Dynamic behaviour of soils used for natural turf sports surfaces

The modulus and damping properties of soils in compression are a function of soil type, water content, stress history and loading rate. To model human–surface interaction with natural turf sports surfaces, stiffness and damping properties must be determined at dynamic loading rates. Two contrasting soil types, a Sand and a Clay Loam, commonly used in sports surfaces were loaded uniaxially to 2 kN at loading rates between 0.6 and 6 kN s⁻¹ in modified dynamic soil testing apparatus. Soils were compacted prior to loading but initial cycles resulted in viscoplastic deformation, with strain accumulation with repeated cycles of loading. Ultimately a resilient, viscoelastic steady-state equilibrium with loading was established. Resilient modulus and damping ratio varied with soil type, water content, stress history and increased significantly with loading rate. The resilient modulus of the Sand soil, typical of modern free-draining sand construction natural turf sports surfaces, was significantly greater than that of a Clay Loam soil more characteristic of traditional natural turf surfaces; reducing water content caused an increase in modulus and a decrease in damping ratio in the Clay Loam soil. Determination of these properties provides initial data for the modelling natural turf surface behaviour in terms of both ball and human interactions, with further research required to determine the effect of both grass roots and leaves on mechanical behaviour.     

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.     

Ground reaction force measures when running in soccer boots and soccer training shoes on a natural turf surface

There are differences in ground reaction force when wearing soccer boots compared with training shoes on a natural turf surface. Two natural-turf-covered force platforms, located outdoors in a field, allowed comparison of performance when six-studded soccer boots and soccer training shoes were worn during straight fast running (5.4 m s^-1 ± 0.27 m s-1) and slow running (4.4 m^s-1 ± 0.22 m s^-1). Six male soccer players (mean age: 25 ± 4.18 years; mean mass 79.7 ±9.32 kg) struck the first platform with the right foot and the second platform with the left foot. In fast running, the mean vertical impact peak was significantly greater in soccer boots (2.706 BW) than in training shoes (2.496 BW) when both the right and left foot were considered together and averaged (P = 0.003). Similarly, the mean vertical impact peak loading rate was greater when wearing soccer boots at 26.09 BWs^-1 compared to training shoes (21.32 BWs^-1;P = 0.002). Notably, the mean vertical impact peak loading rate of the left foot (boots: 28.07 BWs^-1; shoes: 22.52 BWs^-1) was significantly greater than the right foot (boots: 24.11 BWs^-1; shoes: 20.11 BWs^-1) in both boots and shoes (P = 0.018). The braking force was greater for the left foot (P = 0.013). In contrast, mean peak vertical propulsion forces were greater for the right foot (P > 0.001) when either soccer boots or training shoes were considered. Similar significant trends were evident in slow running, and, notably, in both soccer boots and training shoes medial forces were greater for the left foot (P = 0.008) and lateral forces greater for the right foot (P = 0.011). This study showed the natural turf ground reaction force measurement system can highlight differences in footwear in an ecological environment. Greater forces and impact loading rates occurred during running activity in soccer boots than in training shoes, with soccer boots showing reduced shock attenuation at impact. Such findings may have implications for impact-related injuries with sustained exposure, especially on harder natural-turf surfaces. There were differences in the forces occurring at the right and left feet with the ground, thus suggesting the use of bipedal monitoring of ground reaction forces.     

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.     

Effects of two football stud configurations on biomechanical characteristics of single-leg landing and cutting movements on infilled synthetic turf

Multiple playing surfaces and footwear used in American football warrant a better understanding of relationship between different combinations of turf and footwear. The purpose of this study was to examine effects of shoe and stud types on ground reaction force (GRF) and ankle and knee kinematics of a 180° cut and a single-leg 90° land-cut on synthetic turf. Fourteen recreational football players performed five trials of the 180° cut and 90° land-cut in three shoe conditions: non-studded running shoe, and football shoe with natural and synthetic turf studs. Variables were analyzed with a 3 × 2 (shoe × movement) repeated measures analysis of variance (p < 0.05). Peak vertical GRF (p < 0.001) and loading rate (p < 0.001) were greater during 90° land-cut than 180° cut. For 180° cut, natural turf studs produced smaller peak medial GRFs compared to synthetic turf studs and non-studded shoe (p = 0.012). For land-cut, peak eversion velocity was reduced in running shoes compared to natural (p = 0.016) and synthetic (p = 0.002) turf studs. The 90° land-cut movement resulted in greater peak vertical GRF and loading rate compared to the 180° cut. Overall, increased GRFs in the 90° land-cut movement may increase the chance of injury.     

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。     

农民体育健身行为实现的内化力挖掘研究

建国以来,中国农村居民的体育思想不断改变,尤其是近几年来实现了体育健身思想的突破式跃进,但健身思想的建立并不等于健身行为的实现.调查显示,徐州市农民体育健身思想与健身行为之间Pearson相关性系数仅为0.268.针对农民体育健身思想与健身行为矛盾的现状,运用文献资料、问卷调查等研究方法,以凯尔曼态度转化理论为基础,指出两者之间的矛盾根源在于农民体育健身态度内化力的缺失.据此,对农民体育健身行为内化力的挖掘进行了研究,并从"不同组织机构环境氛围作用、多方群体榜样带动作用、传媒宣传劝服作用、影视熏陶感染作用"四个方面对健身内化力形成的路径挖掘进行了探讨,旨在为农民体育健身态度内化过程的实现奠定理论基础,进而加速其由健身思想向健身行为的跨越.     

对我国竞技体育后备人才培养主体的比较研究

通过对我国高等体育院校附属竞技体校、体育运动学校和高校高水平运动队在2001-2004年周期中竞技体育人才培养上的横向比较,总结竞技体校人才培养的优势,指出竞技体校的人才培养模式符合我国未来竞技体育人才培养的发展趋势.     

机械类专业体育课程体系改革的探讨

提出机械类专业的人才培养模式和体育课程体系改革的主要指导思想——以学生为对象，以健康为主线，以科学的生活方式为目标，以余暇(课外)体育活动为主要形式；选择教材注重人体生物改造功能和文化、教育等功能；教学与指导、教法与学法协调发展。     

竞争与协同:专业运动训练系统可持续发展的核心动力

复杂的专业运动训练系统体现出自组织演进的特色,无论是教练员还是运动员,都无法独自成为这一系统演进的主导力量.运用协同学思想,积极探索并构建了专业运动训练系统可持续发展的新模式--协同模式.指出专业运动训练系统有序形成和可持续发展的前提条件是系统的开放与营造非平衡态,内在核心动力是构建非线性的竞争与协同机制,关键是序参量的形成与支配作用.协同学思想为运动训练系统和运动员运动技能的可持续发展,提供了一把理论"金钥匙"和一种有益的思考方式.     

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。     

“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。     

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.     

关于竞技体育职业化发展与部队体工队院校化管理的研究

根据我国竞技体育职业化发展的大趋势，提出了部队体工队实行院校化管理的理论构想和基本模式，以及需要解决的主要问题。     

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.