artificial surfaces. The spatial variation of ball rebound resilience and rotational resistance were measured here under dry conditions, late in the season, for two natural turf football pitches and a recently laid third-generation artificial turf pitch. Data for the natural turf pitches show a wider variation with position on the pitch than for the artificial pitch. The latter surface showed remarkable consistency in both quantities measured. Surprisingly, all ball rebound resilience data and some of the rotational resistance values were found to lie outside current FIFA specifications, possibly due to the level of wear in natural turf at this stage of the season. For the artificial turf, the deterioration in properties over a period of 6 months is significant and suggests more frequent testing is needed. Taking data from various pitch positions, the two measured quantities were shown for the first time, as far as we are aware, to be inversely related for both natural turf pitches. This correlation may be largely attributed to differences in the extent of grass cover and/or soil compaction. For artificial turf, the lack of variation in measured quantities with pitch position precluded the determination of any correlation.     

我国竞技体育发展的动力机制研究

我国竞技体育在2008年北京奥运会上取得了新突破,成绩的获得主要得益于竞技体育良好的动力机制。我国竞技体育的发展主要依靠保障机制、服务机制和支持机制。其中举国体制和奥运战略为竞技体育提供制度保障;和平崛起、综合国力和和谐社会为竞技体育提供外界服务;经济、文化和教育为竞技体育提供重要支持。     

天然抗氧化剂在体育运动中的运用及展望

在众多引起运动性疲劳及运动损伤的原因中,自由基对机体的影响日益受到国内外科研人员的广泛关注。本文就竞技体育运动过程中自由基的产生及对机体的影响、天然抗氧化剂的作用优势及发展前景等方面作以归纳,强调在运动领域应注意抗氧化剂尤其是天然抗氧化剂的合理应用。     

Accuracy of an UWB-based position tracking system used for time-motion analyses in game sports

Abstract

The main aim of this study was to determine the accuracy of the ultra-wideband (UWB)-based positioning system Ubisense, which is used for time-motion analysis in sports. Furthermore, some alternatives for positioning the system's transponders on the atheletes, as well as the accuracy depending on the location of measurement, were tested. Therefore, in a pre-study, some basic issues were examined (measurement assumptions and consistency and location of the system's transponder used for position detection), and position measurements at the borders and in the centre of a basketball field were performed. In the main study, 13 male basketball players (15.8 years ± 0.6; 187.9 height ± 3.4; 77.5 weight ± 3.7), equipped with a Ubisense transponder mounted on top of their heads, handled a trundle wheel during simulated match play. The players with the trundle wheel participated passively in the match by following one of the ten competing players. The distance measurements of the trundle wheel were used as reference values and compared to the Ubisense distance estimations. Best results were found with the measurements of a single mounted transponder on top of the athlete's heads. No differences were detectable in the accuracy between measurements in the centre and at the borders of the basketball field. The (Ubisense) system's difference to the (trundle wheel) reference was 3.45 ± 1.99%, resulting in 95% limits of agreement of ?0.46–7.35%. The study indicates the examined system's sufficient accuracy for time-motion analysis in basketball.     

新疆少数民族传统体育项目场地发展的特殊性及契机

根据对新疆少数民族传统体育项目场地现状的调查，认为“有用论”和“无用论”之争、区域发展的个性化、衡量标准的难统一、一场多用的普遍性、需求与供给的城乡不平衡性是新疆少数民族传统体育项目场地发展的特殊性表现。新疆少数民族传统体育项目场地的发展应该把握“环天山万里体育长廊工程”全面实施的良好机遇，鼓励区域发展的个性化，加大现有场地的开发和运用的力度，转变观念将发展的重点从城市转向农村。     

Viscoelastic impact characterisation of solid sports balls used in the Irish sport of Hurling

In recent years, variability in behaviour of the sliotar, a small leather-bound ball used in the Irish sport of hurling, has become evident in championship matches. The inconsistency in performance was attributed to the range of constructions and material compositions of currently approved ball types. With a view to adopting a standard core, a new methodology has been commissioned to assess the dynamic impact behaviour of approved sliotar cores. In this paper, the relationship between the dynamic stiffness and the coefficient of restitution is presented with regard to material properties, ball construction and viscoelastic strain and strain-rate dependencies. The modern polymer ball types were shown to exhibit strain-rate sensitivity, while the performance of the traditional multi-compositional ball types exhibited lesser strain-rate dependence. The traditional balls types were shown to be up to 2.5 times stiffer than the modern ball types, with this finding having implications for ball energy dissipation.     

体育强国目标下发展群众体育的路径探讨

运用文献资料、调研等方法,在诠释富民、民生、强国等概念的基础上,解读体育强国和群众体育的内涵,阐述群众体育与体育强国之间的关系,探讨体育强国目标下发展群众体育的路径选择.分析认为,科学发展观是发展群众体育的指导思想,共享体育发展成果是发展群众体育的目标,强化政府服务职能是发展群众体育的前提,解决公平与效率问题是发展群众体育的关键,加强体育制度创新是发展群众体育的保障.     

“三民体育”在全民健身中的回归与发展

通过文献资料研究,辨析了"三民体育"的文化内涵,认为"三民体育"是中华体育文化的重要内容,更是开展全民健身的重要途径;随着我国经济社会的发展和文化活动的繁荣,"三民体育"已在全民健身活动中崭露头角,时代呼唤着"三民体育"的回归。建议挖掘和推广"三民体育"项目,积极应用于社会文化、健身、娱乐、休闲等活动中;建立"三民体育"文化实体;利用传统节日、民俗习惯和地域文化开展"三民体育"活动;促进"三民体育"进入校园,传承中华体育文化。     

Chemical degradation of a paraffin wax-based binder used in granular composite sport surfaces

Chemical changes in high-oil wax-based binders used in Thoroughbred horse racing synthetic surfaces are studied over a 7-year period in an effort to understand the effect of changes in the binder on track behavior. A wax or polymer binder is used to hold the sand, fiber, and rubber constituents together in addition to creating a hydrophobic coating on the sand. The binder was extracted from bulk samples obtained from sampling of a racetrack surface at the same location on a single racetrack. During the 7 years, the material components of the track were not altered nor was material added, although normal maintenance including daily harrowing and annual tilling was performed. The binder was separated via solvent extraction from the samples. Differences in chemical composition were determined through oil extraction, Fourier transform infrared spectroscopy (FTIR), gas chromatography (GC-FID), and differential scanning calorimetry (DSC). Results show chemical changes in the binder resulting from oxidation of the oil in the wax, as well as changes in wax molecular structure. The goal of this work is to better understand how the binder changes over time to help guide maintenance and replacement decisions. Other potential changes to the surface materials can include the addition of oil stabilizers and binder replenishment. If the time interval between surface replacements can be extended, it would enable racetracks to provide a consistent and potentially safer racing surface at a lower cost.     

Interaction of sedentary behaviour,sports participation and fitness with weight status in elementary school children

Abstract

Even though the effect of single components contributing to weight gain in children have been addressed only limited research is available on the combined association of sports participation, physical fitness and time spent watching TV with body weight in children. Baseline data from 1594 children (809 male; 785 female), 7.1±0.6 years of age participating in a large school-based intervention in southern Germany was used. Height and weight was measured and body mass index (BMI) percentiles (BMIPCT) were determined accordingly. Sports participation and time spent watching TV was assessed via parent questionnaire while fitness was determined via a composite fitness test. Combined and single associations of sports participation, TV time and fitness with BMIPCT and weight status were assessed via ANCOVA as well as logistic regression analysis, controlling for age and sex. A significant interaction of TV time, sports participation and fitness on BMIPCT occurred, despite low correlations among the three components. Further, there was a combined association of sports participation and TV time on BMIPCT. TV time and fitness were also independently associated with BMIPCT. Similarly, only increased TV time and lower fitness were associated with a higher odds ratio for overweight/obesity. These results underline the complex interaction of TV time, sports participation and fitness with BMIPCT. In children, TV time and fitness have a stronger influence on BMIPCT compared to sports participation. Sports participation, however, may not reflect overall activity levels of children appropriately. More research is necessary to examine the complex interaction of various behaviours and fitness with BMIPCT.     

冰上教学与训练中交流技巧的研究

交流是教练员重要的基本技能.教练员在教学训练过程中所做的每一件事情都要通过交流去完成的.通过调查分析,对不同交流方式及其有效性进行了研究,目的在于为教练员提高交流技巧提供依据.     

The predicted risk of head injury from fall-related impacts on to third-generation artificial turf and grass soccer surfaces: A comparative biomechanical analysis

The risk of soccer players sustaining mild traumatic brain injury (MTBI) following head impact with a playing surface is unclear. This study investigates MTBI by performing headform impact tests from varying heights onto a range of third-generation artificial turf surfaces. Each turf was prepared as per manufacturers specifications within a laboratory, before being tested immediately following installation and then again after a bedding-in period. Each turf was tested dry and when wetted to saturation. Data from the laboratory tests were compared to an in situ third-generation surface and a professional grass surface. The surface performance threshold was set at a head impact criterion (HIC) = 400, which equates to a 10% risk of the head impact causing MTBI. All six third-generation surfaces had a >10% risk of MTBI from a fall >0.77 m; the inferior surfaces required a fall from just 0.46 m to have a 10% MTBI risk. Wetting the artificial turf did not produce a statistically significant improvement (P > 0.01). The in situ third-generation playing surface produced HIC values within the range of bedded-in experimental values. However, the natural turf pitch was the superior performer – necessitating fall heights exceeding those achievable during games to achieve HIC = 400.     

An examination of the Clegg impact hammer test with regard to the playing performance of synthetic sports surfaces

One of the tests used to evaluate the performance of sports surfaces measures the peak deceleration of a rigid mass during contact with the surface, after being dropped from a set height. It is widely used and is included in a number of international standards. The test was carried out using two drop heights on four different designs of artificial cricket pitch, with a full set of acceleration data being collected over the duration of impact. These data were then integrated twice with respect to time to produce velocity and displacement information. Oblique impacts of cricket balls were also carried out and analysed using a high-speed video system to evaluate the playing performance of each pitch design. It was found that, although the pitches gave quite different readings of peak deceleration, they produced similar values for coefficient of restitution and were therefore considered to ‘play’ in a very similar way. This was due to a high peak deceleration reading being accompanied by a short contact time and low peak deceleration being accompanied by a long contact time, meaning that the change in momentum was similar in both cases. It was concluded that for accelerometer tests to be useful, all the acceleration-time data should be analysed, rather than the peak value alone.     

向体育强国迈进的体育产业资本市场创新体系构建研究

采用资料调研、专家调查和可拓分析等方法,分析了体育产业的资本化发展是向体育强国迈进的体育产业资本市场创新体系构建的基础,论述了向体育强国迈进的体育产业资本市场创新体系构建的重要价值,提出了实现向体育强国迈进的体育产业资本市场创新体系的构建路径:构建向体育强国迈进的体育产业资本市场创新体系的投融资组织优化结构及运作渠道;加快实现向体育强国迈进的体育产业资本市场创新体系构建的法制化建设;借成功举办奥运会、亚运会和世博会机遇推动体育企业和职业体育俱乐部上市融资.