Repeatable techniques for assessing changes in passive swimming resistance

Webb, A.; Taunton, D.J.; Hudson, Dominic A.; Forrester, Alexander I. J.; Turnock, S.R.

doi:10.1177/1754337114562875

Cited by 7 publications

(7 citation statements)

References 18 publications

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“…In general, quantification of a (human) swimmer's drag is not straightforward. The value of C D may depend on the body's orientation with respect to the current and on whether the propulsive parts of the swimmer's body (legs and arms) are considered (Webb et al 2011(Webb et al , 2015. Estimation of C D further requires knowledge of the characteristic area A, often taken as the swimmer's wetted surface area, which is not trivial to quantify (see e.g.…”

Section: Swimmer-related Parametersmentioning

confidence: 99%

On the swimming strategies to escape a rip current: a mathematical approach

Withers

Maldonado

2021

Nat Hazards

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Rip currents represent significant hazards to swimmers all around the world. The danger arises when a misinformed swimmer uses an inadequate strategy to escape the rip, such as fighting the current directly. This can lead to fatigue, panic, and in some cases drowning. There exists a range of strategies put forward by experts (both lifeguards and scientists) to escape rip currents. However, these recommendations are based on a limited number of scientific studies and there is still much discrepancy surrounding the best strategy to escape a rip. Thus, here we present a simple, physics-based theoretical model aimed at assessing different escape strategies in terms of their associated ‘energetic cost’ (in work and power) for any given rip current and swimmer’s proficiency level. Many combinations of swimmers and rips are considered, including both idealised and a realistic rip current. Our quantitative results back the common knowledge that swimming against the rip (which is strongly discouraged by lifeguards) is almost universally the worst possible strategy, especially when compared against strategies favoured by experts, such as floating with the current before attempting to swim back to the shore. For a realistic rip, our results suggest that swimming directly against the rip can require several times more power from the swimmer than other strategies advised by lifeguards, thus lending further scientific support to experts’ recommendations. This study may help promote education around the dangers posed by rip currents and how best to address them.

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Section: Swimmer-related Parametersmentioning

confidence: 99%

On the swimming strategies to escape a rip current: a mathematical approach

Withers

Maldonado

2021

Nat Hazards

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“…Experimental video and data capture is able to record the athlete's motion, as well as measure their speed. 35,36 Using these data as inputs, the remaining parameters in equations ( 6) and ( 7) can be estimated and hence h P found.…”

Section: Flykick Propulsive Efficiencymentioning

confidence: 99%

Propulsive efficiency of alternative underwater flykick techniques for swimmers

Phillips

Forrester

Hudson

et al. 2020

Proceedings of the Institution of Mechanical Engineers, Part P:

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Analysis of video and speed data is used to evaluate the efficiency of human underwater flykick. The authors show that by coupling Lighthill’s theory of fish locomotion with human musculoskeletal modelling, it is possible to evaluate the effectiveness of the mechanical and hydrodynamic propulsive components of human underwater flykick. This allows the effect of subtle variances in technique to be assessed by measurement of athlete motion alone. This is demonstrated in an experimental case study of an elite athlete performing two different techniques; one more knee-based or thunniform, and the second more undulatory or carangiform/anguilliform. In finding the mean kinematics of each technique, it is first shown that maintaining stroke-by-stroke consistency of technique leads to an increase in propulsive efficiency. It is further demonstrated that in changing technique, an athlete may swim at the same kick rate but have different propulsive efficiency. This demonstrates the need to determine the energy cost in order to evaluate differing techniques. For the sprint athlete in this case study, it was shown to be more effective to swim with a thunniform technique when at higher velocities and a more anguilliform at lower velocities.

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“…These methods have been used to assess performance of bicycles [1][2][3][4][5] and wheelchairs 6,7 and can be potentially applied to every sport involving rolling or even sliding on a surface, after proper adaptation of the model. Similar approaches based on deceleration measurement have been applied also to swimming, 8 ice skating 9 and bobsleighing. 10 At the industrial level, the automotive industries make a wide use of such kinds of tests [11][12][13][14] that are also defined by Society of Automotive Engineers (SAE) Recommended Practices 15,16 and combined with laboratory and wind tunnel results.…”

Section: Introductionmentioning

confidence: 99%

Proposal of a coast-down model including speed-dependent coefficients for the retarding forces

Baldissera

2016

Proceedings of the Institution of Mechanical Engineers, Part P:

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Coast-down techniques are widely used on bicycles and motorized vehicles in order to estimate retarding forces and respective coefficients. The mathematical model behind coast-down data analysis is usually based on the assumption that both drag and rolling-resistance coefficients do not depend on the vehicle speed. This assumption restricts the model validity to the specifically tested range of speeds and provide averaged values for the force coefficients. In the attempt to overcome this limitation, the proposal of a complete polynomial equation of motion is developed, evaluated and discussed through a human-powered vehicle case study. The analysis points out that the extended model is adequate for experimental data fitting and could potentially provide a more reliable power-speed prediction outside the testing range. However, the expressions included in the model in order to account for speed-dependent coefficients is a first approximation with limited capability to represent these complex phenomena. As a consequence, further experimental testing is needed in order to achieve a validation. Advantages and side effects of both the classical and the complete polynomial models are discussed, concluding that the two approaches could be complementary and could answer different needs that specifically depend on the purpose of the coast-down analysis.

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Repeatable techniques for assessing changes in passive swimming resistance

Cited by 7 publications

References 18 publications

On the swimming strategies to escape a rip current: a mathematical approach

On the swimming strategies to escape a rip current: a mathematical approach

Propulsive efficiency of alternative underwater flykick techniques for swimmers

Proposal of a coast-down model including speed-dependent coefficients for the retarding forces

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