Swimming Power Research Articles

Flow features induced by a rod-shaped microswimmer and its swimming efficiency: A two-dimensional numerical study

Abstract The swimming performance of rod-shaped microswimmers in a channel was numerically investigated using the two-dimensional lattice Boltzmann method (LBM). We considered variable-length squirmer rods, assembled from circular squirmer models with self-propulsion mechanisms, and analyzed the effects of the Reynolds number (Re), aspect ratio (ε), squirmer-type factor (β) and blockage ratio (κ) on swimming efficiency (η) and power expenditure (P). The results show no significant difference in power expenditure between pushers (microswimmers propelled from the tail) and pullers (microswimmers propelled from the head) at the low Reynolds numbers adopted in this study. However, the swimming efficiency of pushers surpasses that of pullers. Moreover, as the degree of channel blockage increases (i.e., κ increases), the squirmer rod consumes more energy while swimming, and its swimming efficiency also increases, which is clearly reflected when ε ≤ 3. Notably, squirmer rods with a larger aspect ratio ε and a β value approaching 0 can achieve high swimming efficiency with lower power expenditure. The advantages of self-propelled microswimmers are manifested when ε > 4 and β = ±1, where the squirmer rod consumes less energy than a passive rod driven by an external field. These findings underscore the potential for designing more efficient microswimmers by carefully considering the interactions between the microswimmer geometry, propulsion mechanism and fluid dynamic environment.

Intermittent swimming and muscle power output in brook trout, Salvelinus fontinalis.

Slow and sustainable intermittent swimming has recently been described in several Centrarchid fishes, such as bluegill and largemouth bass. This swimming behavior involves short periods of body-caudal fin undulation alternating with variable periods of coasting. This aerobic muscle powered swimming appears to reduce energetic costs for slow, sustainable swimming, with fish employing a "fixed-gear" or constant tailbeat frequency and modulating swimming speed by altering the length of the coasting period. We asked if this swimming behavior was found in other fish species by examining volitional swimming by brook trout in a static swimming tank. Further, we employed muscle mechanics experiments to explore how intermittent swimming affects muscle power output in comparison to steady swimming behavior. Brook trout regularly employ an intermittent swimming form when allowed to swim volitionally, and consistently showed a tailbeat frequency of ~2 Hz. Coasting duration had a significant, inverse relationship to swimming speed. Across a range of slow, sustainable swimming speeds, tailbeat frequency increased modestly with speed. The duration of periods of coasting decreased significantly with increasing speed. Workloop experiments suggest that intermittent swimming reduces fatigue, allowing fish to maintain high power output for longer compared to continuous activity. This study expands the list of species that employ intermittent swimming, suggesting this behavior is a general feature of fishes.

Physical performance determinants in competitive youth swimmers: a systematic review.

Youth swimming performance is determined by several physiological, biomechanical and anthropometric characteristics. This review aimed to identify physical performance determinants of youth swimming performance, assessing strength, power, anaerobic, aerobic and body composition measures. ̇ METHODS: Searches were conducted in electronic databases (PubMed and Web of Science) using keywords relating to swimming and physiological measures, supplemented by citation searching of similar reviews. A total of 843 studies were identified in the initial search. The following inclusion criteria were used: participants were competitive/trained swimmers; swimming time-trial or event was conducted; data was provided on one or more physiological parameters; study was published in English and peer-reviewed. A total of 43 studies met the inclusion criteria. Risk of bias was assessed using Joanna Briggs Institute (JBI) checklist. Cross-sectional studies scored between 4-8 and randomised-controlled trials scored 8-9 on their respective JBI checklists. Youth swimming performance was determined by muscle strength, muscle power, lean body mass, anaerobic and aerobic metabolism measures in most studies, where improved performance values of these variables were conducive to swimming performance. Body fat percentage did not have a clear relationship in youth swimmingperformance. Findings of this review suggest that greater levels of muscle strength, muscle power and lean body mass are favourable in swimming performance, with muscle strength and muscle power particularly beneficial for start and turn performance. Anaerobic and aerobic metabolism measures were good determinants of swimming performance, with middle- and long-distance events more influenced by the latter. Body fat percentage has a nuanced relationship with swimming performance, where further investigation is required. Findings were inconsistent across studies, potentially due to unidentified confounding factors. • Greater muscular strength and power qualities, anaerobic and aerobic capacities, and lean body mass are conducive to swimming performance. • Body fat percentage has a nuanced relationship with swimming performance. • Practitioners should consider general strength and power training as a useful tool to enhance performance in their youth competitors.

Optimal swimming locomotion of snake-like robot in viscous fluids

Snake-like robots have several joints that enable them to swim in various types of viscous fluids such as water, mud, and clay by varying the undulation. Because the optimal swimming motion is assumed to be different in fluids with different viscosities, we constructed an equation of motion for a snake-like robot swimming in viscous fluids and attempted to find the optimal swimming motion via numerical analysis. We constructed a snake-like robot comprising eight links in this study that could swim in four fluids with different kinematic viscosities, and measured their joint positions and relative angles during swimming. Accordingly, we proposed a method for identifying multiple unknown parameters of fluid forces acting on a body using the unscented Kalman filter, which could determine the unknown added mass and drag coefficient. Subsequently, we clarified that the inertial drag model is effective in water (small viscosity, μ∼1mPas), while the friction drag model is effective in oil (large viscosity, μ>100mPas). By considering the increase in frictional drag due to boundary layer thinning in the proposed model, we identified the constant drag coefficient regardless of the swimming frequency. Next, we employed the constructed numerical model to explore the trade-off relationship between consumed power and velocity during swimming using exhaustive search. Consequently, we confirmed that the swimming frequency decreased as the fluid viscosity increased under the same swimming power consumption. Moreover, the wavelength of undulation was confirmed to be between half and one wavelength, regardless of the viscosity.

A systematic investigation into the effect of roughness on self-propelled swimming plates

This study examines the effects of surface topography on the flow and performance of a self-propelled swimming (SPS) body. We consider a thin flat plate with an egg-carton roughness texture undergoing prescribed undulatory swimming kinematics at Strouhal number $0.3$ and tail amplitude to length ratio $0.1$ ; we use plate Reynolds numbers $Re=6$ , 12 and $24\times 10^3$ , and focus on $12\,000$ . As the roughness wavelength is decreased, we find that the undulation wave speed must be increased to overcome the additional drag from the roughness and maintain SPS. Correspondingly, the extra wave speed raises the power required to maintain SPS, making the swimmer less efficient. To decouple the roughness and the kinematics, we compare the rough plates to equivalent smooth cases by matching the kinematic conditions. We find that all but the longest roughness wavelengths reduce the required swimming power and the unsteady amplitude of the forces when compared to a smooth plate undergoing identical kinematics. Additionally, roughness can enhance flow enstrophy by up to 116 % compared to the smooth cases without a corresponding spike in forces; this suggests that the increased mixing is not due to increased vorticity production at the wall. Instead, the enstrophy is found to peak strongly when the roughness wavelength is approximately twice the boundary layer thickness over the $Re$ range, indicating the roughness induces large-scale secondary flow structures that extend to the edge of the boundary layer. This study reveals the nonlinear interaction between roughness and kinematics beyond a simple increase or decrease in drag, illustrating that roughness studies on static shapes do not transfer directly to unsteady swimmers.

Muscle power production during intermittent swimming in bluegill sunfish.

Locomotion is essential for the survival and fitness of animals. Fishes have evolved a variety of mechanisms to minimize the cost of transport. For instance, bluegill sunfish have recently been shown to employ intermittent swimming in nature and in laboratory conditions. We focused on the functional properties of the power-producing muscles that generate propulsive forces in bluegill to understand the implications of intermittent activity. We used in vivo aerobic or red muscle activity parameters (e.g., oscillation frequency and onset time and duration of activation) in muscle physiology experiments to examine muscle power output during intermittent versus steady swimming in these fish. Intermittent propulsion involves swimming at relatively slow speeds with short propulsive bursts alternating with gliding episodes. The propulsive bursts are at higher oscillation frequencies than would be predicted for a given average swimming speed with constant propulsion. The work-loop muscle physiology experiments with red muscle demonstrated that intermittent activity allows muscle to produce sufficient power for swimming compared with imposed steady swimming conditions. Further, the intermittent muscle activity in vitro reduces fatigue relative to steady or continuous activity. This work supports the fixed-gear hypothesis that suggests that there are preferred oscillation frequencies that optimize efficiency in muscle use and minimize cost of transport.

Analysis of fish migration in correspondence with wood and rock-made instream structures

Anthropic exploitation of soil, forests, and water bodies contributes to the modification of river flow regimes and sediment transport dynamics, thus affecting fish habitats and water quality. In the last decades, the increasing awareness of the consequences of such modifications on natural contexts has stimulated researchers and practitioners to provide more innovative solutions aiming at enhancing river biodiversity. Recently developed eco-friendly approaches for river restoration evidenced the necessity of more careful planning and management of natural resources, including the maintenance and enhancement of fish species' habitats. The present study aims at assessing the interaction of different types of wood- and rock-made instream structures with river flow regimes and habitat requirements of many freshwater fish species, accounting for the influence of downstream scour potholes to facilitate fish species migration and spawning. Experimental tests showed that instream structures cause deep scour holes characterized by low flow velocity zones, thus decreasing the required fish swimming power and potentially providing suitable conditions for the migration of freshwater fish species. Using dimensional analysis, empirical relationships were derived to optimize the longitudinal distance between subsequent instream structures, accounting for the effects of various structure geometries and fish biological characteristics. Nevertheless, further investigation is needed to validate the proposed relationships at prototype scale. This study ultimately contributes at providing tools to design river instream structures favorable to fish migration.

KONTRIBUSI POWER LENGAN DAN POWER TUNGKAI TERHADAP KEMAMPUAN RENANG GAYA BEBAS PADA ATLET GARUDA LAUT MAKASSAR

The population of this study was the Makassar sea eagle swimming athlete. Using purposive-sampling in taking samples and the test instruments used: 1) Medicine Ball Push, 2) vertical jump, 3) stopwatch to measure speed. The variables of this study include power and speed in freestyle swimming. Data analysis techniques using regression and correlation tests with a significance of 95% (α = 0.05). Based on the results of the analysis of the data this study shows that: (1) there is a significant effect of arm power on the ability to swim freestyle in Makassar sea eagle athletes with a contribution of 38.8% (2) there is a significant effect of leg power on the ability to swim freestyle in Makassar sea eagle athletes seen from the contribution of 60.4% (3) there is a significant influence of arm power and leg power together on the ability to swim freestyle in Makassar sea eagle athletes seen from the contribution of 61.4%.

Cost of Transport of Undulating Fin Propulsion.

Autonomous robots are used to inspect, repair and maintain underwater assets. These tasks require energy-efficient robots, including efficient movement to extend available operational time. To examine the suitability of a propulsion system based on undulating fins, we built two robots with one and two fins, respectively, and conducted a parametric study for combinations of frequency, amplitude, wavenumber and fin shapes in free-swimming experiments, measuring steady-state swimming speed, power consumption and cost of transport. The following trends emerged for both robots. Swimming speed was more strongly affected by frequency than amplitude across the examined wavenumbers and fin heights. Power consumption was sensitive to frequency at low wavenumbers, and increasingly sensitive to amplitude at high wavenumbers. This increasing sensitivity of amplitude was more pronounced in tall rather than short fins. Cost of transport showed a complex relation with fin size and kinematics and changed drastically across the mapped parameter space. At equal fin kinematics as the single-finned robot, the double-finned robot swam slightly faster (>10%) with slightly lower power consumption (<20%) and cost of transport (<40%). Overall, the robots perform similarly to finned biological swimmers and other bio-inspired robots, but do not outperform robots with conventional propulsion systems.

Bobbing in the park: wild swimming, conviviality and belonging

ABSTRACT With swimming pools and lidos closed during the pandemic, the number of people dipping their toes in rivers, lakes and seas and swimming wild has swelled. In this paper, we reflect on the ways in which swimmers living in cities have found ways of immersing themselves, and how they have forged new friendships and communities in the water. Drawing on conversations with swimmers at a lake in an urban park and focusing on small and embodied everyday social interactions, from flashes of nudity to recognition between strangers, we explore how the opening – and temporary closures – of the lake have sparked convivial moments and how swimming reconfigures urban public space. Within this paper we engage with ideas of belonging and becoming. We think about absence and exclusion flowing alongside belonging and conviviality, and reflect on what that means for our understandings of leisure spaces, urban publics and bodies. We suggest that the power of wild swimming to restore, refresh and bring people together can revive our ideas about the place of water and wilderness in cities, while also drawing attention to enduring and pervasive inequalities.

What’s at play? Power, transnational coaches and the global hegemony of performance within Danish elite swimming

This paper examines the discourses in power in Danish elite swimming from 2003 to 2013. Gramsci’s perspective was used to deconstruct the hegemonic cultural leadership enacted by coaches and administrators in the Danish Swimming Federation and Team Danmark. Transnational coaches were also engaged in the hegemonic practices towards elite swimmers in Denmark in the quest for Olympic medals. With the exception of a few abortive rebellions, the athletes complied with the hegemonic practices because their coaches and the Danish Swimming Federation were the gatekeepers of their success. These findings are discussed in the context of the evolvement of a neo-liberal funding structure for elite sport in the Western world. The transnational coaches appear to be representing an ideological superstructure in which sporting performance became the sole measure of success (and allocation of funds) in Danish elite sport policy. This study suggests that there is a need of ensuring that athletes’ voices are being heard through an independent regulatory council.

Effects of a 12-Week Detraining Period on Physical Capacity, Power and Speed in Elite Swimmers.

This study aims to evaluate the effects of a prolonged transition period (detraining) on the physical capacity, power, and speed parameters of elite swimmers. Fourteen swimmers (seven females and seven males) aged 20.4 ± 1.7 years participated in the study. The athletes were subjected to two rounds of identical tests at 12-week intervals during the detraining period (DP), which consisted of an evaluation of the athletes’ body weight and composition, a measurement of the power of their lower limbs (Keiser squat, countermovement jump (CMJ), akimbo countermovement jump (ACMJ)) and upper limbs (Keiser arms) on land, and 20-m swimming using the legs only (Crawl Legs test), arms only (Crawl Arms test), and full stroke (Front Crawl test). An analysis of variance revealed a significant effect of the main factor, Gender, on all the measured parameters, while for the factor Detraining, except for Front Crawl (W) (F = 4.27, p = 0.061), no significant interaction effect (Gender × Detraining) was revealed. Among both the male and the female participants, a reduction in lactate-threshold swimming speed (LT Dmax) and a reduction in swimming speed and power on the Crawl Arms, Crawl Legs, and Front Crawl tests was observed after 12 weeks. There were also statistically significant reductions in ACMJ and CMJ jump height and upper-limb power (Keiser squat) among the female and male swimmers. There were no significant changes in body weight or body composition. The study showed a clear deterioration in results for most of the parameters, both for those measured on land and for those measured in water.

Does the Athletes’ Leg Muscle Power Increase After the Tabata Aquatic Program?

The study purpose. This study aims to evaluate the effect of the Tabata aquatic training method program in increasing the muscle power of beginner level athletes.&#x0D; Materials and methods. The researcher used a mixed method in this study. There were twenty swimming athletes (n = 20, age: 14.40 ± 1.18 years, height: 169.20 ± 3.18 cm, weight: 62.20 ± 2.26 kg) who agreed to participate in this study and were divided into two groups. The treatment group (n = 10) received the Tabata aquatic program and the control group (n = 10) swam every day without participating in any physical activity. The Tabata aquatic program was carried out for 9 weeks with a frequency of 3 times a week. After implementing the Tabata aquatic program, 10 athletes were interviewed. This study applied a quantitative research instrument, including squat jumps, and a qualitative research instrument, including individual in-depth interviews lasting for 30 minutes each. Analysis of quantitative data using IBM SPSS version 25.0 and qualitative data using thematic analysis was applied.&#x0D; Results. Quantitative study results showed that there was a significant increase in the squat jumps test (leg muscle power) in the treatment group and vice versa, there was no increase in the control group. However, in qualitative research results, most participants mentioned that the Tabata aquatic program is a fun training method and has a positive effect. &#x0D; Conclusions. After carrying out the Tabata aquatic program for 9 weeks, we confirmed that this training method has a great impact on improving athletes’ leg muscle power in swimming.

Peculiarities of respiratory functions in qualified swimmers exposed to multidirectional physical loads

The peculiarities of the swimmers’ respiratory system response to a special physical load were studied. The swimmers of high sports qualification aged 16–18 years old, who specialize in swimming at distances of various lengths, underwent the examination. At the first stage, we used exercises aimed at enhancing the anaerobic work power in swimming. At the second stage, the parameters of the swimmers’ respiratory system response to the load in aerobic and anaerobic zone were studied. At the third stage of the study, the changes of the swimmers’ respiratory functions under physical loads at the level of MOC (maximum oxygen consumption) were researched. The investigation of respiratory system functions of stayer swimmers was conducted with the use of a Spirolab-3 spirometer (spirograph). We found that the recovery of qualified swimmers can be activated when aerobic and anaerobic mechanisms of energy metabolism are combined. The results of the study confirm that the swimmers’ respiratory functions influence the processes of recovery of their working capacity after being exposed to multidirectional physical loads. The sprinters’ anaerobic mechanisms of muscle function are better developed. The stayers’ aerobic mechanisms of energy metabolism function better. In order to activate the recovery of qualified swimmers, it is advisable to combine aerobic and anaerobic mechanisms of energy metabolism.

High intensity trainings as a method of developing speed and power in swimming (peer review)

High intensity trainings as a method of developing speed and power in swimming (peer review)

SwimOne. New Device for Determining Instantaneous Power and Propulsive Forces in Swimming.

The propulsive forces and instantaneous power that are generated by a swimmer have a great influence on the swimming performance. This works presents a new device, called SwimOne, for measuring propulsive force and estimating the instantaneous power of the swimmer. In addition, the detailed prototype is able to exert a customizable opposition force to the swimmer for training purpose. The conceptual idea is presented by describing the differential equation of the swimmer and the protocol for a factible estimation of the instantaneous power. The variables that are to be measured and estimated are identified and, consequently, the sensor and actuator systems can be selected. The high-level and detailed designs of the prototype are presented together with the protocol that is carried out in order to validate the sensor and actuation systems. The device is able to monitor the variables of interest of the swimmer together with the propulsive force and instant power. Finally, some experiments are carried out providing the results of several participants swimming in crawl, backstroke, butterfly, and breaststroke styles in the presence of different opposition force. The preliminary results show that SwimOne is valid for measuring instantaneous force and power with different loads in swimming.

Squirming in a viscous fluid enclosed by a Brinkman medium.

Cell motility plays important roles in a range of biological processes, such as reproduction and infections. Studies have hypothesized that the ulcer-causing bacterium Helicobacter pylori invades the gastric mucus layer lining the stomach by locally turning nearby gel into sol, thereby enhancing its locomotion through the biological barrier. In this work, we present a minimal theoretical model to investigate how heterogeneity created by a swimmer affects its own locomotion. As a generic locomotion model, we consider the swimming of a spherical squirmer in a purely viscous fluid pocket (representing the liquified or degelled region) surrounded by a Brinkman porous medium (representing the mucus gel). The use of the squirmer model enables an exact, analytical solution to this hydrodynamic problem. We obtain analytical expressions for the swimming speed, flow field, and power dissipation of the swimmer. Depending on the details of surface velocities and fluid properties, our results reveal the existence of a minimum threshold size of mucus gel that a swimmer needs to liquify in order to gain any enhancement in swimming speed. The threshold size can be as much as approximately 30% of the swimmer size. We contrast these predictions with results from previous models and highlight the significant role played by the details of surface actuations. In addition to their biological implications, these results could also inform the design of artificial microswimmers that can penetrate into biological gels for more effective drug delivery.

Dual function of epaxial musculature for swimming and suction feeding in largemouth bass.

The axial musculature of many fishes generates the power for both swimming and suction feeding. In the case of the epaxial musculature, unilateral activation bends the body laterally for swimming, and bilateral activation bends the body dorsally to elevate the neurocranium for suction feeding. But how does a single muscle group effectively power these two distinct behaviours? Prior electromyographic (EMG) studies have identified fishes' ability to activate dorsal and ventral epaxial regions independently, but no studies have directly compared the intensity and spatial activation patterns between swimming and feeding. We measured EMG activity throughout the epaxial musculature during swimming (turning, sprinting, and fast-starts) and suction feeding (goldfish and pellet strikes) in largemouth bass (Micropterus salmoides). We found that swimming involved obligate activation of ventral epaxial regions whereas suction feeding involved obligate activation of dorsal epaxial regions, suggesting regional specialization of the epaxial musculature. However, during fast-starts and suction feeding on live prey, bass routinely activated the whole epaxial musculature, demonstrating the dual function of this musculature in the highest performance behaviours. Activation intensities in suction feeding were substantially lower than fast-starts which, in conjunction with suboptimal shortening velocities, suggests that bass maximize axial muscle performance during locomotion and underuse it for suction feeding.

Swim-Specific Resistance Training: A Systematic Review.

Muniz-Pardos, B, Gomez-Bruton, A, Matute-Llorente, A, Gonzalez-Aguero, A, Gomez-Cabello, A, Gonzalo-Skok, O, Casajus, JA, and Vicente-Rodriguez, G. Swim-specific resistance training: A systematic review. J Strength Cond Res 33(10): 2875-2881, 2019-The purpose of this systematic review was to determine which type of swim-specific training is most beneficial to enhance swimming performance and to determine which specific strength- or power-related tests better predict swimming performance. A search was conducted on PubMed, Cochrane Plus, and SPORTDiscus up to June 2018. Studies were distributed into 2 main categories: swim-specific dry land resistance training (SDLRT) and specific in-water swimming power training (SSWPT). From 1,844 citations, 25 met the inclusion criteria. It was determined that SSWPT was the most appropriate method to improve swimming performance, with tethered swimming protocols being the most studied and effective. In addition, SDLRT was a competent method to enhance swimming performance, and specifically, the inclusion of inertial training might evoke greater improvements in both strength/power capacities and swimming performance, than traditional resistance training. In conclusion, tether forces showed the greatest associations with swimming performance, although the efficacy of tethered swimming as an SSWPT method is yet to be confirmed. Further research should focus on the effects of SDLRT to verify the greater transfer of dry land resistance practices to swimming performance, with inertial training being potentially more beneficial than traditional resistance training.

Maximal Speed of Underwater Locomotion

Background. An increasing interest in unmanned underwater vehicles continues to draw attention to swimming in aquatic animals. Their high speed continues to surprise researchers. In particular, the high dolphin speed caused a series of attempts to explain its paradox, which continues to this day. Some researchers believe that even rigid bodies, shaped like water animals, provide an attached flow pattern, as opposed to the widespread view of the inevitable separation. The possible explanation may be in the perfect body form, which provides an attached flow pattern (without boundary layer separation). Elongated unseparated shapes can not only reduce the pressure drag but also delay the laminar-to-turbulent transition in the boundary layer, significantly reducing the friction drag. Thus, the highest possible swimming speeds are expected in aquatic animals. Objective. We will try to prove that the low drag and the high speed of aquatic animals can only be ensured by their unseparated shape (as a rigid body), neglecting flexibility and compliance. Methods. We will use: a) shape calculations of special bodies of revolution with negative pressure gradients near the tail similar to fish trunks with the use of the developed before approach; b) the known drag estimations of such shapes for laminar and turbulent cases; c) the swimming power balance and the theory of ideal propeller; d) statistical analysis of available data about the length, the speed and the aspect ratio of aquatic animals. Results. The swimming speed of most aquatic animals is proportional to the length of the body in power 7/9. The exception is whale locomotion that occurs in turbulent mode at supercritical Reynolds numbers. Conclusions. The perfect body shapes of most aquatic animals provide an attached laminar flow pattern. Estimated maximum speeds for laminar and turbulent cases show that the special shaped unseparated hulls can greatly increase the speed of underwater vehicles and SWATH ships. Further increase in speed can be achieved by using supercavitation and greater than animal capacity-efficiency.