1,721,001 research outputs found
Wearable inertial sensors in swimming kinematics: intra-cyclic analysis of stroke, breath, and kick timing during front-crawl
No full textEffect of swimmer’s head position on passive drag
No full textThe aim of this study was to investigate the effect of the head position on passive drag with a towing-line experiment in a swimming pool. The tests were performed on ten male swimmers with regional level swimming skills and at least 10 years of competitive swimming experience. They were towed underwater (at a depth of 60 cm) at three speeds (1.5, 1.7 and 1.9 m/s) and in two body positions (arms above the swimmer's head and arms alongside the body). These two body positions were repeated while the swimmer's head was positioned in three different ways: head-up, head-middle and head-down in relation to the body's horizontal alignment. The results showed a reduction of 4-5.2% in the average passive drag at all speeds when the head was down or aligned to the swimmer's arms alongside the body, in comparison to the head-up position. A major significant decrease of 10.4-10.9% (p < 0.05) was shown when the head was down or aligned at the swimmer's arms above the swimmer's head. The passive drag tended to decrease significantly by a mean of 17.6% (p < 0.001) for all speeds examined with the arms alongside the body position rather than with the arms above the head position. The swimmer's head location may play an important role in reducing hydrodynamic resistance during passive underwater gliding. © by Matteo Cortesi 2016
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
SYMMETRY OF PROPULSION EXERTED DURING TETHERED- AND FREE-SWIMMING
No full textINTRODUCTION
Swimming is characterized by body propulsion, where the upper limbs play the role of the
main contributor (Zamparo et al., 2020). Recently, the study of the propelling forces involved
during the swimming action has been ecologically allowed using wearable pressure sensors.
Thus, this study analyzed the propelling forces of the two hands during free (Free) and tethered
(Tet) swimming conditions by means of wearable pressure sensors.
METHODS
Eleven regional-level swimmers (age 15.4±0.5y.; body mass 58.0±7.1Kg; stature 168.4±5.0
cm) performed a 10-sec maximal full-tethered test and a 10-sec free-swimming test at front-
crawl only-arms. Two pressure sensors (SEAL, Platysens) were attached to each swimmer’s
hand (dorsal and palmar side) to estimate the propelling forces as the horizontal component of
the product of differential pressure and hand surface. Propelling forces of each hand in terms
of average (FMEAN), impulse (I), peak (FPEAK) and instantaneous (by means of Statistical
Parametric Mapping, SPM) values were analysed as a function of swimming condition and
dominant/non-dominant hand. Furthermore, the symmetry index (SI) of propelling forces was
analysed as a function of swimming condition.
RESULTS
Larger FMEAN, FPEAK, and I were found during Tet compared to Free condition (F>14.29,
p<0.001). SPM highlighted larger FMEAN in Tet condition only at the beginning of the stroke
(from 7 to 28% of stroke cycle duration). Additionally, no significant differences were observed
for FMEAN and FPEAK between the hands (p>.05). SPM and SI confirm non-significant differences
between dominant and non-dominant hands in propelling forces (p>0.05), while larger I was
found in the dominant hand (F=11.11, p<.05).
DISCUSSION
The swimmer appears to exert larger hand propulsion in tethered- than free- swimming. Our
experiments reveal a similar symmetry and hands propelling models in the two analysed
swimming conditions (Tet and Free) despite the fact that the effect of hand kinematic was not
taken into account
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
Influences of Sex on Muscle Architecture and Performance in Elite Field Hockey Players
Full text linkThe aim of this study was to compare muscle architecture and performance between male and female elite Field Hockey players and to investigate the relationships between echo intensity and performance. Twenty-one male (24.3 ± 3.6 y; 75.1 ± 8.5 kg; 176.8 ± 6.4 cm) and nineteen female players (27.4 ± 3.9 y; 61.2 ± 7.4 kg; 164.4 ± 4.9 cm) were tested for muscle thickness (MT) and echo intensity (EI) of trapezius (Trap) and vastus lateralis (VL) muscles. Participants were also assessed for bench press power, and 30 m sprint. Results showed a higher VLMT and TrapMT in male players compared to female players (+22.1%; p = 0.004 and +25.8%; p = 0.001 for VLMT and TrapMT, respectively). A lower VLEI was detected in male players compared to female players (−20.7%; p = 0.001), while no significant differences were detected for TrapEI. Male players were faster than female players in a 30 m sprint and more powerful at the bench press (p < 0.001). Significant correlations were detected between VLEI and 30 m sprint (r = 0.74) in female players only. Results indicate that differences exist between male and female elite Field Hockey players in the EI of lower body muscles, while these differences are not present in the upper body muscles. EI, together with other sprint and power assessments, may represent an important parameter for elite Field Hockey players
Swimmer Hand Trajectory Using Wearable Inertial Magnetic Measurement Units: A Preliminary Study
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