Mechanical determinants of acceleration and maximal sprinting speed in highly trained young soccer players     

Martin Buchheit  Pierre Samozino  Jonathan Alexander Glynn  Ben Simpson Michael  Hani Al Haddad  Alberto Mendez-Villanueva 《Journal of sports sciences》2014,32(20):1906-1913

Abstract

The aim of the present study was to examine, in highly trained young soccer players, the mechanical horizontal determinants of acceleration (Acc) and maximal sprinting speed (MSS). Eighty-six players (14.1 ± 2.4 year) performed a 40-m sprint to assess Acc and MSS. Speed was measured with a 100-Hz radar, and theoretical maximal velocity (V₀), horizontal force (F₀) and horizontal power (P_max) were calculated. Within each age group, players were classified as high Acc/fast MSS (>2% faster than group mean), medium (between ?2% and +2%), and low/slow (>2% slower). Acc and MSS were very largely correlated (?0.79; 90% confidence limit [?0.85; ?0.71]). The determinants (multiple regression r² = 0.84 [0.78; 0.89]) of Acc were V₀ (partial r: 0.80 [0.72; 0.86]) and F₀ (0.57 [0.44; 0.68]); those of MSS (r² = 0.96 [0.94; 0.97]) were V₀ (0.96 [0.94; 0.97]) and P_max (0.73 [0.63; ?0.80]). High/Med have likely greater F₀ (Cohen’s d: +0.8 [0.0; 1.5]), V₀ (+0.6 [?0.1; 1.3]) and P_max (+0.9 [0.2; 1.7]) than Low/Med. High/Fast have an almost certainly faster V₀ (+2.1 [1.5; 2.7]) and a likely greater P_max (+0.6 [?0.1; 1.3]) than High/Med, with no clear differences in F₀ (?0.0 [?0.7; 0.6]). Speed may be a generic quality, but the mechanical horizontal determinants of Acc and MSS differ. While maximal speed training may improve both Acc and MSS, improving horizontal force production capability may be efficient to enhance sprinting performance over short distances.  相似文献   

一类含临界指标的双调和方程解的存在性     

赵春燕  胡云学 《环球赛鸽科技》2014,(32)

本文研究以下具有Navier边界,含临界指标的双调和方程解的存在性：其中Ω为RN中一个包含原点的具有光滑边界的有界区域,N≥5;10;2*=2NN-4为Sobolev临界指数。通过在Nehari流形上抽取PS序列,得到方程非平凡解的存在性。  相似文献   

Constraints on dynamic stability during forward,backward and lateral locomotion in skilled football players     

Sina Mehdizadeh  Keith Davids 《European Journal of Sport Science》2016,16(2):190-198

The aim of this study was to investigate effects of speed and plane of motion on stability during locomotion in skilled football players. Ten male national-level football players participated in this study to run forward, backward and in lateral directions on a treadmill at 80%, 100% and 120% of their preferred running speeds. The coordinate data of passive reflective markers attached to body segments were recorded using motion capture systems. Time series data obtained from the ankle marker were used for further analyses. The largest finite-time Lyapunov exponent and maximum Floquet multiplier were adopted to quantify local and orbital dynamic stabilities, respectively. Results showed that speed did not significantly change local and orbital dynamic stabilities in any of running patterns. However, both local and orbital dynamic stability were significantly higher in the secondary plane of progression. Data revealed that in running, unlike walking, stability in the direction perpendicular to the direction of running is significantly higher, implying that less active control is required in the secondary plane of progression. The results of this study could be useful in sports training and rehabilitation programmes where development of fundamental exercise programmes that challenge both speed and the ability to maintain stability might produce a tangible enhancement of athletic skill level.  相似文献   

一类线性微分方程解复振荡结果的综述     

于书敏 《通化师范学院学报》2002,23(2):7-11

本文讨论二阶方程f“ (R1(Z)e^P1(z) R2(Z)e^P2(z) Q(Z)f=0，（其中P1（Z）＝ζ1Z^n ……，P2（Z）＝ζ2Z^n为非常数多项式。R1（Z）≡0,R2(Z)≠0，Q（Z）为级小于n的整函数）在ζ1／ζ2的条件下，任一非平凡解的零收敛指数。  相似文献   

Complex oscillation of certain high non-homogeneous linear differential equations     

LI Chun-hong LI Jiang-tao 《重庆大学学报(英文版)》2005,4(4):233-238

1 Introduction and main results a Im this paper, we use the standard notations of the Nevanlinna theory (see Refs. [1-3]); and denote the order of growth of f ( z ) by σ ( f), the exponent of convergence of the zero-sequence and the sequence of distinct zeroes of f ( z ) by λ ( f) and λ ( f), respectively. It recalls the following definitions. Definition 1 [5]. Let f ( z )be a meromorphic function, then the hyper-order σ 2( f)of f ( z ) is defined by _____ 2 σ ( f ) = lr i→m∞ loglologg…  相似文献   

Hurst Exponent Analysis of Financial Time Series     

SANGHong－wei  MATian 《上海大学学报(英文版)》2001,5(4):269-272

Statistical properties of stock market time series and the implication of their Hurst exponents are discussed.Hurst exponets of HJIA (Dow Jones Industrial Average)components are tested using re-scaled range analysis.In addition to the original stock return series,the linear prediction errors of the daily returns are also tested.Numerical results show that the Hurst exponent analysis can provide some information about the statistical properties of the financial time series.  相似文献   

逻辑斯蒂映像混沌区的几个非线性特征量     

高思莉  肖青  齐欣  秦琴 《新乡师范高等专科学校学报》2003,17(2):10-14

运用非线性动力学的方法分析了逻辑斯蒂(Logiotic)映像混沌区的几个非线性特征量。采用重现图形(Recurrence plot analysis,RPA)和重现定量(Recurrence quantification analysis,RQA)分析法得出系统存在确定性的规律;计算了序列的关联维数、最大Lyapunov指数和近似熵(Approximate entropy,ApEn)。结果表明:关联维数介于1～2之间,系统的最大Lyapunov指数大于0,ApEn的值为0.676 460。  相似文献   

Chaotic phenomenon and the maximum predictable time scale of observation series of urban hourly water consumption     

柳景青  张土乔  俞申凯 《浙江大学学报(A卷英文版)》2004,5(9):1053-1059

The chaotic characteristics and maximum predictable time scale of the observation series of hourly water consumption in Hangzhou were investigated using the advanced algorithm presented here is based on the conventional Wolf's algorithm for the largest Lyapunov exponent. For comparison, the largest Lyapunov exponents of water consumption series with one-hour and 24-hour intervals were calculated respectively. The results indicated that chaotic characteristics obviously exist in the hourly water consumption system; and that observation series with 24-hour interval have longer maximum predictable scale than hourly series. These findings could have significant practical application for better prediction of urban hourly water consumption.  相似文献   

Short-Term Forecasting of Urban Water Consumption Based on the Largest Lyapunov Exponent     

赵鹏  张宏伟 《天津大学学报(英文版)》2007,13(3):191-194

Effective and exact short-termforecastingof urban wa-ter consumptionis veryimportant to on-line simulation andoptimal schedulingin municipal water supply management .Almost all traditional short-termpredictions use time seriesmethods,such as multi linear …  相似文献   

猕猴桃矿质元素DRIS标准研究     

周博  陈竹君  郝乾坤  王青宁  刘延超 《杨凌职业技术学院学报》2002,(2)

本实验采集了34个猕猴桃园叶样,并根据产量将亩产≥1000kg的17个园子划为高产组,亩产<1000kg的17个园划分低产组。对叶片中N、P、K、Mn、Cu、Zn6种元素含量进行测定和统计分析。结果表明:低产组大量元素需肥强度最大的主要为N,占该组的52.94%,微量元素需肥强度最大的以Zn和Cu为多,分别占该组的47.06%、41.18%;制定出猕猴桃园N、P、K、Mn、Cu、Zn的DRIS指数分级标准,其适宜指数范围分别为-4.003～5.202,4.002～4.922,4.993～6.465,9.733～7.675,1.621～1.332,5.317～3.998;各园的需肥顺序用图示法和用指数法判断,其结果一致。  相似文献