Association of different types of playing surfaces with bone mass in growing girls     

Esther Ubago-Guisado  Jorge García-Unanue  Jorge López-Fernández  Javier Sánchez-Sánchez  Leonor Gallardo 《Journal of sports sciences》2017,35(15):1484-1492

The aim of this cross-sectional study was to compare bone mass in young female athletes playing ball games on different types of playing surfaces. About 120 girls, 9–13 years of age (10.6 ± 1.5 years old Tanner I–III) were recruited and divided into prepubertal and pubertal groups. The sample represented 3 groups of athletes: soccer (N = 40), basketball (N = 40), and handball (N = 40); and 6 different playing surfaces (soccer – ground, soccer – artificial turf, basketball – synthetic, basketball – parquet, handball – synthetic, and handball – smooth concrete). Total and regional body composition (bone mass, fat mass, and lean mass) were measured by dual-energy X-ray absorptiometry (DXA). The mechanical properties of the surfaces (force reduction, vertical deformation, and energy return) were measured with the Advanced Artificial Athlete (Triple A) method. The degree of sexual development was determined using Tanner test. The pubertal group showed that soccer players on the ground, basketball players on synthetic, and handball players on smooth concrete had higher values of bone mineral content (BMC) and bone mineral density (BMD) (P < 0.05) than the soccer players on the artificial turf, basketball players on parquet, and handball players on synthetic. In conclusion, a hard playing surface, with less vertical deformation and force reduction, and greater energy return, is associated with higher levels of BMD and BMC in growing girls, regardless of the sport they practice.  相似文献   

Effects of plyometric jump training in female soccer player’s vertical jump height: A systematic review with meta-analysis     

Rodrigo Ramirez-Campillo  Javier Sanchez-Sanchez  Blanca Romero-Moraleda  Javier Yanci  Antonio García-Hermoso  Filipe Manuel Clemente 《Journal of sports sciences》2020,38(13):1475-1487

ABSTRACT

To assess the effects of plyometric jump training (PJT) in female soccer player’s vertical jump height, a review was conducted using the data sources PubMed, MEDLINE, Web Of Science and SCOPUS. Only peer-review articles were included. To qualify for inclusion in the meta-analysis, studies must have included (i) a PJT programme of at least 2 weeks, (ii) cohorts of healthy female soccer players with no restriction for age, (iii) a control group, (iv) a measure of countermovement jump (CMJ). The inverse variance random-effects model for meta-analyses was used. From 7,136 records initially identified through database searching, 8 were eligible for meta-analysis, comprising 9 training groups (n = 99) and 9 control groups (n = 94). The magnitude of the main effect was moderate (ES = 1.01 [95%CI = 0.36–1.66], Z = 3.04, p = 0.002). Sub-group analyses were performed (i.e., PJT frequency, duration and total number of sessions), revealing no significant subgroup differences (p = 0.34–0.96). Among the studies included in this review, none reported injury or other adverse effects. In conclusion, PJT is effective in female soccer players for the improvement of vertical jump height. In future, research must identify specific dose–response relationships following PJT, particularly in the long term.  相似文献   

Efficient query-by-example spoken document retrieval combining phone multigram representation and dynamic time warping     

Paula Lopez-Otero  Javier Parapar  Alvaro Barreiro 《Information processing & management》2019,56(1):43-60

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Individual and field citation distributions in 29 broad scientific fields     

Javier Ruiz-Castillo  Rodrigo Costas 《Journal of Informetrics》2018,12(3):868-892

Using an initial dataset consisting of 18.5 million distinct authors and 15 million distinct articles published in the period 2000–2016, which are classified into 29 broad scientific fields, we search for regularities at the individual level for very productive authors with citation distributions of a certain size, and for the existence of a macro-micro relationship between the skewness of a scientific field citation distribution and the characteristics of the individual citation distributions of the authors belonging to the field. Our main results are the following three. Firstly, although the skewness of individual citation distributions varies greatly within each field, their average skewness is of a similar order of magnitude in all fields. Secondly, as in the previous literature, field citation distributions are highly skewed and the degree of skewness is very similar across fields. Thirdly, the skewness of field citation distributions is essentially explained in terms of the average skewness of individual authors, as well as individuals’ differences in mean citation rates and the number of publications per author. These results have important conceptual and practical consequences: to understand the skewness of field citation distributions at any aggregate level we must simply explain the skewness of the individual citation distributions of their very productive authors.  相似文献   

Internal,External, and Government Political Efficacy: Effects on News Use,Discussion, and Political Participation     

Homero Gil de Zúñiga  Trevor Diehl  Alberto Ardévol-Abreu 《广播与电子媒介杂志》2017,61(3):574-596

News use and political discussion are often studied as important factors in understanding the effects of political efficacy on participation. However, measurements of external efficacy often blur distinctions between personal ability and government responsiveness. This study establishes a measure for perceptions of competence in the institutions of democratic government—government efficacy (GE). Drawing on panel survey data from the United States, confirmatory factor analysis introduces GE as a unique construct. Political efficacy dimensions are tested for their impact on news consumption, discussion, and political participation. Results add to the extant literature revolving the role of political efficacy on news use, discussion, and participation.  相似文献   

Maximizing and assessing a one-shot information literacy session: A case study     

Esther L. Gil 《Journal of Business & Finance Librarianship》2017,22(2):97-110

This case study describes collaboration between an instructor and business librarian to maximize a one-shot information literacy session for a required marketing class for business majors. It includes an active-learning exercise where groups use three key business databases to conduct a company and industry analysis and an environmental scan for a company. The instructor then guides them in developing a strengths, weaknesses, opportunities, threats (SWOT) analysis. This session prepares students for the SWOT analysis they will have to submit for their actual projects. This article includes assessment of groups' in-class exercises as well as citation analysis of the assignments they turned in for their actual projects.  相似文献   

Abuse of children in institutions     

Eliana Gil M.A.  Kathleen Baxter M.S.W. 《Child abuse & neglect》1979,3(3-4)

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Attacking and defensive styles of play in soccer: analysis of Spanish and English elite teams     

Javier Fernandez-Navarro  Luis Fradua  Asier Zubillaga  Paul R. Ford  Allistair P. McRobert 《Journal of sports sciences》2016,34(24):2195-2204

ABSTRACT

The aim of this study was to define and categorise different styles of play in elite soccer and associated performance indicators by using factor analysis. Furthermore, the observed teams were categorised using all factor scores. Data were collected from 97 matches from the Spanish La Liga and the English Premier League from the seasons 2006–2007 and 2010–2011 using the Amisco® system. A total of 19 performance indicators, 14 describing aspects of attacking play and five describing aspects of defensive play, were included in the factor analysis. Six factors, representing 12 different styles of play (eight attacking and four defensive), had eigenvalues greater than 1 and explained 87.54% of the total variance. Direct and possession styles of play, defined by factor 1, were the most apparent styles. Factor analysis used the performance indicators to cluster each team’s style of play. Findings showed that a team’s style of play was defined by specific performance indicators and, consequently, teams can be classified to create a playing style profile. For practical implications, playing styles profiling can be used to compare different teams and prepare for opponents in competition. Moreover, teams could use specific training drills directed to improve their styles of play.  相似文献   

Comparison of the force-, velocity-, and power-time curves recorded with a force plate and a linear velocity transducer     

Amador García-Ramos  Igor Stirn  Vojko Strojnik  Paulino Padial  Blanca De la Fuente  Javier Argüelles-Cienfuegos 《Sports biomechanics / International Society of Biomechanics in Sports》2016,15(3):329-341

This study aimed to correlate, compare, and determine the reliability of force, velocity, and power values collected with a force plate (FP) and a linear transducer during loaded jumps. Twenty-three swimmers performed an incremental loading test at 25, 50, 75, and 100% of their own body weight on a FP. A linear velocity transducer (LVT) was attached to the bar to assess the peak and the mean values of force, velocity, and power. Both the peak variables (r = 0.94 – 0.99 for peak force, r = 0.83 – 0.91 for peak velocity, and r = 0.90–0.94 for peak power; p < 0.001) and the mean variables (r = 0.96–0.99 for mean force, r = 0.87–0.89 for mean velocity, and r = 0.93–0.96 for mean power; p < 0.001) were strongly correlated between both measurement tools. Differences in the shape of the force-, velocity-, and power-time curves were observed. The LVT data showed a steeper increase in these variables at the beginning of the movement, while the FP recorded larger values in the latter part. Peak values were more reliable than mean values. These results suggest that the LVT is a valid tool for the assessment of loaded squat jump.  相似文献   

Effect of defence response time during lunge in foil fencing     

Carmen Gutiérrez-Cruz  F. Javier Rojas  Marcos Gutiérrez-Davila 《Journal of sports sciences》2016,34(7):651-657

The aim of this study was to analyse the effect of stimulus change timing on reaction response time parameters, horizontal velocity of the centre of mass (CM) and precision during offensive actions in fencing. Twelve fencers from the Spanish National Foil Team were included in the study. Two 500 Hz force plates were used to register the horizontal component of the reaction force while a 3D video camera set at 250 Hz recorded the spatial position of 11 body markers and a projector connected to a programmed stopwatch projected a moving target (stimulus) on a screen. When the circle (target) appeared in the centre of the plastron, fencers had to execute a step-forward-lunge as fast as possible, trying to touch the circle with the tip of the foil. During the lunge, the position of the target could randomly shift or not to three different positions. The stimulus change was performed randomly at four different times with a progressive delay. The results show that target changes did not have any effect when they occurred at the beginning of the movement sequence. However, when the target change was delayed, reaction and movement times increased and the technical execution of the lunge changed, leading to more errors.  相似文献