Swimming Stroke Research Articles

Contribution of limbs’ actions to the four competitive swimming strokes: a nonlinear approach

ABSTRACTThe aim of our study was to assess the effect of the limbs’ actions on the nonlinear properties of the four competitive swimming strokes. Forty-nine swimmers performed all-out sprints at front-crawl, backstroke, breaststroke and butterfly, each one at full stroke (FS), only the arms’ stroke (AS), and only leg kicking (LK), in a total of 12 bouts, 6 per day. A speedo-meter cable was attached to the swimmer’s hip, to collect the speed-time raw data (f = 50Hz). Velocity, speed fluctuation, sample entropy and fractal dimension were derived from the speed-time series. Significant and moderate-strong effects were noted for both stroke and condition in all variables in the study (p ≤ 0.001; 0,560<η2 < 0,952). The four competitive strokes and their three conditions exhibited nonlinear properties. The swimming pattern was less complex and more predictable for LK in comparison to AS and FS. Breaststroke and butterfly have more complex but more predictable patterns than backstroke and front-crawl.

Reconfigurable paramagnetic microswimmers: Brownian motion affects non-reciprocal actuation.

Swimming at low Reynolds number is typically dominated by a large viscous drag, therefore microscale swimmers require non-reciprocal body deformation to generate locomotion. Purcell described a simple mechanical swimmer at the microscale consisting of three rigid components connected together with two hinges. Here we present a simple microswimmer consisting of two rigid paramagnetic particles with different sizes. When placed in an eccentric magnetic field, this simple microswimmer exhibits non-reciprocal body motion and its swimming locomotion can be directed in a controllable manner. Additional components can be added to create a multibody microswimmer, whereby the particles act cooperatively and translate in a given direction. For some multibody swimmers, the stochastic thermal forces fragment the arm, which therefore modifies the swimming strokes and changes the locomotive speed. This work offers insight into directing the motion of active systems with novel time-varying magnetic fields. It also reveals that Brownian motion not only affects the locomotion of reciprocal swimmers that are subject to the Scallop theorem, but also affects that of non-reciprocal swimmers.

Transient Relative Age Effects across annual age groups in National level Australian Swimming

ObjectivesTo determine the prevalence, magnitude and transient patterning of Relative Age Effects (RAEs) according to sex and stroke event across all age-groups at the Australian National age swimming Championships. DesignRepeated years of cross-sectional participation data were examined. MethodsParticipants were 6014 unique male (3185) and female (2829) swimmers (aged 12–18 years) who participated in Freestyle (50, 400m) and/or Breaststroke (100, 200m) at the National age swimming Championships between 2000–2014 (inclusive). RAE prevalence, magnitude and transience were determined using Chi-square tests and Cramer’s V estimates for effect size. Odds Ratios (OR) and 95% Confidence Intervals (CI) examined relative age quartile discrepancies. These steps were applied across age-groups and according to sex and each stroke event. ResultsConsistent RAEs with large-medium effect sizes were evident for males at 12–15 years of age respectively, and with large-medium effects for females at 12–14 respectively across all four swimming strokes. RAE magnitude then consistently reduced with age across strokes (e.g., Q1 vs. Q4 OR range 16year old males=0.94–1.20; females=0.68–1.41). With few exceptions, by 15–16 years RAEs had typically dissipated; and by 17–18 years, descriptive and significant inverse RAEs emerged, reflecting overrepresentation of relatively younger swimmers. ConclusionsPerformance advantages associated with relative age (and thereby likely growth and maturation) are transient. Greater consideration of transient performance and participation in athlete development systems is necessary. This may include revising the emphasis of sport programmes according to developmental stages and delaying forms of athlete selection to improve validity.

Does water temperature influence the performance of key survival skills?

Aquatic survival skills may be compromised in cold water thereby increasing the likelihood of drowning. This study compared physiological, psychological, and behavioral responses of humans treading water and swimming in cold and temperate water. Thirty-eight participants were classified as inexperienced (n=9), recreational (n=15), or skilled (n=10) swimmers. They performed 3 tasks: treading water (120seconds), swim at "comfortable" pace, and swim at "fast" pace in 2 water conditions (28°C vs 10°C). Heart rate, oxygen uptake, psychometric variables, spatio-temporal (swim speed, stroke rate, and stroke length), and coordination type were examined as a function of expertise. Tasks performed in cold water-generated higher cardiorespiratory responses (HR=145±16 vs 127±21bpm) and were perceived about 2 points more strenuous on the Borg scale on average (RPE=14.9±2.8 vs 13.0±2.0). The voluntary durations of both treading water (60±32 vs 91±33seconds) and swimming at a comfortable pace (66±22 vs 103±34seconds) were significantly reduced in cold water. However, no systematic changes in movement pattern type could be determined in either the treading water task or the swimming tasks. Water temperature influences the physical demands of these aquatic skills but not necessarily the behavior. Training treading water and swimming skills in temperate water seems to transfer to cold water, but we recommend training these skills in a range of water conditions to help adapt to the initial "cold-shock" response.

Decentralized control of rhythmic activities in fully-actuated/under-actuated robots

Rhythmic activities such as swimming stroke in the human body are learnable through conscious trainings. Inspiringly, the main objective of this study is to develop a control framework to reproduce the described functionality in the imitating robots. To do so, a two layer supervisory controller is proposed. The high-level controller, which acts as the conscious controller during trainings, is a supervisory dynamic-based controller and uses all system sensory data to generate stable rhythmic movements. On the other hand, the low-level controller in this structure is a distributed trajectory-based controller network. Each node in this network is an oscillatory dynamical system which has the ability to learn and reproduce the desired trajectory. Also, each node has a critic agent which evaluates the control eligibility of the low-level controllers for controlling the system. Then, based on the evaluation, these agents decide to assign the control of the system to the high-level controller or the low-level controllers. By using this structure, the system controller will act as simple and computing efficient as trajectory-based controllers and will perform as stably and robustly as dynamic-based controllers. At last, the applicability of this framework is demonstrated on a fully actuated robot and on an under-actuated biped robot.

The influence of explosive power on the performance of an elite swimmer in 25 and 50 metre pools

Each swimming stroke, and each distance, requires a different approach to strength training. For sprinters in swimming the most essential part is explosive power. The goal of this case study was to find out how explosive training can influence the performance in both long course and short course meters swimming pools. This study was conducted with the cooperation of an elite swimmer over a time period of 6 years. Tests were performed twice a year (June and November) during the years of 2010–2016. The Myotest device was used to measure countermovement jump height. Swimming performance was evaluated by FINA points in the swimmer’s three main disciplines. ANOVA, Cohen’s d and regression equation were used for statistical analysis. The results showed that explosive power does not influence performance in the 50m swimming pool (p = 0.25; r2 = 0.08). However the performance in the 25m pool is directly linked to the level of explosive power of the lower limbs (p < 0.001; r2 = 0.85). The results of the swimmer in the 25m pool are closely related to the level of explosive power of the lower limbs. Performance in the 50m pool might not be affected by level of lower limb power.

Kick, Stroke and Swim: Complement Your Swimming Program by Engaging the Whole Body on Dry Land and in the Pool

The Kick, Stroke and Swim (KSS) program can be used to engage students in swimming-skill acquisition and fitness training using a variety of modalities, strategies and techniques on dry land. Practicing swim strokes and techniques on land gives all levels of swimmers — from beginner to competitive — a kinesthetic awareness of the individual components of each stroke that will enhance skill development and refinement. The KSS program assists with assessing the fundamental techniques of each skill component, may be used with peer assessments, and is a helpful tool to demonstrate proper technique for parental assistance. The swimming strokes executed on a variety of equipment such as a physioball, playground ball, therapy roller, therapy half-roller and BOSU ball, can address the skills of swimmers at different levels. Practicing these skills and techniques on the pool deck and in other land-based spaces during physical education class or at home, may assist students with retention and skill development. In addition, KSS training may enhance stroke acquisition and improvement of a student's overall fitness level, and land training could offer students an opportunity to build a confident skill base before entering the pool. This article will provide techniques, strategies and ideas for physical educators and swim instructors to engage swimmers at all levels.

Copepods encounter rates from a model of escape jump behaviour in turbulence

A key ecological parameter for planktonic copepods studies is their interspecies encounter rate which is driven by their behaviour and is strongly influenced by turbulence of the surrounding environment. A distinctive feature of copepods motility is their ability to perform quick displacements, often dubbed jumps, by means of powerful swimming strokes. Such a reaction has been associated to an escape behaviour from flow disturbances due to predators or other external dangers. In the present study, the encounter rate of copepods in a developed turbulent flow with intensity comparable to the one found in copepods' habitat is numerically investigated. This is done by means of a Lagrangian copepod (LC) model that mimics the jump escape reaction behaviour from localised high-shear rate fluctuations in the turbulent flows. Our analysis shows that the encounter rate for copepods of typical perception radius of ~ {\eta}, where {\eta} is the dissipative scale of turbulence, can be increased by a factor up to ~ 100 compared to the one experienced by passively transported fluid tracers. Furthermore, we address the effect of introducing in the LC model a minimal waiting time between consecutive jumps. It is shown that any encounter-rate enhancement is lost if such time goes beyond the dissipative time-scale of turbulence, {\tau}_{\eta}. Because typically in the ocean {\eta} ~ 0.001m and {\tau}_{\eta} ~ 1s, this provides stringent constraints on the turbulent-driven enhancement of encounter-rate due to a purely mechanical induced escape reaction.

Movement evaluation of front crawl swimming: Technical skill versus aesthetic quality.

The study aim was to compare expert with non-expert swimmers’ rating of the aesthetic and technical qualities of front crawl in video-taped recordings of swimmers with low, middle, and high level proficiency. The results suggest that: i) observers’ experience affects their judgment: only the expert observers correctly rated the swimmers’ proficiency level; ii) evaluation of movement (technical and aesthetic scores) is correlated with the level of skill as expressed in the kinematics of the observed action (swimming speed, stroke frequency, and stroke length); iii) expert and non-expert observers use different strategies to rate the aesthetic and technical qualities of movement: equating the technical skill with the aesthetic quality is a general rule non-expert observers follow in the evaluation of human movement.

Comparing Acoustic Tag Attachments Designed for Mobile Tracking of Hatchling Sea Turtles

The poorly understood movements of sea turtles during the ‘lost years’ of their early life history have been characterized as a ‘passive drifter’ stage. Biologging technology allows us to study patterns of dispersal, but the small body size of young life stages requires particular consideration that such tagging does not significantly impede animal movements. We tested the effect of instrument attachment methods for mobile acoustic tracking of hatchling sea turtles, including a design that would be suitable for leatherback turtles (Dermochelys coriacea). We obtained 8-week-old hatchery-reared green sea turtles (Chelonia mydas) (n = 12 individuals) and examined the effect of attaching Vemco V5 acoustic tags. Each animal’s swim speed, swimming depth, and stroke frequency were determined under three scenarios: control, direct Velcro® attachment to the carapace, and harness attachment, to determine if there was a significant difference amongst treatments. Turtle swimming speed was significantly slower during the middle period of the trial for the harness attachment compared with the control. No significant change in swim speed was observed when the tag was attached directly with Velcro®, and no significant change in dive depth was observed for either treatment compared to the control. Stroke frequency was significantly greater compared to the control at the end of the trial for the Velcro® attachment only, although there was no corresponding increase in swimming speed. This information can be used to design effective approaches for actively tracking free-ranging hatchling sea turtles to understand dispersal and survival of these vulnerable marine species.

Highly Efficient Freestyle Magnetic Nanoswimmer.

The unique swimming strategies of natural microorganisms have inspired recent development of magnetic micro/nanorobots powered by artificial helical or flexible flagella. However, as artificial nanoswimmers with unique geometries are being developed, it is critical to explore new potential modes for kinetic optimization. For example, the freestyle stroke is the most efficient of the competitive swimming strokes for humans. Here we report a new type of magnetic nanorobot, a symmetric multilinked two-arm nanoswimmer, capable of efficient "freestyle" swimming at low Reynolds numbers. Excellent agreement between the experimental observations and theoretical predictions indicates that the powerful "freestyle" propulsion of the two-arm nanorobot is attributed to synchronized oscillatory deformations of the nanorobot under the combined action of magnetic field and viscous forces. It is demonstrated for the first time that the nonplanar propulsion gait due to the cooperative "freestyle" stroke of the two magnetic arms can be powered by a plane oscillatory magnetic field. These two-arm nanorobots are capable of a powerful propulsion up to 12 body lengths per second, along with on-demand speed regulation and remote navigation. Furthermore, the nonplanar propulsion gait powered by the consecutive swinging of the achiral magnetic arms is more efficient than that of common chiral nanohelical swimmers. This new swimming mechanism and its attractive performance opens new possibilities in designing remotely actuated nanorobots for biomedical operation at the nanoscale.

What is the best swimming stroke to master for beginners in water safety tests?

The aim of this study was to ascertain whether performance in a series of water safety tests, in clothed and swimsuit conditions, were dependent on the swim stroke that beginners selected for traversing maximal distance. A total of 45 children (9.6 ± 1.6 years) involved in a learning programme were asked to complete six tests to: travel their maximal distance in water; hold a vertical position; float on their back for as long as possible; perform a maximal number of rotations from front to back in 10 seconds; complete their deepest immersion dive; and perform a final integrated test composed of the previous tasks that were successfully executed in isolation. Pupils were divided into three groups according to the swim stroke they had selected for the first test. The results revealed that the breaststroke group was less affected by wearing clothes in performance on the maximal distance and the final integration test, and was able to tread water for a longer period of time. The backstroke group maintained a horizontal position on their backs for a longer period of time, and was able to rotate position more frequently from front to back. No effect of preferred swim stroke was noted in the maximal immersion dive test. Overall, the front crawl group was most affected by wearing clothes when traversing a maximal distance, floating on their back and performing the final integrated test. Findings suggested that breaststroke and backstroke may be more important to teach beginners for performance in water safety tests.

Socioeconomics Influences on the Water Competencies of Young Adult Polish Males

Abstract Despite the popularity of aquatic recreation and its well-promoted prophylactic and therapeutic values, not a lot is known about how socio-cultural background influences the acquisition of water competency. The aim of this study was to assess the influence of socio-economic and environmental factors on the swimming and rescue skills of male university students (n = 521) aged 19-20 years residing in the Region of Warmia and Mazury, Poland. An anonymous questionnaire was used as a diagnostic tool to elicit information on participants’ social backgrounds (such as parental income and level of education). Participants provided self-estimates of swimming and rescue competency that included non-stop distance swimming, familiarity with selected swimming strokes, and their estimated rescue ability. The results suggest that students’ self-estimated swimming competency, the distance they could swim non-stop, and the capacity to swim various strokes increased in association with higher levels of educational background of the father, higher levels of monthly income, and increased size of residential agglomeration. The level of rescue skills also improved with increases in the educational background of both parents, the size of residential agglomeration, and the monthly budget. No significant differences were found in rescue competency levels when analyzed by the mothers’ educational experience. Levels of both swimming and rescue competencies were lower than those reported in comparable studies. Socio-economic status (such as a lack of discretionary time and income for families with a lower socio-economic status) and place of residence (such as lack of facilities in small villages and towns) mediated the opportunity to acquire water competencies or gain experience with aquatic activity. Methods for addressing socio-economic barriers to the acquisition of swimming and rescue competency are discussed and recommendations for further research are made.

Setting the pace of microswimmers: when increasing viscosity speeds up self-propulsion

It has long been known that some microswimmers seem to swim counter-intuitively faster when the viscosity of the surrounding fluid is increased, whereas others slow down. This conflicting dependence of the swimming velocity on the viscosity is poorly understood theoretically. Here we explain that any mechanical microswimmer with an elastic degree of freedom in a simple Newtonian fluid can exhibit both kinds of response to an increase in the fluid viscosity for different viscosity ranges, if the driving is weak. The velocity response is controlled by a single parameter Γ, the ratio of the relaxation time of the elastic component of the swimmer in the viscous fluid and the swimming stroke period. This defines two velocity–viscosity regimes, which we characterize using the bead-spring microswimmer model and analyzing the different forces acting on the parts of this swimmer. The analytical calculations are supported by lattice-Boltzmann simulations, which accurately reproduce the two velocity regimes for the predicted values of Γ.

Factors Predictive of Human One‐Kilometer Ice Swimming Race Time Performance

Ice swimming is a popular sport under consideration as a possible Winter Olympic Event. Swimming in water that is ≤5°C brings inherent risks such as hypothermia and factors that influence swimming performance are poorly understood in this regard. This study evaluated International Ice Swimming Association data for one‐kilometer ice swimming performance that included swimmer age, sex (144 male; 75 female), height/weight for body mass index (BMI) calculation, swim time, swim stroke, and swim conditions for 177 swimmers who (without wetsuits) performed 219 different ice swimming races on 9 different times and locations (December 19, 2015–August 10, 2016). Swimmers using the crawl stroke required 19.38 ± 0.27 minutes for these one‐kilometer swims. Four factors were highly predictive of swim time. Age is most predictive, air temperature and gender are moderately predictive, and BMI is least predictive. As age increases, swim time gets significantly slower. Warmer air temperature was surprisingly associated with slower swim time. Males were faster than females. In many sports decreased BMI is predictive of improved fitness, however increased BMI is also associated with improved thermal conservation, a factor that could be important for ice swimming. A BMI of 20 was the absolute lower observed limit for ability to complete these one‐kilometer swims, increasing BMI was associated with increases in race time, and gender specific BMI differences were not statistically significant. When swimmers completed more than one race, the second swim was significantly faster than the first. Water temperature did not significantly impact swim times. The physiology of cold‐water exposure can be applied to athletes, survival situations, the military, and the medical field. This study provides data that increases the understanding of the human body's physiological reaction when exposed to cold conditions, specifically in water, and provides a framework that allows for the prediction of ice water swim times.

SHOULDER INJURIES IN SWIMMING: REASONS

Swimming is one of the most popular recreational and competitive sporting activities. The repetitive nature of the swimming stroke and demanding training programs of its athletes raises a number of concerns regarding incidence and severity of injuries that a swimmer might experience during a competitive season. A number of risk factors have previously been identified but the level of evidence from individual studies, as well as the level of certainty that these factors predispose a swimmer to pain and injury. We have examined 134 leading swimmers, among them 50 female and 84 male aged between 11 and 18 years having trained from 1 to 9 years. In order to clarify the implementation of young swimmers shoulders areas state Latvian swimmers questioner‘s connected to shoulder area pain summarizing was used. We figure out, that in all swimmers groups is evidence tendency- pain in shoulders area appears when swimming in small or big paddles, using swimming resistance and in fast interval training. From all four swimmer groups –Most’’ successful’’ group is 11-12 years old swimmers. From 25 respondents in this age group answer about feeling pain often -1 swimmers, when swimming fly and one –when swimming freestyle. But when swimming with paddles – more complaints, when swimming in big paddles-8 answers and in small paddles-6 answers. The largest number -9 answers about pain, when swimming long distances using one stroke. The total number of positive answers is dominated by the age group 13-14 years. The greatest manifestation of painful sensations when swimming in the shoulder blades, with intense swimming and when using swimming resistances equipment. A similar trend is observed in the group of 15-16 year old. However, the number of complaints is less than in the group of 13-14 year old. On pain during swimming in the shoulder blades, 15 and 20 swimmers complain, respectively. In the older group, 17-18 years- the least number of complaints, although swimming in big paddles often causes pain.

Swimming and diving energetics in dolphins: a stroke-by-stroke analysis for predicting the cost of flight responses in wild odontocetes

Exponential increases in hydrodynamic drag and physical exertion occur when swimmers move quickly through water, and underlie the preference for relatively slow routine speeds by marine mammals regardless of body size. Because of this and the need to balance limited oxygen stores when submerged, flight (escape) responses may be especially challenging for this group. To examine this, we used open-flow respirometry to measure the energetic cost of producing a swimming stroke during different levels of exercise in bottlenose dolphins (Tursiops truncatus). These data were then used to model the energetic cost of high-speed escape responses by other odontocetes ranging in mass from 42 to 2738 kg. The total cost per stroke during routine swimming by dolphins, 3.31±0.20 J kg-1stroke-1, was doubled during maximal aerobic performance. A comparative analysis of locomotor costs (LC; in Jkg-1stroke-1), representing the cost of moving the flukes, revealed that LC during routine swimming increased with body mass (M) for odontocetes according to LC=1.46±0.0005M; a separate relationship described LC during high-speed stroking. Using these relationships, we found that continuous stroking coupled with reduced glide time in response to oceanic noise resulted in a 30.5% increase in metabolic rate in the beaked whale, a deep-diving odontocete considered especially sensitive to disturbance. By integrating energetics with swimming behavior and dive characteristics, this study demonstrates the physiological consequences of oceanic noise on diving mammals, and provides a powerful tool for predicting the biological significance of escape responses by cetaceans facing anthropogenic disturbances.

Traction reveals mechanisms of wall effects for microswimmers near boundaries.

The influence of a plane boundary on low-Reynolds-number swimmers has frequently been studied using image systems for flow singularities. However, the boundary effect can also be expressed using a boundary integral representation over the traction on the boundary. We show that examining the traction pattern on the boundary caused by a swimmer can yield physical insights into determining when far-field multipole models are accurate. We investigate the swimming velocities and the traction of a three-sphere swimmer initially placed parallel to an infinite planar wall. In the far field, the instantaneous effect of the wall on the swimmer is well approximated by that of a multipole expansion consisting of a force dipole and a force quadrupole. On the other hand, the swimmer close to the wall must be described by a system of singularities reflecting its internal structure. We show that these limits and the transition between them can be independently identified by examining the traction pattern on the wall, either using a quantitative correlation coefficient or by visual inspection. Last, we find that for nonconstant propulsion, correlations between swimming stroke motions and internal positions are important and not captured by time-averaged traction on the wall, indicating that care must be taken when applying multipole expansions to study boundary effects in cases of nonconstant propulsion.

Evaluation of the Finis Swimsense® and the Garmin Swim™ activity monitors for swimming performance and stroke kinematics analysis.

AimsThe study aims were to evaluate the validity of two commercially available swimming activity monitors for quantifying temporal and kinematic swimming variables.MethodsTen national level swimmers (5 male, 5 female; 15.3±1.3years; 164.8±12.9cm; 62.4±11.1kg; 425±66 FINA points) completed a set protocol comprising 1,500m of swimming involving all four competitive swimming strokes. Swimmers wore the Finis Swimsense and the Garmin Swim activity monitors throughout. The devices automatically identified stroke type, swim distance, lap time, stroke count, stroke rate, stroke length and average speed. Video recordings were also obtained and used as a criterion measure to evaluate performance.ResultsA significant positive correlation was found between the monitors and video for the identification of each of the four swim strokes (Garmin: X2 (3) = 31.292, p<0.05; Finis:X2 (3) = 33.004, p<0.05). No significant differences were found for swim distance measurements. Swimming laps performed in the middle of a swimming interval showed no significant difference from the criterion (Garmin: bias -0.065, 95% confidence intervals -3.828–6.920; Finis bias -0.02, 95% confidence intervals -3.095–3.142). However laps performed at the beginning and end of an interval were not as accurately timed. Additionally, a statistical difference was found for stroke count measurements in all but two occasions (p<0.05). These differences affect the accuracy of stroke rate, stroke length and average speed scores reported by the monitors, as all of these are derived from lap times and stroke counts.ConclusionsBoth monitors were found to operate with a relatively similar performance level and appear suited for recreational use. However, issues with feature detection accuracy may be related to individual variances in stroke technique. It is reasonable to expect that this level of error would increase when the devices are used by recreational swimmers rather than elite swimmers. Further development to improve accuracy of feature detection algorithms, specifically for lap time and stroke count, would also increase their suitability within competitive settings.

Lattice Boltzmann simulations of the bead-spring microswimmer with a responsive stroke—from an individual to swarms

Propulsion at low Reynolds numbers is often studied by defining artificial microswimmers which exhibit a particular stroke. The disadvantage of such an approach is that the stroke does not adjust to the environment, in particular the fluid flow, which can diminish the effect of hydrodynamic interactions. To overcome this limitation, we simulate a microswimmer consisting of three beads connected by springs and dampers, using the self-developed waLBerla and framework based on the lattice Boltzmann method and the discrete element method. In our approach, the swimming stroke of a swimmer emerges as a balance of the drag, the driving and the elastic internal forces. We validate the simulations by comparing the obtained swimming velocity to the velocity found analytically using a perturbative method where the bead oscillations are taken to be small. Including higher-order terms in the hydrodynamic interactions between the beads improves the agreement to the simulations in parts of the parameter space. Encouraged by the agreement between the theory and the simulations and aided by the massively parallel capabilities of the waLBerla- framework, we simulate more than ten thousand such swimmers together, thus presenting the first fully resolved simulations of large swarms with active responsive components.