Eccentric flywheel post-activation potentiation influences swimming start performance kinetics

This study aimed to assess the effects of post-activation potentiation in the strength related variables of a kick start. Thirteen competitive swimmers performed three kick starts after a standardized warm up (denoted USUAL) and another after inducing post-activation through five isotonic repetitions on an eccentric flywheel (denoted PAP). A T-test was used to quantify differences between USUAL and PAP warm up. The best trial of each subject achieved by natural conditions (denoted PEAK) was compared with data obtained after PAP. An instrumented starting block with independent triaxial force plates, collected the strength variables related with the impulse at take off. Improvements in the vertical components of force were observed after PAP compared with USUAL, meanwhile no differences were detected on the horizontal components of it. The velocity at take off was higher after PAP compared with USUAL (4.32 ± 0.88 vs 3.93 ± 0.60 m*s-1; p = 0.02). No differences in force or velocity were detected comparing PAP with PEAK (4.13 ± 0.62 m*s-1, p = 0.11). The PAP warm-up increased vertical force and it was transferred to a higher resultant velocity at take-off. This improvement would equal the best result possible obtained in natural conditions after some trials.     

Metaphonological abilities of Japanese children

Linguists generally conceive of speech as a sequence of elementary soundunits or phones. On the other hand, cognitive psychologists have established the existence of a close link between segmental awareness (SA) and alphabetic literacy: the best speech segmenters are also the best readers; conversely, the lack of SA leads to lagging in the acquisition of the written code. Studies carried out with illiterate adults and preliterate children suggest that SA does not arise outside the context of learning to read and write. Furthermore, cross-cultural studies have so far supported the hypothesis that SA is promoted by alphabetic literacy only, and not by logographic or syllabic literacy. The present study is inspired by Mann's (1986) research and aims at studying the phonological (i.e. syllabic and phonemic) analysis abilities of Japanese first-graders who are learning to read in a syllabic writing system. The relatively poor performance of subjects tends to confirm the starting hypothesis that SA is closely linked to alphabetic literacy. Moreover, the subjects apparently resorted to spelling-based strategies to accomplish the tasks presented. This comes to support the general idea that the written characters used to transcribe a language tend to exert a strong influence on the conscious perceptual representation of the phonology of this language.This study would not have been possible without the precious help of Miss T. Yamamoto for the construction of the experimental items. We are also much indebted to Mrs. A. M. Van Craen for her good advice and for having introduced one of us (Carmela Spagnoletti) to the Japanese School of Brussels. We also wish to thank the Director of the Japanese School of Brussels for his permission to carry out the experimental work with his pupils, and to all the professors for having invited the parents to cooperate and provided us with many useful information. We are especially grateful to the children who participated to the experinmental sessions as well as to their parents. The present work has been partially supported by the Belgian Fonds de la Recherche fondamentale collective (convention n° 2.4562.86) and the Ministry of scientific Policy (Action de Recherche concertée: Processus cognitifs dans la lecture).     

A comparison of the reverse and power punches in oriental martial arts

In this study, we compared mechanical factors in the reverse and three-inch power punches. Twelve expert male martial artists stood on a force plate, and executed reverse and power punches against a padded target fixed to a wall-mounted force plate. The force plates measured horizontal forces, and subsequently impulses and body centre of mass velocity changes. The motions of four markers attached to the arm were also collected, and were used to compute the horizontal velocities of the knuckle and of the arm centre of mass. The power punch produced smaller velocities immediately before impact than the reverse punch for the whole-body centre of mass (0.14 vs. 0.31 m x s(-1)), for the arm centre of mass (2.86 vs. 4.68 m x s(-1)), and for the knuckle (4.09 vs. 6.43 m x s(-1)). The peak force exerted by the fist was much smaller in the power punch than in the reverse punch (790 vs. 1450 N). However, the linear impulse exerted by the fist during the first 0.20 s of contact was slightly larger in the power punch than in the reverse punch (43.2 vs. 37.7 N x s). The results indicate that the power punch is less potent than the reverse punch, but slightly more effective for throwing the opponent off balance.     

Predicting centre of mass horizontal speed in low to severe swimming intensities with linear and non-linear models

We aimed to compare multilayer perceptron (MLP) neural networks, radial basis function neural networks (RBF) and linear models (LM) accuracy to predict the centre of mass (CM) horizontal speed at low-moderate, heavy and severe swimming intensities using physiological and biomechanical dataset. Ten trained male swimmers completed a 7 × 200 m front crawl protocol (0.05 m.s^?1 increments and 30 s intervals) to assess expiratory gases and blood lactate concentrations. Two surface and four underwater cameras recorded independent images subsequently processed focusing a three-dimensional reconstruction of two upper limb cycles at 25 and 175 m laps. Eight physiological and 13 biomechanical variables were inputted to predict CM horizontal speed. MLP, RBF and LM were implemented with the Levenberg-Marquardt algorithm (feed forward with a six-neuron hidden layer), orthogonal least squares algorithm and decomposition of matrices. MLP revealed higher prediction error than LM at low-moderate intensity (2.43 ± 1.44 and 1.67 ± 0.60%), MLP and RBF depicted lower mean absolute percentage errors than LM at heavy intensity (2.45 ± 1.61, 1.82 ± 0.92 and 3.72 ± 1.67%) and RBF neural networks registered lower errors than MLP and LM at severe intensity (2.78 ± 0.96, 3.89 ± 1.78 and 4.47 ± 2.36%). Artificial neural networks are suitable for speed model-fit at heavy and severe swimming intensities when considering physiological and biomechanical background.     

Analysis of doping control test results in individual and team sports from 2003 to 2015

Background:Determining the prevalence of doping in sport might be useful for anti-doping authorities to gauge the effectiveness of anti-doping policies implemented to prevent positive attitudes toward doping.Using questionnaires and personal interviews,previous investigations have found that the prevalence of doping might be different among different sports disciplines;however,there is no sport-specific information about the proportion of adverse and atypical findings(AAF) in samples used for doping control.The aim of the present investigation was to assess the differences in the frequency of adverse analytical and atypical findings among sports using the data made available by the World Anti-Doping Agency.Methods:The data included in this investigation were gathered from the Testing Figures Reports made available annually from 2003 to 2015 by the World Anti-Doping Agency.These Testing Figures Reports include information about the number of samples analyzed,the number of AAFs reported,and the most commonly found drugs in the urine and blood samples analyzed.A total of 1,347,213 samples were analyzed from the individual sports selected for this investigation,and 698,371 samples were analyzed for disciplines catalogued as team sports.Results:In individual sports,the highest proportions of AAF were 3.3%±1.0% in cycling,3.0%±0.6% in weightlifting,and 2.9%±0.6% in boxing.In team sports,the highest proportions of AAF were 2.2%±0.5% in ice hockey,2.0%±0.5% in rugby,and 2.0%±0.5% in basketball.Gymnastics and skating had the lowest proportions at(≤1.0%) for individual sports,and field hockey,volleyball and football had the lowest proportions for team sports(≤1.4%).Conclusion:As suggested by the analysis,the incidence of AAF was not uniform across all sports disciplines,with the different proportions pointing to an uneven use of banned substances depending on the sport.This information might be useful for increasing the strength and efficacy of anti-doping policies in those sports with the highest prevalence in the use of banned substances.     

Legitimating the world-class university concept through the discourse of elite universities’ presidents†

Although well-renowned universities attempt to differentiate themselves from other universities, little research has been undertaken on the principal themes involved in the concept of the world-class university (WCU) as presented in speeches by members of WCUs. These discourses are a key tool in universities’ attempt to shape the competitive framework of higher education through legitimacy. We study the presidents’ discourses from 100 leading universities to identify the themes and emergent discourse of these universities’ communities. Applying topic modeling methodology to the speeches’ corpus, we find seven communities (Worldwide-the four regions, American-from different states, Flagship, Education concerned, Some Chinese universities, Central European universities and Challengers) and four main themes arising from WCUs’ discourses (Research universities within international rankings, Stakeholders and leadership, Mission and values, and Education). Our preliminary findings suggest that leading universities are working to adopt the WCU label based on their salient characteristics.     

Optimal control for linear systems with time delay in control input

This paper presents the optimal regulator for a linear system with time delay in control input and a quadratic cost function. The optimal regulator equations are obtained using the duality principle, which is applied to the optimal filter for linear systems with time delay in observations, and then proved using the maximum principle. Performance of the obtained optimal regulator is verified in the illustrative example against the best linear regulator available for linear systems without delays. Simulation graphs and comparison tables demonstrating better performance of the obtained optimal regulator are included.     

Análisis evolutivo de la empatía y la ansiedad como variables mediadoras del comportamiento de ayuda

Resumen

En este trabajo se analizan los efectos de la empatía y la ansiedad sobre la conducta de ayuda. Las hipótesis intentan discriminar entre las diferentes motivaciones (altruistas o egoístas) que pueden suscitar la conducta de ayuda. Se realizaron dos estudios, uno con niños y otro con adolescentes. Los datos se analizaron con ecuaciones estructurales (Lisrel, VI). Los resultados mostraron diferencias evolutivas en cuanto a la capacidad de las condiciones experimentales para provocar empatía y ansiedad, y por lo tanto, para producir la conducta de ayuda. Como conclusión se propone la ampliación del modelo de Batson y Coke, dado el peso que ha mostrado tener la variable «empatia disposicional» para explicar la conducta de ayuda. Respecto al tipo de motivación que originó la ayuda cabe señalar que, en ambos estudios, la ayuda se explicó por la empatía (disposicional y situacional) por lo que podemos deducir que la motivación fue altruista.