1,720,964 research outputs found
Underwater fly kick development in swimming using a skill-acquisition intervention: a pilot study
No full textWithin coach education programmes, training periodization focusses upon the manipulation of training intensity and volume with consideration to the physiological and physical loading experienced by the athlete. Swimming coaches tend to use targeted drills to develop skills, but these focus on short-term performance rather than longer-term learning, and do not have scientific grounding. The aim of this study was to assess the effects of a four-week intervention on underwater fly kick performance. Ethical approval was granted by the Faculty of Engineering and Physical Sciences at the University of Southampton. The intervention, based upon skill-acquisition frameworks, consisted of four key stages working through coordination, skill adaptability, movement variability and performance stability training. Potential interventions relating to each stage were collated and this library was provided to the swimming coach as a framework. Nine national level male participants attended two data collection sessions exactly four weeks apart. Ten reflective markers were placed on key bony land-marks, and a six camera Qualisys motion capture system (100 Hz) recorded kinematics. Within the intervention group, improved underwater fly kick performance was observed through increased average and peak horizontal swimming velocity (2%, P = 0.04 and 4%, P = 0.02 respectively). Kick frequency increased (11%, P = 0.00) and the kick became more symmetrical (4% decreased up-beat duration and 39% reduced difference between up and down-beat toe velocities, P = 0.02 and P = 0.00 respectively). Ankle range of motion reduced (P = 0.01) and peak knee extension increased (P = 0.00). The results indicate that the four-week intervention improved underwater fly kick performance, providing evidence for the structured implementation of skill training theory-driven practices in underwater fly kick coaching
Assessment of error levels across the domain of a three-dimensional underwater motion capture methodology
No full textAssessing human movement underwater presents many challenges, and it is therefore important to understand error across the whole capture domain to ensure accuracy in resulting kinematics. This study assessed the accuracy across the capture domain of a submerged motion capture methodology. Six Qualisys cameras created an underwater capture volume of 8x2x2m. Average error levels across the domain were acceptable in two uncertainty trials (1.23mm and 1.34mm), but error increased at the ends and top of the domain. By selecting an area of interest for assessment that excluded areas with lower accuracy, error was reduced to 0.53mm. This study highlights the need to investigate error levels across a motion capture domain, particularly when this is a large volume, to ensure results obtained from investigations are reliable
Two and three-dimensional assessments of lower-limb kinematics in underwater fly kick
No full textThe purpose of this study was to compare sagittal plane lower limb kinematics of underwater fly kick measured using two and three-dimensional methods. Eight male participants (average FINA points score 801±138) completed underwater fly kick trials, recorded using a six camera Qualisys underwater system. Each trial was analysed using both two and three-dimensional methods. Lower-limb angles were significantly underestimated using two-dimensional methods, particularly at the hip where flexion and range of motion reduced by 13.73 degrees and 15.91 degrees respectively. The ankle and hip produce a large amount motion in the transverse and frontal planes. The results of two-dimensional analyses of underwater fly kick should be interpreted with caution due reductions in measured angles, and exclusion of out-of-plane kinematic information
Error assessment of a three-dimensional underwater motion capture methodology
No full textMotion analysis technology is used in various settings to assess human kinematics. Assessing human movement underwater presents many challenges, making it important to understand measurement error associated with the setup and calibration of the system ensuring accuracy in resulting kinematics. This study assessed the accuracy across the entire domain of a submerged motion capture methodology. Six Qualisys cameras created an underwater capture volume of 6.9 × 2.1 × 2.1 m3. Average error levels were acceptable in four uncertainty trials (<± 5 mm error). By selecting an area of interest that excluded areas with low accuracy near domain borders, measurement error reduced by up to 0.13 mm, up to 1.27 mm lower than outside this area. Interpolated error indicated that intracyclic measurement error may alter measured kinematics by up to 13.80 mm, with error greater than 5 mm affecting over 50% of the kick cycle. Investigating error levels across the domain can inform researchers whether a recalibration is necessary or help to identify areas where high error levels would affect kinematics. This study highlights the need to investigate error levels across a motion capture domain, particularly when this is a large volume, to ensure results obtained from investigations are reliable
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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