Effectiveness during ball screens in elite basketball games     

Miguel-Ángel Gómez  Otavio Battaglia  Alberto Lorenzo  Jorge Lorenzo  Sergio Jiménez  Jaime Sampaio 《Journal of sports sciences》2015,33(17):1844-1852

Ball screens are one of the most frequently used tactical behaviour in elite basketball games. The aim of the present study was to identify their predictors of success related to time, space, players, and tasks performed. The sample was composed of 818 ball screens corresponding to 20 close games (mean differences in score of 3.1 ± 0.8 points) randomly selected from the playoff games of the Spanish Basketball League (2008–2011). Classification tree analysis (CHAID) was used to analyse which variable or combination of variables, better predicts effectiveness during ball screens. The main results allowed identifying interactions with dribbler actions after the screen and the orientation of the screen on the ball. The results showed no interaction with game quarter and quarter minute temporal-related variables in both analyses. The present findings allow improving coaches’ strategic plans that involve selecting the most appropriate offensive approach when performing ball screens.  相似文献   

Kinematic,kinetic and EMG analysis of four front crawl flip turn techniques     

Suzana Matheus Pereira  Caroline Ruschel  Marcel Hubert  Leandro Machado  Helio Roesler  Ricardo Jorge Fernandes 《Journal of sports sciences》2015,33(19):2006-2015

This study aimed to analyse the kinematic, kinetic and electromyographic characteristics of four front crawl flip turn technique variants. The variants distinguished from each other by differences in body position (i.e. dorsal, lateral, ventral) during rolling, wall support, pushing and gliding phases. Seventeen highly trained swimmers (17.9 ± 3.2 years old) participated in interventional sessions and performed three trials of each variant, being monitored with a 3-D video system, a force platform and an electromyography (EMG) system. Studied variables: rolling time and distance, wall support time, push-off time, peak force and horizontal impulse at wall support and push-off, centre of mass horizontal velocity at the end of the push-off, gliding time, centre of mass depth, distance, average and final velocity during gliding, total turn time and electrical activity of Gastrocnemius Medialis, Tibialis Anterior, Biceps Femoris and Vastus Lateralis muscles. Depending on the variant, total turn time ranged from 2.37 ± 0.32 to 2.43 ± 0.33 s, push-off force from 1.86 ± 0.33 to 1.92 ± 0.26 BW and centre of mass velocity during gliding from 1.78 ± 0.21 to 1.94 ± 0.22 m · s^?1. The variants were not distinguishable in terms of kinematical, kinetic and EMG parameters during the rolling, wall support, pushing and gliding phases.  相似文献   

Revisiting Cross-document Structure Theory for multi-document discourse parsing     

Erick Galani Maziero  Maria Lucía del Rosário Castro Jorge  Thiago Alexandre Salgueiro Pardo 《Information processing & management》2014

Multi-document discourse parsing aims to automatically identify the relations among textual spans from different texts on the same topic. Recently, with the growing amount of information and the emergence of new technologies that deal with many sources of information, more precise and efficient parsing techniques are required. The most relevant theory to multi-document relationship, Cross-document Structure Theory (CST), has been used for parsing purposes before, though the results had not been satisfactory. CST has received many critics because of its subjectivity, which may lead to low annotation agreement and, consequently, to poor parsing performance. In this work, we propose a refinement of the original CST, which consists in (i) formalizing the relationship definitions, (ii) pruning and combining some relations based on their meaning, and (iii) organizing the relations in a hierarchical structure. The hypothesis for this refinement is that it will lead to better agreement in the annotation and consequently to better parsing results. For this aim, it was built an annotated corpus according to this refinement and it was observed an improvement in the annotation agreement. Based on this corpus, a parser was developed using machine learning techniques and hand-crafted rules. Specifically, hierarchical techniques were used to capture the hierarchical organization of the relations according to the proposed refinement of CST. These two approaches were used to identify the relations among texts spans and to generate multi-document annotation structure. Results outperformed other CST parsers, showing the adequacy of the proposed refinement in the theory.  相似文献   

Playing for freedom: Sócrates,futebol-arte and democratic struggle in Brazil     

Jorge Knijnik 《Soccer & Society》2014,15(5):635-654

Brazilian futebol has provided the world with several first-class players who have left their footprint on football history. However, no player can be compared to Sócrates; Sócrates was not only an icon of futebol-arte who mastered the ‘back heel’ and played for the Brazilian team in two FIFA World Cups (1982 and 1986), he was also a political activist who fought for democracy from inside the football world and who joined the Brazilian struggle for civil liberties during the 1980s. Interviews with sport journalists, an exploration of my personal memories of Brazilian futebol and the political scene, and a revisiting of Sócrates’ chronicles and testimonies together demonstrate Sócrates’ belief that the futebol arena was a privileged place to fight for social change. Sócrates passed away in 2011, leaving an inspiring heritage of joy, futebol-arte and freedom struggle. His libertarian legacy must be acknowledged in a country where, despite being acclaimed as one of the most authentic cultural expressions of the people, futebol is controlled by a corrupted and authoritarian elite.  相似文献   

Growth influences biomechanical profile of talented swimmers during the summer break     

Marc F. Moreira  Jorge E. Morais  Daniel A. Marinho  António J. Silva  Tiago M. Barbosa 《Sports biomechanics / International Society of Biomechanics in Sports》2014,13(1):62-74

This study aimed to analyse the effect of growth during a summer break on biomechanical profile of talented swimmers. Twenty-five young swimmers (12 boys and 13 girls) undertook several anthropometric and biomechanical tests at the end of the 2011–2012 season (pre-test) and 10 weeks later at the beginning of the 2012–2013 season (post-test). Height, arm span, hand surface area, and foot surface area were collected as anthropometric parameters, while stroke frequency, stroke length, stroke index, propelling efficiency, active drag, and active drag coefficient were considered as biomechanical variables. The mean swimming velocity during an all-out 25 m front crawl effort was used as the performance outcome. After the 10-week break, the swimmers were taller with an increased arm span, hand, and foot areas. Increases in stroke length, stroke index, propelling efficiency, and performance were also observed. Conversely, the stroke frequency, active drag, and drag coefficient remained unchanged. When controlling the effect of growth, no significant variation was determined on the biomechanical variables. The performance presented high associations with biomechanical and anthropometric parameters at pre-test and post-test, respectively. The results show that young talented swimmers still present biomechanical improvements after a 10-week break, which are mainly explained by their normal growth.  相似文献   

Match analysis in football: a systematic review     

Hugo Sarmento  Rui Marcelino  M. Teresa Anguera  Jorge CampaniÇo  Nuno Matos  José Carlos LeitÃo 《Journal of sports sciences》2014,32(20):1831-1843

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The role of preparatory heart rate deceleration on balance beam performance     

Cottyn J  de Clercq D  Crombez G  Lenoir M 《运动与训练心理学杂志》2008,30(2):159-170

Preparatory heart rate deceleration occurs in tasks with an external focus of attention and is often assumed to facilitate balance performance. However, its effects upon sport-related complex balance movements have not been studied. Heart rate patterns during the preparation period of an acrobatic element (flic-flac) on the balance beam were studied in 14 female gymnasts (M age 13.2 years). A significant heart rate deceleration was found in attempts with a fall in the consecutive acrobatic element, but not in attempts without a fall. These data suggest that preparatory heart rate deceleration may be detrimental to the performance of complex movements on the balance beam.  相似文献   

Effects of AM3 (Inmunoferon) on increased serum concentrations of interleukin-6 and tumour necrosis factor receptors I and II in cyclists     

Cordova A  Monserrat J  Villa G  Reyes E  Soto MA 《Journal of sports sciences》2006,24(6):565-573

The aims of this study were to examine the changes in plasma concentrations of inflammatory cytokines induced by training and competition in professional cyclists. We report the serum concentrations of interleukin-6 (IL-6), tumour necrosis factor alpha (TNF-a), tumour necrosis factor receptors I and II (TNFR-I and -II) in a prospective, randomized, double-blind trial involving the administration of AM3 (Inmunoferon), an oral booster immunomodulator, or placebo to 16 professional cyclists (n = 8 in each group) for 65 consecutive days. Serum was collected just before treatment began (baseline), at the end of pre-competition training, before the mountain stage of the competition (60 days), 4 h after finishing this stage (62 days), and 18 h after the fifth and last day of competition (65 days). To determine the normal levels of cytokines and soluble TNF receptors, individual samples from 14 moderately trained healthy controls were studied. After 60 days of training, the serum concentrations of IL-6 did not differ significantly from those at the beginning of the study for either group of cyclists (placebo and AM3). A significant rise was seen in IL-6 concentrations in both the AM3 and placebo groups at 62 days, 4 h after finishing the mountain stage. The increase was significantly greater in the placebo group than in the AM3 group. At 65 days of treatment, 18 h after the fifth and last day of competition, IL-6 concentrations were similar to those recorded at the end of the training, but were significantly higher in the placebo group than in the AM3 group. At the end of training, serum TNFR-I concentrations in both groups of cyclists were significantly lower than at baseline. The concentrations of serum TNFR-I and -II both 4 h after finishing the mountain stage and 18 h after the fifth and last day of competition were significantly higher than those recorded after training in both groups. Professional cycling competition is associated with increases in serum IL-6 and TNFR-I and -II concentrations. Inmunoferon treatment reduced significantly the concentrations of IL-6 but not those of TNFR-I and -II.  相似文献   

Agreement in activity energy expenditure assessed by accelerometer and self-report in adolescents: variation by sex, age, and weight status     

Machado-Rodrigues AM  Coelho-E-Silva MJ  Mota J  Cyrino E  Cumming SP  Riddoch C  Beunen G  Malina RM 《Journal of sports sciences》2011,29(14):1503-1514

The agreement between self-reported and objective estimates of activity energy expenditure was evaluated in adolescents by age, sex, and weight status. Altogether, 403 participants (217 females, 186 males) aged 13-16 years completed a 3-day physical activity diary and wore a GT1M accelerometer on the same days. Partial correlations (controlling for body mass) were used to determine associations between estimated activity energy expenditure (kcal · min(-1)) from the diary and accelerometry. Differences in the magnitude of the correlations were examined using Fisher's r to z transformations. Bland-Altman procedures were used to determine concordance between the self-reported and objective estimates. Partial correlations between assessments of activity energy expenditure (kcal · min(-1)) did not differ significantly by age (13-14 years: r = 0.41; 15-16 years: r = 0.42) or weight status (normal weight: r = 0.42; overweight: r = 0.39). The magnitude of the association was significantly affected by sex (Δr = 0.11; P < 0.05). The agreement was significantly higher in males than in females. The relationship between activity energy expenditure assessed by the objective method and the 3-day diary was moderate (controlling for weight, correlations ranged between 0.33 and 0.44). However, the 3-day diary revealed less agreement in specific group analyses; it markedly underestimated activity energy expenditure in overweight/obese and older adolescents. The assessment of activity energy expenditure is complex and may require a combination of methods.  相似文献   

Scaffolding in immersive virtual reality environments for learning English: an eye tracking study     

Bacca-Acosta  Jorge  Tejada  Julian  Fabregat  Ramon  Kinshuk  Guevara  Juan 《Educational technology research and development : ETR & D》2022,70(1):339-362

Educational technology research and development - Scaffolding is a mechanism for helping novice learners to solve a problem or complete a task that is beyond their current skill set. Prior research...  相似文献