Maximal strength and power, muscle mass, endurance and serum hormones in weightlifters and road cyclists   总被引：1，自引：0，他引：1  

Izquierdo M  Ibáñez J  Häkkinen K  Kraemer WJ  Ruesta M  Gorostiaga EM 《Journal of sports sciences》2004,22(5):465-478

Maximal strength, power, muscle cross-sectional area, maximal and submaximal cycling endurance characteristics and serum hormone concentrations of testosterone, free testosterone and cortisol were examined in three groups of men: weightlifters (n = 11), amateur road cyclists (n = 18) and age-matched controls (n = 12). Weightlifters showed 45-55% higher power values than road cyclists and controls, whereas the differences in maximal strength and muscle mass were only 15% and 20%, respectively. These differences were maintained when average power output was expressed relative to body mass or relative to muscle cross-sectional area. Road cyclists recorded 44% higher maximal workloads, whereas submaximal blood lactate concentration was 50-55% lower with increasing workload than in controls and weightlifters. In road cyclists, workloads associated with blood lactate concentrations of 2 and 4 mmol.l-1 were 50-60% higher and occurred at a higher percentage of maximal workload than in weightlifters or controls. Basal serum total testosterone and free testosterone concentrations were lower in elite amateur cyclists than in age-matched weightlifters or untrained individuals. Significant negative correlations were noted between the individual values of maximal workload, workloads at 2 and 4 mmol.l-1 and the individual values of muscle power output (r = -0.37 to -0.49), as well as the individual basal values of serum total testosterone and free testosterone (r = -0.39 to -0.41). These results indicate that the specific status of the participants with respect to training, resistance or endurance is important for the magnitude of the neuromuscular, physiological and performance differences observed between weightlifters and road cyclists. The results suggest that, in cycling, long-term endurance training may interfere more with the development of muscle power than with the development of maximal strength, probably mediated by long-term cycling-related impairment in anabolic hormonal status.  相似文献   

La Roja: A Journey Through Spanish Football     

Francisco Javier Lopez Frías 《Soccer & Society》2015,16(1):149-151

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Influence of different sports on bone mass in growing girls     

Esther Ubago-Guisado  Alba Gómez-Cabello  Javier Sánchez-Sánchez  Jorge García-Unanue  Leonor Gallardo 《Journal of sports sciences》2015,33(16):1710-1718

The aim of this study was to analyse whether there are differences in bone mass in girls playing different sports. Two hundred girls (10.6 ± 1.5 years old, Tanner stages I–III) participated in the study and were divided into groups of 40 (swimmers, soccer players, basketball players, handball players and controls). Bone mineral content and bone mineral density (BMD) (whole body and hip) were measured using dual-energy X-ray absorptiometry. The degree of sexual development was determined using Tanner test, and physical activity habits were recorded through a questionnaire designed ad hoc for this research. Girls were divided by pubertal stage and the type of sport. In the prepubertal group, intertrochanteric BMD was significantly higher in both handball and soccer players compared with the control group (P < 0.05). Furthermore, in the pubertal group, total BMD, mean arms BMD, pelvis BMD, femoral neck BMD, intertrochanteric BMD and Ward’s triangle BMD were significantly higher in soccer and handball players compared with the control group (P < 0.05), and the swimmers showed significantly higher values in the mean arms BMD compared with the control group (P < 0.01). Our data suggest that sport practice during puberty, especially in activities that support the body weight, may be an important factor in achieving a high peak bone mass and improving bone health in girls.  相似文献   

Improving Chilean In-service Elementary Teachers’ Understanding of Nature of Science Using Self-contained NOS and Content-Embedded Mini-Courses     

Hernán Cofré  Claudia Vergara  Norman G. Lederman  Judith S. Lederman  David Santibáñez  Javier Jiménez  Macarena Yancovic 《Journal of Science Teacher Education》2014,25(7):759-783

Understanding nature of science (NOS) is considered critical to the development of students’ scientific literacy. However, various studies have shown that a large number of elementary and secondary science teachers do not possess an adequate understanding of NOS. This study investigated how elementary teachers’ understanding of NOS was impacted through a 1-year professional development program in Chile that included NOS instruction as a theme throughout two types of mini-courses in the program. Twelve teachers attended a 1-year development program focused on improving teacher content knowledge and included the instruction of NOS embedded in two self-contained NOS mini-courses (36 h) and two lessons (3 h each) within five science content mini-courses (30 h). The Views of NOS (version D+) questionnaire and interviews were used to assess teachers’ understanding of NOS at the beginning (January) and end of the program (December). Elementary teachers’ understanding of the creative, inferential, and tentative aspect of NOS showed improvement. According to the teachers’ perceptions, the most significant activities for improving their NOS understanding were decontextualized activities in both types of mini-courses (self-contained NOS and science content mini-courses). The implications for professional development programs are also discussed.  相似文献   

Seeing Change in Time: Video Games to Teach about Temporal Change in Scientific Phenomena     

Javier Corredor  Matthew Gaydos  Kurt Squire 《Journal of Science Education and Technology》2014,23(3):324-343

This article explores how learning biological concepts can be facilitated by playing a video game that depicts interactions and processes at the subcellular level. Particularly, this article reviews the effects of a real-time strategy game that requires players to control the behavior of a virus and interact with cell structures in a way that resembles the actual behavior of biological agents. The evaluation of the video game presented here aims at showing that video games have representational advantages that facilitate the construction of dynamic mental models. Ultimately, the article shows that when video game’s characteristics come in contact with expert knowledge during game design, the game becomes an excellent medium for supporting the learning of disciplinary content related to dynamic processes. In particular, results show that students who participated in a game-based intervention aimed at teaching biology described a higher number of temporal-dependent interactions as measured by the coding of verbal protocols and drawings than students who used texts and diagrams to learn the same topic.  相似文献   

Determinants of the Web accessibility of European banks     

Ana B. Martínez  Javier De Andrés  Julita García 《Information processing & management》2014

This paper aims at identifying the factors influencing the implementation of Web accessibility (WA) by European banks. We studied a database made up of 49 European banks whose shares are included in the Dow Jones EURO STOXX® TMI Banks [8300] Index. Regarding the factors for the implementation, we considered three feasible reasons. Firstly, WA adoption can be motivated by operational factors, as WA can aid in increasing operational efficiency. Secondly, we expect large banks to have higher WA levels, as small firms face competitive disadvantages with regard to technology adoption. Lastly, WA can also be understood as a part of the Corporate Social Responsibility (CSR) strategy, so, the more committed a bank is to CSR, the more prone it will be to implement WA. Our results indicate that neither the operational factors nor the firm size seem to have exerted a significant influence on WA adoption. Regarding CSR commitment, results indicate a significant influence on WA adoption. However, the effect of the influence is contrary to that hypothesized, since more CSR-committed banks have less accessible Web sites. A possible reason for this result is that banks not included in the CSR indexes try to overcome this drawback by engaging in alternative CSR activities such as WA.  相似文献   

Development of a three-dimensional cell culture system based on microfluidics for nuclear magnetic resonance and optical monitoring     

Vicent Esteve  Javier Berganzo  Rosa Monge  M. Carmen Martínez-Bisbal  Rosa Villa  Bernardo Celda  Luis Fernandez 《Biomicrofluidics》2014,8(6)

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Anticipatory strategies of team-handball goalkeepers     

Gutierrez-Davila M  Rojas FJ  Ortega M  Campos J  Parraga J 《Journal of sports sciences》2011,29(12):1321-1328

This study seeks to discover whether handball goalkeepers employ a general anticipatory strategy when facing long distance throws and the effect of uncertainty on these strategies. Seven goalkeepers and four throwers took part. We used a force platform to analyse the goalkeeper's movements on the basis of reaction forces and two video cameras synchronised at 500 Hz to film the throw using 3D video techniques. The goalkeepers initiated their movement towards the side of the throw 193 ± 67 ms before the release of the ball and when the uncertainty was reduced the time increased to 349 ± 71 ms. The kinematics analysis of their centre of mass indicated that there was an anticipatory strategy of movement with certain modifications when there was greater uncertainty. All the average scores referring to velocity and lateral movement of the goalkeeper's centre of mass are significantly greater than those recorded for the experimental situation with bigger uncertainty. The methodology used has enabled us to tackle the study of anticipation from an analysis of the movement used by goalkeepers to save the ball.  相似文献   

Summation and transfer of negative occasion setting     

Javier R. Morell  Peter C. Holland 《Learning & behavior》1993,21(2):145-153

Two experiments examined the summation and transfer of negative occasion setting in serial feature negative (X→A?/A+) and negative patterning discriminations (X→A?/X+/A+) in a discrete-trial operant task with rats. With both discrimination procedures, negative occasion setting transferred readily (but not perfectly) to cues trained as targets in another similar discrimination procedure, but not to cues that were separately trained. Furthermore, with both discrimination procedures, the negative occasion-setting powers of features from two individual discriminations summed, both when those features were trained with the same targets and when they were trained with different targets. After negative patterning discriminations, in which the feature (X) cues were separately reinforced, this summation of negative occasion setting occurred despite the concomitant summation of the features’ excitatory control in the absence of an explicit target cue. These data, which replicated and extended previously reported data from Pavlovian feature negative procedures, are discussed in the context of hierarchical, generalization, and network models of discrimination learning.  相似文献   

Young people in the argentine education system: Their inclusion and exclusion     

Guillermina Tiramonti  Inés Dussel  Javier Hermo 《Prospects》1995,25(3):481-493

Graduate in political sciences, University of El Salvador. Post-graduate in education and society, Facultad Latinoamericana de Ciencias Sociales (FLACSO, Argentina). Co-ordinator for education and society, post-graduate professor of education and society and of the diploma in social sciences (educational management) for FLACSO. Invited post-graduate professor at the University of Bologna. Consultant to the OEI, CEPAL and INAP. Professor of educational policy at the National University of La Plata. Editor of the reviewPropuesta educativa [Educational offer].  相似文献