1,721,107 research outputs found
Anaerobic alactic energy assessment in middle distance swimming.
No full textTo estimate the anaerobic alactic contribution in a 200 m middle distance swimming trial by means of two different methods based: (1) on the fast component of the {Mathematical expression} off-kinetics (Anarecovery) and (2) on the kinetics of maximal phosphocreatine splitting in the contracting muscle (Anapcr). Ten elite male swimmers performed a 200 m front crawl trial at maximal velocity during which {Mathematical expression}was directly measured using a telemetric portable gas analyser; during the recovery period {Mathematical expression} data were collected until baseline values were reached. No significant differences between the two methods were observed; mean ± SD values were 31.7 ± 2.5 and 32.6 ± 2.8 kJ, for Anapcr and Anarecovery, respectively. Despite the existence of some caveats regarding both methods for estimation of the anaerobic alactic contribution, data reported in this study indicate that both yield similar results and both allow to estimate this contribution in supra-maximal swimming trials. This has important implications on swimming energetics, since the non-inclusion of the anaerobic alactic contribution to total metabolic energy expenditure leads to an underestimation of the energy cost at supra-maximal speeds
An energy balance of the 200 m front crawl race.
No full textThe purpose of the present study was to determine the relative contribution of the aerobic (Aer), anaerobic lactic (AnL) and alactic (AnAl) energy sources during each of the four laps of a 200 m front crawl race. Additionally, energy cost (C) and arm stroke efficiency were also computed. Ten international swimmers performed a 200 m front crawl swim, as well as 50, 100, and 150 m at the 200 m pace. Oxygen consumption was measured during the 200 m swim and blood samples were collected before and after each swim; the C of swimming was calculated as the ratio of E (tot) to distance (where E (tot) = Aer + AnL + AnAl). Arm stroke efficiency was calculated by kinematic analysis as the speed of center of mass to the ratio of 3D hand speed. For the 200 m the contributions were 65.9\% (Aer), 13.6\% (AnL), and 20.4\% (AnAl) whereas for each lap they were 44.6, 73.2, 83.3 and 66.6\% (Aer), 14.1, 5.0, 4.4 and 28.1\% (AnL) and 41.3, 21.8, 12.3 and 5.2\% (AnAl) for the four laps, respectively. For the 200 m as a whole C was 1.60 kJ m(-1) whereas C = 1.71, 1.56, 1.44 and 1.70 kJ m(-1) for each consecutive lap, respectively. Arm stroke efficiency ranged from 0.40 to 0.43 and was significantly lower in the last lap as compared to the first (P = 0.002), suggesting the occurrence of fatigue. The decrease in arm stroke efficiency was mirrored by an increase in C as can be expected on theoretical grounds
Exercise modality effect on bioenergetical performance at VO2max intensity.
No full textPURPOSE: A bioenergetical analysis of different exercise modes near maximal oxygen consumption (VO2max) intensity is scarce, hampering the prescription of training to enhance performance. We assessed the time sustained in swimming, rowing, running and cycling at an intensity eliciting VO2max and determined the specific oxygen uptake (VO2) kinetics and total energy expenditure (Etot-tlim).
METHODS: Four sub-groups of 10 swimmers, 10 rowers, 10 runners and 10 cyclists performed: (i) an incremental protocol to assess the velocity (vVO2max) or power (wVO2max) associated with VO2max and (ii) a square wave transition exercise from rest to vVO2max/wVO2max to assess the time to voluntary exhaustion (Tlim-100%VO2max). The VO2 was measured using a telemetric portable gas analyser (K4b, Cosmed, Rome, Italy) and VO2 kinetics analysed using a double exponential curve fit. Etot-tlim was computed as the sum of its three components: aerobic (Aer), anaerobic lactic (Analac) and anaerobic alactic (Anaalac) contributions.
RESULTS: No differences were evident in Tlim-100%VO2max between exercise modes (swimming 187 ± 25, rowing 199 ± 52, running 245 ± 46 and cycling 227 ± 48 s; mean ± SD). In contrast, the VO2 kinetics profile exhibited a slower response in swimming (21 ± 3 s) compared with the other three modes of exercise (rowing 12 ± 3, running 10 ± 3 and cycling 16 ± 4 s) (P<0.001). Etot-tlim was similar between exercise modes even if the Analac contribution was smaller in swimming compared with the other sports (P<0.001).
CONCLUSION: Although there were different VO2 kinetics and ventilatory patterns, the Tlim-100%VO2max was similar between exercise modes most likely related to the common central and peripheral level of fitness in our athletes
Kinematic and Electromyographic Changes During 200 m Front Crawl at Race Pace
Get PDFThe purpose of this study was to analyse eventual kinematic and electromyographic changes during a maximal 200 m front crawl at race pace. 10 male international level swimmers performed a 200 m maximal front crawl test. Images were recorded by 2 above and 4 under water cameras, and electromyographic signals (EMG) of 7 upper and lower limbs muscles were analysed for 1 stroke cycle in each 50 m lap. Capillary blood lactate concentrations were collected before and after the test. The variables of interest were: swimming speed, stroke length, stroke and kick frequency, hand angular velocity, upper limb and foot displacement, elbow angle, shoulder and roll angle, duration of stroke phases, and EMG for each muscle in each stroke phase. Generally, the kinematic parameters decreased, and a relative duration increased for the entry and pull phases and decreased for the recovery phase. Muscle activation of flexor carpi radialis, biceps brachii, triceps brachii, peitoral major and upper trapezius increased during specific stroke phases over the test. Blood lactate concentration increased significantly after the test. These findings suggest the occurrence of fatigue, characterised by changes in kinematic parameters and selective changes in upper limbs muscle activation according to muscle action.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Experimenting with various styles to optimize the performance per crawl event
No full textIn this study, one disabled world record holder in crawl sprint is taken as a test case. In trying out various styles to optimize his performance, a rotating arm action style appeared to be the fastest on 50m sprint and a glide stroke with high elbow on longer distances. Movement analyses of the swimmer and observation of colored water, displaced by the arm pull, were combined. During the downward movement of the hand in the stroke with high elbow, propulsion could be generated. In the two fastest styles, water appeared to be better displaced backward than in the other styles.status: Publishe
“How Was the Match?”: Semantic similarity between electronic media commentary and work domain analysis key phrases
Get PDFFootball player’s performance can be measured in an objective way (e. g. Goals scored, assists, interceptions), this being seldom a method to compare and rank the best players by categories. Over years of study, many other factors that can influence the players performance were discovered and studied, considering not only objective factors, but also subjective factors. Match commentary from different sources (e.g., social and formal media) also plays an important role on a more subjective performance assessment.
By using semantic similarity analysis, this study aims to contribute to the understanding of the concepts that are used in this commentaries, notably to each extend key phrases associated to match processes are used in commentaries published in social and formal media.info:eu-repo/semantics/acceptedVersio
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