1,720,966 research outputs found
EFFECTS OF AUTONOMIC TONE ON SHORT VERSUS LONG DISTANCE PERFORMANCES IN SWIMMERS
No full textWhatever the swimming specialty, swim training programs generally consist of high volume, which may shifts the heart rate (HR) autonomic control towards vagal predominance. Although it is accepted that an enhanced parasympathetic tone may improve performance on long distances, it is poorly known whether it may affect performance on short distances. PURPOSE. To evaluate resting autonomic tone and swimming performance on short and long distances in highly trained swimmers. METHODS. Two groups of national–level swimmers (all males, crawl specialists) were evaluated: short (S: 50-100 m; n=13; 24±3 yrs) and long (L: 1500 m; n=9; age 19±1 yrs) distance specialists. All swimmers belonged to the same team and were similar for training level. Beat-by-beat HR was recorded at rest in the morning, in supine position, by a HR monitor for 15 minutes. HR variability indexes were calculated from time (RMSSD, pNN50, indexes of vagal tone) and frequency (LF, Low Frequency and HF, High Frequency as absolute values and in normalized units (nu); LF/HF ratio, index of sympathovagal balance) domains. The anaerobic threshold was evaluated by an incremental swimming test with lactate measurements. RESULTS. The percentage of swimmers who showed resting bradycardia tended to be higher in L (78%) than in S (54%) group. HRV indexes did not significantly differ between groups: RMSSD 67±23 vs 66±11 ms, pNN50 40±17 vs 48±10%, LFnu 62.3±12.3 vs 54.4±14.8, HFnu 37.6±12.3 vs 45.6±14.8, LF/HF 2.1±1.9 vs 1.5±1.0 (S vs L group, respectively). In S group, 50 m best time correlated positively (p<0.05) with RMSSD (r=0.64), pNN50 (r=0.73) and absolute HF power (r=0.64), and negatively with LFnu (r=-0.56), but not with anaerobic threshold. On the contrary, in L group 1500 m did not correlate with RMSSD, pNN50 and absolute HF power (although negative trends were perceived), negatively correlated with absolute LF power (r=-0.65 p=0.05), positively correlated to LFnu (r=0.72, p=0.02), and tended to increase with anaerobic threshold. CONCLUSION. L swimmers were not more hypervagotonic than S swimmers, and such adaptation tended to be positively associated with anaerobic threshold. Conversely, high vagal tone appeared somehow detrimental on short swimming performance, as it negatively predicts performance on 50 m events, whereas anaerobic threshold did not
Costumi da gara e prestazioni : valutazioni con un software sperimentale
No full textTra le varie componenti che condizionano la performance natatoria, oltre alle variabili dipendenti dal nuotatore stesso, un fattore estremamente rilevante e che ha consentito negli ultimi anni l'abbattimento di parecchi record è rappresentato dal costume di gara. Abbandonati i tessuti ottenuti dalla lavorazione dei polimeri per decisioni FINA, i produttori hanno dovuto realizzare nuovi costumi. Dopo alcune considerazioni sulle componenti della performance natatoria, si è voluto sperimentare sul campo un nuovo software procedendo al confronto di alcuni nuovi costumi in nuotatori di alto livello
Analysis and comparison by gender of lactate production in young breastroke swimmers
No full textINTRODUCTION The aim of this study was to assess the differences by gender of lactate production in the 200 m breaststroke swimming, at the anaerobic threshold. Mader’s test, proposed on 1976 and modified in distance from its original version, is used to calculate the anaerobic threshold from the lactate production after a second 200 m breaststroke, in a swimming battery test. This is very useful to assess the proper swimming speed in the seasonal training planning. METHODS Twelve male (age 17.3 ± 0.2 years; height 181.2 ± 4.7 m; weight 73.2 ± 2.9 kg; best time on 200 m breaststroke 131.25 s) and female national-level swimmers (age 16.0 ± 0.2 years; height 166,4 ± 3.3 m; weight 54.2 ± 2.6 kg; best time on 200m breaststroke 143.56 s) participated in the study. Tests were performed in a 25 m swimming pool. Each swimmer twice swam a 200 m breaststroke trial: the first at 2 to 3 mmol/L (17 to 20 s slower than the personal record); the second, 30 minutes after the first, at the maximum speed. Blood lactate was measured (Lactate Pro Analyzer) three minutes after the end of each trial. Paired Student’s t test was applied to compare male and female performances and lactate production at the anaerobic threshold between. RESULTS At the anaerobic threshold, male swimmers swam the 200 m breaststroke in 145.72 ± 2.76 s, while females swimmers performed 159.12 ± 3.38 s (p < 0.01). The male swimmers’ lactate production at the anaerobic threshold was 11.0 ± 1.59 mmol/L, whereas female swimmers produced 9.3 ± 1.91 mmol/L (p < 0.05). DISCUSSION Males better performed the 200 m breaststroke swimming at the anaerobic threshold than females.. This can be easily explained by the difference in power between genders. With regard to the lactate production, female swimmers exhibited significantly lower values than males, probably due to the lower ratio between muscle mass and blood volume and to lower glycolytic activity of the skeletal muscles associated with a higher oxidative capacity of the lactate. High aerobic capacity is important for a good 200 m performance; in fact there is a high correlation between the speed corresponding to 4 mmol/L lactate production and the speed of swimmers during the 200 m race. REFERENCES Heck H, Mader A, Hess G, Mücke S, Müller R, Hollmann W. Justification of the 4-mmol/L lactate threshold. (1985) Int J Sports Med. 6(3):117-30. Janssen P. (2001). Lactate threshold training. Running, Cycling, Multisport, Rowing, X-Country Skiing. Human Kinetics, Champaign IL. Olbrecht J, Madsen O, Mader A, Liesen H, Hollmann W. (1985) Relationship between swimming velocity and lactic concentration during continuous and intermittent training exercises. Int J Sports Med. 6(2):74-7. Telford R.D., Hahn A.G., Catchpole E.A., Parker A.R., Sweetenham W.M. (1988) Postcompetition blood lactate concentration in highly ranked Australian swimmers .In: Swimming V, Ungerechts Ed., Human Kinetics, Champaign IL, 277-283
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
The assembly of Ni2+-actin: Some peculiarities
No full textNickel alters the organisation of highly dynamic cytoskeletal elements. In cultured cells Ni2+ causes microtubule aggregation and bundling as well as microfilament aggregation and redistribution. Here, we have analysed the effect(s) of Ni2+ on in vitro actin polymerisation. Using limited proteolysis by trypsin we have suggested that the regions around Arg-62 and Lys-68 change their conformation following Ni2+ binding to the single high-affinity site for divalent cations in the G-actin molecule. We have found that Ni2+ shortens the lag phase of actin polymerisation and increases the rate of assembly mainly because of an increased elongation rate. Ni2+ has no significant effect on the final plateau of actin polymerisation nor on the actin critical concentration. Electron microscopy revealed that actin filaments polymerised by 2 mM Ni2+ showed some tendency to lateral aggregation, being frequently formed by the cohesion of two or three filaments. Furthermore, they often appeared shorter than those of control as also confirmed by the larger amount of free filament ends as well as the faster depolymerisation rate than control
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
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