Swimming and peak bone mineral density: A systematic review and meta-analysis     

Alejandro Gomez-Bruton  Jesús Montero-Marín  Alejandro González-Agüero  Alba Gómez-Cabello  Javier García-Campayo  Luis A. Moreno 《Journal of sports sciences》2018,36(4):365-377

This meta-analysis aims to determine the effects of regular swimming on bone mineral density (BMD) in young adults (18–30 years). A systematic search was performed in Pubmed, SPORTDiscus and the Cochrane Library from the earliest possible year to March 2016. Swimmers were compared to non-athletic controls (CG) and to high-impact athletes (HIGH). Effect sizes with the Hedges g in random effects models were developed. Fourteen studies met the inclusion criteria and were included in the meta-analyses. Swimmers presented similar BMD values to CG in whole-body (g = ?0.20; P = 0.251), femoral neck (g = ?0.05; P = 0.818) and lumbar spine (g = 0.18; P = 0.492); and lower BMD in the whole-body (g = ?1.21; P < 0.001), femoral neck (g = ?1.51; P < 0.001) and lumbar spine (g = ?0.84; P = 0.017) than the HIGH. For the whole-body differences, the higher the latitude the smaller the differences between swimmers and HIGH (B = 0.10; P = 0.001). For the femoral neck differences, age also seemed to reduce the differences between groups (B = 0.19; P = 0.020). Young adult swimmers present similar BMD values than CG and lower values than HIGH.  相似文献   

Effect of verbal instructions and image size on visual search strategies in basketball free throw shooting     

Saleh A. Al-Abood  Simon J. Bennett  Francisco Moreno Hernandez  Derek Ashford  Keith Davids 《Journal of sports sciences》2013,31(3):271-278

We assessed the effects on basketball free throw performance of two types of verbal directions with an external attentional focus. Novices ( n = 16) were pre-tested on free throw performance and assigned to two groups of similar ability ( n = 8 in each). Both groups received verbal instructions with an external focus on either movement dynamics (movement form) or movement effects (e.g. ball trajectory relative to basket). The participants also observed a skilled model performing the task on either a small or large screen monitor, to ascertain the effects of visual presentation mode on task performance. After observation of six videotaped trials, all participants were given a post-test. Visual search patterns were monitored during observation and cross-referenced with performance on the pre- and post-test. Group effects were noted for verbal instructions and image size on visual search strategies and free throw performance. The 'movement effects' group saw a significant improvement in outcome scores between the pre-test and post-test. These results supported evidence that this group spent more viewing time on information outside the body than the 'movement dynamics' group. Image size affected both groups equally with more fixations of shorter duration when viewing the small screen. The results support the benefits of instructions when observing a model with an external focus on movement effects, not dynamics.  相似文献   

Activity profile of top-class association football referees in relation to performance in selected physical tests     

Javier Mallo  José-María García-Aranda  Bart Gilis  Werner Helsen 《Journal of sports sciences》2013,31(7):805-813

Abstract

The aims of the present study were (1) to analyse the physical demands of top-class referees and (2) to compare their official FIFA fitness test results with physical performance during a match. The work rate profiles of 11 international referees were assessed during 12 competitive matches at the 2003 FIFA Under-17 World Cup and then analysed using a bi-dimensional photogrammetric video analysis system based on direct lineal transformation (DLT) algorithms. In the first 15 min of matches, the referees were more active, performing more high-intensity exercise (P < 0.01) than in the first 15 min of the second half. During the second half of matches, the referees covered a shorter distance (P < 0.01), spent more time standing still (P < 0.05), and covered less ground cruising (P < 0.05), sprinting (P < 0.05), and moving backwards (P < 0.001) than in the first half. Also in the second 45 min, the distance of referees from infringements increased (P < 0.05) in the left attacking zone of the filed. There was also a decrease (P < 0.05) in performance in the period following the most high-intensity activity, compared with the mean for the 90 min. Time spent performing high-intensity activities during a match was not related to performance in the 12-min run (r ² = 0.30; P < 0.05), the 200-m sprint (r ² = 0.05; P < 0.05), or the 50-m sprint (r ² = 0.001; P < 0.05). The results of this study show that: (1) top-class referees experienced fatigue at different stages of the match, and (2) the typical field tests used by FIFA (two 50-m and 200-m sprints, followed by a 12-min run) are not correlated with match activities.  相似文献   

Linking human,technological, and relational assets to technological innovation: exploring a new approach     

Castro  Gregorio Martín-de  Delgado-Verde  Miriam  Amores-Salvadó  Javier  Navas-López  José Emilio 《知识管理研究与实践》2013,11(2):123-132

In a knowledge-based economy, firms' technological innovations represent one of the best ways in order to survive and to achieve firm success. Nonaka and Takeuchi stated that technological innovation is close to firms' intellectual or knowledge asset management, and additional efforts are needed to understand these complex causal relationships. If we can assume that technological innovation causation rarely has a single cause, and that these causes rarely operate in isolation from each other, empirical research needs a new configurational perspective, where the integrity of firms' technological innovations as complex configurations of causal factors are preserved. This way, using a configurational approach, and primary data of 251 technology-based firms based in Spain, this paper explores firms' human, technological, and relational assets configurations and product innovations.

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Reliability and validity of different methods of estimating the one-repetition maximum during the free-weight prone bench pull exercise     

Amador García-Ramos  Paola Barboza-González  David Ulloa-Díaz  Angela Rodriguez-Perea  Darío Martinez-Garcia  Francisco Guede-Rojas 《Journal of sports sciences》2013,31(19):2205-2212

ABSTRACT

This study examined the reliability and validity of three methods of estimating the one-repetition maximum (1RM) during the free-weight prone bench pull exercise. Twenty-six men (22 rowers and four weightlifters) performed an incremental loading test until reaching their 1RM, followed by a set of repetitions-to-failure. Eighteen participants were re-tested to conduct the reliability analysis. The 1RM was estimated through the lifts-to-failure equations proposed by Lombardi and O’Connor, general load-velocity (L-V) relationships proposed by Sánchez-Medina and Loturco and the individual L-V relationships modelled using four (multiple-point method) or only two loads (two-point method). The direct method provided the highest reliability (coefficient of variation [CV] = 2.45% and intraclass correlation coefficient [ICC] = 0.97), followed by the Lombardi’s equation (CV = 3.44% and ICC = 0.94), and no meaningful differences were observed between the remaining methods (CV range = 4.95–6.89% and ICC range = 0.81–0.91). The lifts-to-failure equations overestimated the 1RM (3.43–4.08%), the general L-V relationship proposed by Sánchez-Medina underestimated the 1RM (?3.77%), and no significant differences were observed for the remaining prediction methods (?0.40–0.86%). The individual L-V relationship could be recommended as the most accurate method for predicting the 1RM during the free-weight prone bench pull exercise.  相似文献   

Changing attitudes and intentions related to doping: An analysis of individual differences in need for cognition     

Javier Horcajo  David Santos  Joshua J. Guyer  Lorena Moreno 《Journal of sports sciences》2013,31(24):2835-2843

ABSTRACT

Research has shown that athletes’ attitudes towards the use of banned performance-enhancing substances are reliable predictors of their intentions to use these substances, which in turn can be relevant predictors of their actual doping behaviours. Despite the important role played by attitudes and intentions in doping, research analysing how to change those attitudes and intentions is relatively scarce. The present study examined how individual differences in Need for Cognition (NC, Cacioppo & Petty, 1982) influenced doping-related attitude change and subsequent behavioural intentions. Participants were randomly assigned to read a persuasive message either against or in favour of legalising the use of several banned substances, including anabolic androgenic steroids (AAS) and Erythropoietin (EPO). In addition, participants completed the NC scale, and finally reported their attitudes and behavioural intentions regarding the legalisation proposal. As hypothesised, results showed that participants who received an anti-legalisation message had significantly more unfavourable attitudes towards the proposal than participants who received a pro-legalisation message, regardless of NC. However, as predicted, NC moderated the relationship between individuals’ attitudes and their intentions. That is, high-NC participants showed greater attitude-intention correspondence than low-NC participants.  相似文献   

Effect of the 3-Point Line Change on the Game Dynamics in Girls' Minibasketball     

José L. Arias  Francisco M. Argudo  José I. Alonso 《Research quarterly for exercise and sport》2013,84(3):502-509

We examined the game dynamics in minibasketball when comparing two different forms of the 3-point line. During the first competition, participants used a 3-point line delimited by the free-throw lane, and 1,642 ball possessions were recorded. During the second competition, participants played with a 3-point line delimited by a rectangular area, and 1,669 ball possessions were recorded. Results from the Mann-Whitney U Test show that when playing with a 3-point line delimited by the free-throw lane, higher average values were achieved in terms of points scored, number of players taking part in the ball possessions, number of passes, and one-on-one situations.  相似文献   

Variable training: effects on velocity and accuracy in the tennis serve     

Hector Hernández-Davo  Tomás Urbán  Jose Manuel Sarabia  Casto Juan-Recio  Francisco Javier Moreno 《Journal of sports sciences》2013,31(14):1383-1388

Abstract

Variable practice has been shown to be an effective strategy to improve open motor skills. However, the usefulness of this procedure in closed motor skills remains controversial. The following study has the objective of analysing the effects of variability practice in the improvement of a closed skill. The skill studied has been the tennis serve. Thirty young tennis players (13 ± 1.52 years), divided in two groups, took part in this study. One group practiced in variable conditions and the other group in consistency conditions. Both groups performed 12 training sessions (60 serves/session). The variable practice group improved their accuracy significantly compared with the consistency group (F_3.25 = 3.078; P = 0.035). The velocity of serve increased after training in both groups (F_3.25 = 15.890; P = 0.001). The practice in variable conditions seems to be effective in improving the performance of the tennis serve.  相似文献   

Providing metrics and automatic enhancement for hierarchical taxonomies     

Ghassan Beydoun  Francisco García-Sánchez  Cristin M. Vincent-Torres  Antonio A. Lopez-Lorca  Rodrigo Martínez-Béjar 《Information processing & management》2013

Taxonomies enable organising information in a human–machine understandable form, but constructing them for reuse and maintainability remains difficult. The paper presents a formal underpinning to provide quality metrics for a taxonomy under development. It proposes a methodology for semi-automatic building of maintainable taxonomies and outlines key features of the knowledge engineering context where the metrics and methodology are most suitable. The strength of the approach presented is that it is applied during the actual construction of the taxonomy. Users provide terms to describe different domain elements, as well as their attributes, and methodology uses metrics to assess the quality of this input. Changes according to given quality constraints are then proposed during the actual development of the taxonomy.  相似文献   

List of Reviewers     

Coral Falco  Javier Molina-García  Octavio Álvarez  Isaac Estevan 《Sports biomechanics / International Society of Biomechanics in Sports》2013,12(4):381-382

The aim of this study was to investigate the effects of target distance on temporal and impact force parameters that are important performance factors in taekwondo kicks. Forty-nine taekwondo athletes (age = 24.5 ± 5.9 years; mass = 79.9 ± 10.8 kg) were recruited: 13 male experts, 21 male novices, 8 female experts, and 6 female novices. Impact force, reaction time, and execution time were computed. Three-way repeated measure ANOVAs revealed significant ‘distance’ effect on impact force, reaction time, and execution time (p = 0.001). Comparisons between distance conditions revealed that taekwondo athletes kicked with higher impact force from short distance (17.6 ± 7.5 N/kg) than from long distance (13.1 ± 5.7 N/kg) (p < 0.001), had lower reaction time from short distance (498 ± 90 ms) and normal distance (521 ± 111 ms) than from long distance (602 ± 121 ms) (p < 0.001), and had lower execution time from short distance (261 ± 69 ms/m) than from normal distance (306 ± 105 ms/m) or from long distance (350 ± 106 ms/m) (p = 0.003 and p < 0.001, respectively). In conclusion, target distance affected the kick performance; as distance increases, impact force decreased and reaction time increased. Therefore, when reaction to a simple visual stimulus is needed, kicking from a long distance is not recommended, as longer time is required to respond.  相似文献