SciCombinator

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Concept: Swimming

185

This paper reviews unsteady flow conditions in human swimming and identifies the limitations and future potential of the current methods of analysing unsteady flow. The capability of computational fluid dynamics (CFD) has been extended from approaches assuming steady-state conditions to consideration of unsteady/transient conditions associated with the body motion of a swimmer. However, to predict hydrodynamic forces and the swimmer’s potential speeds accurately, more robust and efficient numerical methods are necessary, coupled with validation procedures, requiring detailed experimental data reflecting local flow. Experimental data obtained by particle image velocimetry (PIV) in this area are limited, because at present observations are restricted to a two-dimensional 1.0 m(2) area, though this could be improved if the output range of the associated laser sheet increased. Simulations of human swimming are expected to improve competitive swimming, and our review has identified two important advances relating to understanding the flow conditions affecting performance in front crawl swimming: one is a mechanism for generating unsteady fluid forces, and the other is a theory relating to increased speed and efficiency.

Concepts: Fluid dynamics, Fluid mechanics, Computational fluid dynamics, Navier–Stokes equations, Swimming, Goggles, Front crawl

166

Evolutionary constraints which limit the forces produced during bell contractions of medusae affect the overall medusan morphospace such that jet propulsion is limited to only small medusae. Cubomedusae, which often possess large prolate bells and are thought to swim via jet propulsion, appear to violate the theoretical constraints which determine the medusan morphospace. To examine propulsion by cubomedusae, we quantified size related changes in wake dynamics, bell shape, swimming and turning kinematics of two species of cubomedusae, Chironex fleckeri and Chiropsella bronzie. During growth, these cubomedusae transitioned from using jet propulsion at smaller sizes to a rowing-jetting hybrid mode of propulsion at larger sizes. Simple modifications in the flexibility and kinematics of their velarium appeared to be sufficient to alter their propulsive mode. Turning occurs during both bell contraction and expansion and is achieved by generating asymmetric vortex structures during both stages of the swimming cycle. Swimming characteristics were considered in conjunction with the unique foraging strategy used by cubomedusae.

Concepts: Dynamics, Cnidaria, Limited, Swimming, Jet engine, Box jellyfish, Cubozoa, Propulsive efficiency

141

The assessment of body hydration is a complex process, and no measurement is valid for all situations. Bioelectrical impedance vector analysis (BIVA) has emerged as a relatively novel technique for assessing hydration status in sports. We applied BIVA a) to determine hydration changes evoked by an intense synchronized swimming (SS) training session; b) to characterize the sample of young elite swimmers in relation with a nonathletic reference population; and c) to generate its 50%, 75% and 95% percentiles of the bioelectrical variables.

Concepts: Measurement, Psychometrics, Hilbert space, 2000s music groups, Complex number, 1990s music groups, Swimming, Synchronized swimming

45

For more than 70 years unusual sauropod trackways have played a pivotal role in debates about the swimming ability of sauropods. Most claims that sauropods could swim have been based on manus-only or manus-dominated trackways. However none of these incomplete trackways has been entirely convincing, and most have proved to be taphonomic artifacts, either undertracks or the result of differential depth of penetration of manus and pes tracks, but otherwise showed the typical pattern of normal walking trackways. Here we report an assemblage of unusual sauropod tracks from the Lower Cretaceous Hekou Group of Gansu Province, northern China, characterized by the preservation of only the pes claw traces, that we interpret as having been left by walking, not buoyant or swimming, individuals. They are interpreted as the result of animals moving on a soft mud-silt substrate, projecting their claws deeply to register their traces on an underlying sand layer where they gained more grip during progression. Other sauropod walking trackways on the same surface with both pes and manus traces preserved, were probably left earlier on relatively firm substrates that predated the deposition of soft mud and silt . Presently, there is no convincing evidence of swimming sauropods from their trackways, which is not to say that sauropods did not swim at all.

Concepts: Yellow River, Evidence, Swimming, Preservation, Sauropoda, Dinosaur, Claw, Gansu

29

Strong physical activities are often associated with large lung volumes and relatively reduced flow, which may represent a physiological variant but also an obstructive abnormality. Competitive swimmers have also spirometric values even larger than other athletes, although they are at increased risk for asthma or airway hyperresponsiveness.

Concepts: Asthma, Lung, Heart, Mucus, Lung volumes, Bronchus, Swimming, Spirometer

28

Abstract This study investigated the acute effects of different sizes of paddles on the force-time curve during tethered swimming and swimming velocity in front-crawl stroke. Fourteen male swimmers (20.0 ± 3.7 years; 100-m best time: 53.70 ± 0.87 s) performed two 10-s maximal efforts in tethered swimming to obtain peak force, average force, impulse, rate of force development, stroke duration and time to peak force. Swimming velocity, stroke rate and stroke length were obtained from two 25-m maximal swims. Both tests were repeated in five conditions: free swimming, wearing small (280 cm (2) ), medium (352 cm (2) ), large (462 cm (2) ) and extra-large (552 cm (2) ) hand paddles. Compared to free swimming, paddles provided significant increases of peak force (medium: 11.5%, large: 16.7%, extra-large: 21.7%), impulse (medium: 15.2%, large: 22.4%, extra-large: 30.9%), average force (medium: 5.1%, large: 7.5%), rate of force development (extra-large: 11.3%), stroke duration (medium: 9.3%, large: 11.8%, extra-large: 18.5%), time to peak force (medium: 11.1%, large: 15.9%, extra-large: 22.1%), swimming velocity (medium: 2.2%, large: 3.2%, extra-large: 3.7%) and stroke length (medium: 9.0%, large: 9.0%, extra-large: 14.8%), while stroke rate decreased (medium: -6.2%, large: -5.5%, extra-large: -9.5%). It is concluded that medium, large and extra-large paddles influence the force-time curve and change swimming velocity, suggesting these sizes may be useful for force development in water.

Concepts: Time, Acute accent, Swimming, Human swimming

27

The aim of our study was to quantify the effects of a 12-week isolated core training programme on 50-m front crawl swim time and measures of core musculature functionally relevant to swimming.

Concepts: Swimming

27

During competition, high-performance swimmers are subject to repeated physical demands that affect their final performance. Measurement of lactate concentration in blood seeks to indirectly gauge physiologic responses to the increase in physical exercise. Swimmers face multiple maximal-exertion events during competition. Strenuous physical exercise leads to fatigue and, thus, a decrease in sports performance.

Concepts: Psychology, Physical exercise, Test method, Exercise physiology, Swimming, Exercise intolerance, Knitting, Passive voice

27

The aim of the study is to compare the heart rate (HR) and rate of perceived exertion (RPE) responses as internal load indicators while performing duet routines during training and competition, both in the technical and free programs of synchronized swimming (SS). Participants were ten SS Olympic medalists (age: 17.4 ± 3.0 years, height: 164.0 ± 6.1 cm, body mass: 52.0 ± 6.4 kg, training: 36.3 ± 6.2 h·week, experience: 9.2 ± 2.6 years). They were monitored while performing the same technical duet (TD) or free duet (FD), during a training session (T) and during an official competition ©. HR was continuously monitored. RPE was assessed using the Borg CR10 scale. HR responses during T and C were almost identical: pre-exercise mean HR (beats·min) was 130.5 ± 13.9 (T) and 133.6 ± 7.7 ©, and quickly increased yielding mean peak values of 184.8 ± 5.8 (T) and 184.8 ± 6.6 ©, with interspersed bradycardic events down to 86.6 ± 4 (T) and 86.3 ± 5 ©. Routines were perceived as “hard” to “extremely hard” by the swimmers in both conditions, and mean RPE scores (0-10+) were equally high during C (7.9 ± 1.2) and T (7.5 ± 1.2) (P=0.223). RPE inversely correlated with minimum (R=-0.545; P=0.008) and mean HR(R=-0.452; P=0.026), and positively correlated with HR range (R=0.520; P=0.011). The internal load imposed by SS duets performed during training is virtually identical to that elicited in a real competitive situation. Therefore, practicing competitive routines is suitable for developing and maintaining the cardiovascular fitness that is needed for specific conditioning in elite synchronized swimmers, with the added value of favoring exercise automaticity, inter-individual coordination, and artistic expression simultaneously.

Concepts: Value added, Performing arts, Swimming, Olympic sports, Lists of Olympic medalists, Borg, Synchronized swimming, Can You Duet

27

This study aimed to determine whether: i) tethe-red-swimming can be used to identify the asymmetry during front crawl swimming style; ii) swimmers that perform unilateral breathing present greater asymmetry in comparison to others that use bilateral breathing; iii) swimmers of best performance present smaller asymmetry than their counterparts; iv) repeated front crawl swimming movements influence body asymmetry. 18 swimmers were assessed for propulsive force parameters (peak force, mean force, impulse and rate of force development) during a maximal front crawl tethered-swimming test lasting 2 min. A factorial analysis showed that propulsive forces decreased at the beginning, intermediate and end of the test (p<0.05), but the asymmetries were not changed at different instants of the test. When breathing preference (uni- or bilateral) was analyzed, asymmetry remained unchanged in all force parameters (p>0.05). When performance was considered (below or above mean group time), a larger asymmetry was found in the sub-group of lower performance in comparison to those of best performance (p<0.05). Therefore, the asymmetries of the propulsive forces can be detected using tethered-swimming. The propulsive forces decreased during the test but asymmetries did not change under testing conditions. Although breathing preference did not influence asymmetry, swimmers with best performance were less asymmetric than their counterparts.

Concepts: Time, Statistics, Force, Performance, Classical mechanics, Swimming, Asymmetry, Front crawl