557 research outputs found
Identification of key somatic features that are common and the ones that differ between swim strokes through allometric modeling
The aim of this study was to explore which key somatic features are common to four swim strokes and medley, and specifically to identify which characteristics benefit only specific strokes. Methods: The sample was composed of 130 swimmers (95 males aged 19.5 ± 2.9 years and 35 females aged 18.4 ± 2.8 years). A set of anthropometric variables was used to predict swimming speed in the four swimming strokes and medley. Results: A multiplicative model with allometric body size components was used to identify the demographic and anthropometric predictors of swimming speed. Trunk height and waist circumference were the only variables significantly different among swimming strokes (p < 0.05). Associations between swimming speed and arm length were similar in breaststroke and medley, and in freestyle, backstroke and butterfly (R2 = 60.9%). The model retained as swimming speed predictors the age2, upper body circumference, hand breadth, waist circumference, and subscapular skinfold thickness (these last two had negative associations). Conclusion: All these predictors were common to all four swim strokes and medley. Arm length was also retained as a significant predictor, but this one varied significantly between the four different swim strokes and medley. These findings highlight the importance of having a âV-shapeâ trunk, longer upper limbs, and large hands as predictors of swimming performanceNG and JM were supported by National Funds (FCTâPortuguese Foundation for Science and Technology) under the project UIDB/DTP/04045/2020.info:eu-repo/semantics/publishedVersio
Agreement between different methods to measure the active drag coefficient in front-crawl swimming
The aim of this study was to analyze the agreement of the active drag coefficient measured through drag and
propulsion methods. The sample was composed of 18 swimmers (nine boys: 15.9 ± 0.9 years; nine girls: 15.3 ± 1.2 years)
recruited from a national swimming team. The velocity perturbation method was used as the drag measurement system
and the Aquanex system as the propulsion system. For both sexes combined, the frontal surface area was 0.1128 ± 0.016
m2, swim velocity 1.54 ± 0.13 mâs-1, active drag 62.81 ± 11.37 N, propulsion 68.81 ± 12.41 N. The level of the active drag
coefficient agreement was calculated based on the mean values comparison, simple linear regression, and Bland Altman
plots. The mean data comparison revealed non-significant differences (p > 0.05) between methods to measure the active
drag coefficient. Both the linear regression (R2 = 0.82, p < 0.001) and Bland Altman plots revealed a very high agreement.
The active drag coefficient should be the main outcome used in the interpretation of the swimmersâ hydrodynamic profile,
because it is less sensitive to swimming velocity. Coaches and researchers should be aware that the active drag coefficient
can also be calculated based on propulsion methods and not just based on drag methods. Thus, the swimming community
can now use different equipment to measure the hydrodynamics of their swimmersThis work was supported by national funds (FCT - Portuguese Foundation for Science
and Technology) under the project UIDB/DTP/04045/2020info:eu-repo/semantics/publishedVersio
13th FINA WORLD CHAMPIONSHIP FINALS: STROKE KINEMATICS AND RACE TIMES ACCORDING TO PERFORMANCE, GENDER AND EVENT
The aim of this work was to compare the stroke kinematics and race times of the freestyle final races at the 13th FINA World Championships between: (i) the three medalists versus the last three finalists; (ii) males versus female swimmers; (iii) all events in each gender. Data was collected from the champioships official web site. There were no significant differences in the stroke kinematics neither in the race times between medallists and non-medallists. There were significant effects in the stroke kinematics and race times according to race event. There were significant effects in the stroke kinematics and race times according to swimmers gender. It seems there are different tactics and biomechanical strategies according to gender and swimming event
First-order phase transition in a 2D random-field Ising model with conflicting dynamics
The effects of locally random magnetic fields are considered in a
nonequilibrium Ising model defined on a square lattice with nearest-neighbors
interactions. In order to generate the random magnetic fields, we have
considered random variables that change randomly with time according to
a double-gaussian probability distribution, which consists of two single
gaussian distributions, centered at and , with the same width
. This distribution is very general, and can recover in appropriate
limits the bimodal distribution () and the single gaussian one
(). We performed Monte Carlo simulations in lattices with linear sizes in
the range . The system exhibits ferromagnetic and paramagnetic
steady states. Our results suggest the occurence of first-order phase
transitions between the above-mentioned phases at low temperatures and large
random-field intensities , for some small values of the width .
By means of finite size scaling, we estimate the critical exponents in the
low-field region, where we have continuous phase transitions. In addition, we
show a sketch of the phase diagram of the model for some values of .Comment: 13 pages, 9 figures, accepted for publication in JSTA
Evolving SPIDe Towards the Integration of Requirements Elicitation in Interaction Design
Among the various interaction (re)design processes and approaches, SPIDe is a semio-participatory
methodological process inspired by communication-centered design. However, the development of computational
solutions is not limited to interaction design. Requirements elicitation is also an integral part of this process. Some
SPIDe studies indicated that it is also possible to raise requirements through its application due to its participatory
characteristics. This article presents an investigation on the feasibility of SPIDe when applied to requirements elic itation integrated with interaction design, presenting an exploratory case study. From the perspective of different
experts, we explain the strengths and needs of SPIDe in supporting requirements elicitation integrated into inter action design. Data were collected through logbooks, semi-structured interviews, and the TAM questionnaire and
then analyzed through thematic analysis. The results show that the SPIDe use for requirements elicitation integrated
into the interaction design is feasible. Furthermore, they indicated that possible improvements in SPIDe could ben efit the development of the computational solutions considering a single application of SPIDe to obtain data for
interaction design and requirements elicitation integrated.info:eu-repo/semantics/publishedVersio
THE RELATIONSHIP BETWEEN FRONT CRAWL PERFORMANCE AND HYDRODYNAMICS IN YOUNG FEMALE SWIMMERS
The aim of this study was to analyse the relationship between front crawl performance and hydrodynamic variables during leg kicking. Sixteen female swimmers (9.2±0.6 years) participated in this study. The 200m front crawl performance, the 200m front crawl kicking performance and the active drag during leg kicking were measured. The velocity perturbation method was used to determine active drag. The 200m front crawl performance was significantly correlated with performance in 200m kicking (0.89), with hydrodynamic drag force during leg kicking (-0.70), and power output in kicking (-0.64). Drag coefficient was not related to the performance in 200 m front crawl. These findings underline the importance of leg kicking to performance in front crawl swimming in these ages and suggests the important role of kicking tasks during training in young swimmers
A MECHANICAL SPEEDO-METER TO ASSESS SWIMMERâS HORIZONTAL INTRA-CYCLIC VELOCITY: VALIDATION FOR BREASTSTROKE AND BUTTERFLY STROKE
The aim was to validate a system to assess speed-fluctuation at breaststroke and butterfly stroke. 12 boys and 11 undertook a set of maximal 2x25 m swims (Breaststroke and Butterfly stroke). The speedo-meter cable was attached to the subjectâs hip and data was acquired on-line. At the same time, subjects were recorded in the sagital plane with an underwater video camera enabling the hip to be digitized. The following were analysed: (i) maximal velocity; (ii) minimal velocity; (iii) difference between maximal and minimal velocity; (iv) coefficient of variation. There were no significant differences for the mean values between methods, except for the coefficient of variation. Linear regression models were highly related. More than 80% of the Bland-Altman plots were within the 1.96 standard-deviation criteria used as a rule of thumb for technique validation
Sensitivity and validity of a functional test for agility performance in water polo players
The aim of this study was to evaluate the sensitivity and validity of the Functional Test for Agility Performance (FTAP) in water polo players. Six elite junior (aged 16.33±0.82 years) male players and 65
competitive men (aged 18.1±4.3 years) who were classified in three groups (G1-3), participated in different phases of the test. The scores accomplished in FTAP at two periods (initial and final) were compared. They were correlated with the scores in Sprint/Agility Test and differences between standards of competition (G1-3) were assessed. Performance differences were assessed using the paired t-test and Pearsonâs correlation was used to determine the association with agility time in the Speed/Agility Test. Differences between standards of competition were assessed using ANOVA. The final Functional Test for Agility Performance was performed in fewer seconds compared to initial (p=.002, r=.94). No significant correlation was found between Functional Test for Agility Performance and Speed/Agility Test (r=.42, p=.40), as expected and
evidencing the discriminant validity. Differences were found between G1 and G3 (p<.001) and G2 and G3 (p=.008). The Functional Test for Agility Performance showed adequate sensitivity and validity, and thus is a decision-making test that can be used to assess training and expertise
CONCENTRATION OF SALIVARY CORTISOL AND TESTOSTERONE IN ELITE WOMEN FOOTBALL PLAYERS: ANALYSIS OF PERFORMANCE IN OFFICIAL MATCHES
This study aims to evaluate the relation between salivary concentrations of cortisol (C), testosterone (T), the ratio T:C and the individual performance of top-level female soccer athletes during official matches. Eighteen female athletes from a national soccer team (age 23.06 ± 4.33 years) participated in the study. Four official matches were analysed and the on-field time of each player as well as the index of individual effectiveness were calculated. Players were classified in two clusters according to their individual performance (cluster 1 â poor individual performance; cluster 2 â good individual performance) using K-means and their hormonal variables were compared. The players of cluster 2 generally revealed higher values (pË.05) in both the positive actions and individual effectiveness, when compared with the players of cluster 1. The players of both clusters presented identical values of C, T and T:C at the four evaluated matches. The athletes of cluster 2 showed a significant increase in C (pË.05) and a significant decrease in T and T:C before the games lost (M2 and M5). However, there was no linear relation between the variation of both hormones during the matches and the individual performance of players. Performance in competition revealed significant differences between players, though with no apparent relation to the hormonal kinetics of C and T before and after the matches
Wireless power transmission: R&D activities within Europe
Wireless power transmission (WPT) is an emerging technology that is gaining increased visibility in recent years. Efficient WPT circuits, systems and strategies can address a large group of applications spanning from batteryless systems, battery-free sensors, passive RF identification, near-field communications, and many others. WPT is a fundamental enabling technology of the Internet of Things concept, as well as machine-to-machine communications, since it minimizes the use of batteries and eliminates wired power connections. WPT technology brings together RF and dc circuit and system designers with different backgrounds on circuit design, novel materials and applications, and regulatory issues, forming a cross disciplinary team in order to achieve an efficient transmission of power over the air interface. This paper aims to present WPT technology in an integrated way, addressing state-of-the-art and challenges, and to discuss future R&D perspectives summarizing recent activities in Europe.The work of N. Borges Carvalho and A. J. S. Soares Boaventura was supported by the Portuguese Foundation for Science and Technology (FCT) under Project CREATION EXCL/EEI-TEL/0067/2012 and Doctoral Scholarship SFRH/BD/80615/2011. The work of H. Rogier was supported by BELSPO through the IAP Phase VII BESTCOM project and the Fund for Scientific Research-Flanders (FWO-V). The work of A. Georgiadis and A. Collado was supported by the European Union (EU) under Marie Curie FP7-PEOPLE-2009-IAPP 251557 and the Spanish Ministry of Economy and Competitiveness Project TEC 2012-39143. The work of J. A. GarcĂa and M. N. RuĂz was supported by the Spanish Ministries MICINN and MINECO under FEDER co-funded Project TEC2011-29126-C03-01 and Project CSD2008-00068. The work of J. Kracek and M. Mazanek was supported in part by the Czech Ministry of Education Youth and Sports under Project OC09075âNovel Emerging Wireless Systems
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