1,720,963 research outputs found
Wearable inertial sensors in swimming kinematics: intra-cyclic analysis of stroke, breath, and kick timing during front-crawl
No full textSYMMETRY 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
RESISTED SWIMMING: COMPARISON BETWEEN THRUST FORCE EXERTED BY THE HAND AND APPLIED TO THE TETHERED DEVICE
No full textPERFORMANCE DESCRIPTORS IN ARTISTIC SWIMMING TECHNIQUE: THE RELATIONSHIP BETWEEN PROPULSION, SYMMETRY,STABILITY, AND HEIGHT IN DIFFERENT STATIC FIGURES
No full text
HAND THRUST DURING FREE AND TETHERED SWIMMING: AN ANALYSIS OF ASYMMETRY
No full textINTRODUCTION: Analyzing athletes’ parameters, such as forces during swimming, is essential to enhance performance (1,2).
The use of wearable sensors could facilitate this process due to their cost-effectiveness, ease of use, and ecological approach.
In this research, we investigated how hand thrust forces vary according to two swimming tests (tethered vs. free) and between the two hands (dominant vs. non-dominant). We hypothesized larger forces in terms of average force (Fmean), impulse (I), and peak force (Fpeak) in tethered compared with the free swimming and in the dominant compared with the non-dominant hand.
METHODS: Eleven skilled swimming athletes (age = 15.4 ± 0.5y.; body mass = 58.0 ± 7.1Kg; stature = 168.4 ± 5.0 cm) performed a 10-second tethered front crawl only arms test (Tet), and 10 seconds free front crawl only arms test (Free) wearing two wearable pressure sensors, one for each hand. The thrust force of each hand was estimated as the product of differential pressure (palmar minus dorsal side) and hand surface. Considering circle-shaped hand kinematics, only the horizontal component of hand thrust force was used for the analysis. Average force (FMEAN), impulse (I), average peak (FPEAK), and instantaneous (by means of Statistical Parametric Mapping, SPM) were analyzed as a function of swimming condition and dominant/non-dominant hand. The symmetry index (SI) was analyzed as a function of swimming conditions.
RESULTS: Results indicated larger Fmean, Fpeak, and I during Tet compared to the Free condition (F > 4.23, p < .05; Fmean: Tet = 34.0 ± 9.7 N vs. Free = 28.7 ± 7.8 N; Fpeak: Tet = 74.6 ± 22.0 N vs. Free = 66.8 ± 15.2 N; I: Tet = 28.0 ± 5.3 Ns vs. Free = 22.0 ± 5.3 Ns). Whereas SI was non-significant. SPM highlighted a larger Fmean in Tet condition only at the beginning of the stroke (entry phase, from 7 to 28% of the cycle).
In addition, non-significant differences were observed for Fmean between the hands (p > .05), and SPM confirmed these results (p > .05). However, larger Fpeak and I in the dominant compared with the non-dominant hand were found (F > 11.11, p < .05; Fpeak: dominant = 65.3 ± 15.9 N vs. non-dominant = 62.7 ± 14.4 N; I: dominant = 26.3 ± 8.0 Ns vs. non- dominant = 23.5 ± 5.6 Ns).
CONCLUSION: The swimmer appears to exert larger hand propulsion in tethered- than free- swimming. However, our findings of the symmetry model and the hand-propelling balance during tethered- and free-swimming were not conclusive, and further investigations could help in better understanding this phenomenon (3).
REFERENCES:
1) Takagi et al., (2021). Sports Biomechanics.
2) Zamparo et al., (2020). European Journal of Applied Physiology 3) Knihs et al., (2022). Strength & Conditioning Journa
Relationship between propulsion, symmetry, stability, and height in three different static figures of artistic swimming
No full text
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
- …
