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A protocol of intermittent exercise (shuttle runs) to train young basketball players
No full textThe purpose of this study was to set up a protocol of intermittent exercise to train young basketball players. Twenty-one players were asked to complete (a) an incremental test to determine maximal oxygen uptake (VO2max), the speed at the ventilatory threshold (vthr) and the energy cost of "linear" running (Cr) and (b) an intermittent test composed of 10 shuttle runs of 10-second duration and 30-seconds of recovery (total duration: about 6 minutes). The exercise intensity (the running speed, vi) was set at 130% of vthr. During the intermittent tests, oxygen uptake (VO2) and blood lactate concentration (Lab) were measured. The average pretraining VO2 calculated for a single bout (131 ± 9 ml · min(-1) kg(-1)) was about 2.4 times greater than the subjects' measured VO2max (54.7 ± 4.6 ml · min(-1) · kg(-1)). The net energy cost of running (9.2 ± 0.9 J · m(-1) · kg(-1)) was about 2.4 times higher than that measured at constant "linear" speed (3.9 ± 0.3 J · m(-1) · kg(-1)). The intermittent test was repeated after 7 weeks of training: 9 subjects (control group [CG]) maintained their traditional training schedule, whereas for 12 subjects (experimental group [EG]) part of the training was replaced by intermittent exercise (the same shuttle test as described above). After training, the VO2 measured during the intermittent test was significantly reduced (p < 0.05) in both groups (-10.9% in EG and - 4.6 in CG %), whereas Lab decreased significantly only for EG (-31.5%). These data suggest that this training protocol is effective in reducing lactate accumulation in young basketball player
Energetics of shuttle runs: the effects of distance and change of direction.
No full textShuttle runs can be used to study the physiological responses in sports (such as basketball) characterized by sprints (accelerations/decelerations) and changes of direction.
Purpose: To determine the energy cost (C) of shuttle runs with different turning angles and over different distances (with different acceleration/deceleration patterns).
Methods: Nine basketball players were asked to complete 6 intermittent tests over different distances (5, 10, 25 m) and with different changes of direction (180° at 5 and 25 m; 0°, 45°, 90°, and 180° at 10 m) at maximal speed (v ≈ 4.5 m/s), each composed by 10 shuttle runs of 10-s duration and 30-s recovery; during these runs oxygen uptake (VO2), blood lactate (Lab), and C were determined.
Results: For a given shuttle distance (10 m) no major differences where observed in VO2 (~33 mL · min–1 · kg–1), Lab (~3.75 mM), and C (~21.2 J · m–1 · kg–1) when the shuttle runs were performed with different turning angles. For a given turning angle (180°), VO2 and Lab were found to increase with the distance covered (VO2 from 26 to 35 mL · min–1 · kg–1; Lab from 0.7 to 7.6 mM) while C was found to decrease with it (from 29.9 to 10.6 J · m–1 · kg–1); the relationship between C and d (m) is well described by C = 92.99 × d0.656, R2 = .971. Conclusions: The metabolic demands of shuttle tests run at maximal speeds can be estimated based on the running distance, while the turning angle plays a minor role in determining C
Effects of elastic recoil on maximal explosive power of the lower limbs
No full texthe maximal explosive power during a two legs jump was measured on four competitive athletes [mean age 24(SD 4.3) years; height 1.79 (SD 0.09) m; body mass 68.7 (SD 12.8) kg] at different starting knee angles (70, 90, 110, 130 and 150 degrees). The experiments were performed on a newly developed instrument with which both force and speed could be measured using a force platform and a wire tachometer, respectively, and on a conventional force platform. At the smallest knee angle (70 degrees) the mean power output (W in watts per kilogram) developed during the jump was found not to differ significantly between the two methods (P > 0.1). At the larger knee angles W was 18.4% (90 degrees), 34.5% (110 degrees), 47.4% (130 degrees) and 19.4% (150 degrees) higher using the conventional force platform (P < 0.05 throughout). The difference of W between the two methods was attributed to the recovery of elastic energy due to the counter movement which immediately preceded the jump on the conventional platform, but not on the newly developed instrument. Indeed because of a mechanical arrangement which prevented the subject from moving towards the platforms, eccentric work (W-) could not be performed on the newly developed instrument; whereas W- on the conventional force platform was almost negligible at 70 degrees knee angle [mean 1.7 (SD 2.3 J)] reached a maximum of 13.1 (SD 7.9) J at 130 degrees and decreased again to a mean 4.7 (SD 3.6) J for the largest angle (150 degrees). Furthermore, on the conventional force platform, the force at the onset of the positive speed phase (Fi) was an increasing function of W- (r2 = 0.519, P < 0.001); and the difference of W between the conventional and new instruments was larger the larger the difference of Fi (r2 = 0.391, P < 0.01)
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
Effects of elastic recoil on maximal explosive power of the lower limbs. Eur J Appl Physiol Occup Physiol. 1997;75(4):289-97
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