Drag In Swimming Research Articles

The Load-Velocity Slope Is an Indicator of the Active Drag in all Competitive Swimming Strokes.

Active drag in swimming is a critical variable that affects swimmers' performance as well as the physiological load, but it is challenging for practitioners to assess this variable. This study aimed to assess if the load-velocity profiling method can be used as an indicator of active drag. A total of 419 swimmers performed three semi-tethered swimming trials in their speciality among the four competitive strokes with different external loads. Linear regression between external load and swimming velocity, as well as the external load relative to the body mass and swimming velocity, were established. The active drag and drag coefficient of each swimmer were calculated using a velocity perturbation method. There were significant correlations of the active drag with the absolute slope (r ≥ 0.713, p < 0.001) and relative slope (r ≥ 0.538, p < 0.001) in all four strokes and both sexes. A multiple regression analysis exhibited that the primary determinant of these relationships was the drag coefficient (semi-partial correlation ≥0.404, p < 0.001). The effects of the height and body mass index (BMI) on the relationship between the drag and the absolute slope were small (0.195 ≤ semi-partial correlation ≤0.248, p < 0.001) in both cases, which became either non-significant (height: p ≥ 0.282) or trivial (BMI: -0.099 ≤ semi-partial correlation ≤ -0.073, p ≤ 0.009). These results indicate that the absolute load-velocity slope is a strong indicator of the active drag, and the relative slope is useful when indirectly assessing the drag coefficient.

Estimation of Passive Drag in Swimming via Experimental and Computational Means

Discussed is a comparison of computational and experimental evaluations of passive drag during human swimming. Experimentally, ten trials were conducted per athlete at five chosen velocities, using a commercial resistance trainer to record the tension force in a rope during a streamline position tow test. The resistive force recorded was assumed equal to the passive drag force and an average value of passive drag was found across each tow test. Mean passive drag values measured during the tow test were agreed well with existing experimental data across the range of velocities used, varying between 20 N at 1 ms−1 up to 100 N at 2 ms−1. Computationally, using the immersed boundary method in OpenFOAM, basic geometry validation cases and streamline passive drag cases were simulated. Validation cases were completed on 2D cylinders and 3D spheres with the drag coefficient found at low and high Reynolds numbers, using the simpleFoam solver within OpenFOAM. Results tended to be slightly over predictive when compared with existing simulation and experimental data in literature. The accuracy of results could potentially be improved using a finer mesh and better quality geometries. The passive drag was also computed using OpenFOAM over a range of velocities, similar to the experiments, varying from 30 N at 1 ms−1 to 120 N at 2 ms−1. Drag forces computed using simpleFoam were over predictive when compared to existing literature and the completed experiments, likely due to the inaccuracy of the geometry used in the simulations. When results were compared to existing literature for swimmers not in a perfect streamline position, more similar to the geometry used in this study, results were in better agreement. The accuracy of the results could be improved using a better quality geometry in the correct position.

Using Wearables to Monitor Swimmers’ Propulsive Force to Get Real-Time Feedback and Understand Its Relationship to Swimming Velocity

Evidence on the role of propulsion compared to drag in swimming, based on experimental settings, is still lacking. However, higher levels of propulsion seem to lead to faster swimming velocities. The aim of this study was to understand the variation in a set of kinematic and kinetic variables between two swimming sections and their relationship to swimming velocity. The sample consisted of 15 young adult recreational swimmers (8 males: 20.84 ± 2.03 years; 7 females: 20.13 ± 1.90 years). Maximum swimming velocity and a set of kinematic and kinetic variables were measured during two consecutive sections of the swimming pool. Differences between sections were measured and the determinants of swimming velocity were analyzed. Swimming velocity, propulsive force, and the other kinematic and kinetic variables did not change significantly (p &lt; 0.05) between sections (only the intra-cyclic fluctuation of swimming velocity decreased significantly, p = 0.005). The modeling identified the propulsive force, stroke length, and active drag coefficient as the determinants of swimming velocity. Swimming velocity was determined by the interaction of kinematic and kinetic variables, specifically propulsive force and active drag coefficient.

Body Morphology and Drag in Swimming: CFD Analysis of the Effects of Differences in Male and Female Body Types

This study analyzes the effect of the morphological characteristics of swimmers on passive drag and determines whether the female or male body type is more efficient for gliding. As a result of puberty, males and females develop different body structures; this study investigates whether these changes in shape influence drag. Computational fluid dynamics (CFD) simulations carried out in Ansys Fluent software were used to calculate the drag force and coefficient from 2D models of swimmers in streamline position, generated based on common anthropometric measurements. Both the top and side view profiles of the swimmers were simulated, unique to this study. The normalized male and female body shapes were simulated at different velocities, and it was demonstrated that the male body shape has a lower drag coefficient than the female body shape by 10.1% and 2.8% for top view and side view profiles, respectively. The in-depth analysis and simulation of models with varying hip and chest dimensions found a significant and positive correlation between hip and chest size and drag, with the chest size having the largest effect of an average 12.2% increase in drag per 5% increase in chest breadth. The results from modifying anthropometric variables explain the discrepancy between the drag experienced by male and female swimmers and show that enlarged hips and chests cause an increase in resistance. The differences between drag for males and females were found to be comparable to the 6.2% and 7.7% drag differences between full-body fastskin and normal suits, indicating measurable impact on performance. These findings suggest that the morphology of swimmers does have a significant effect on drag and that the male body shape is more hydrodynamic than the female body shape.

Rheological Properties and Drag Reduction Performance of Puffer Epidermal Mucus.

Most species of fish are covered with mucus, which provides the effect of reduction in swimming drag. In this paper, three concentrations of puffer epidermal mucus were obtained from the epidermal mucosa of puffer. The rheological properties and the drag reduction performance of the puffer epidermal mucus were characterized via a rheometer experimental and numerical simulation method. The relationship between the rheological properties and the drag reduction performance was analyzed and discussed, and the drag reduction mechanism of the puffer epidermal mucus was further explored. The results showed that the best drag reduction rate was 6.2% when the inflow velocity and concentration of puffer epidermal mucus were 0.1 m/s and 18.2 g/L, respectively. The rheological properties of puffer epidermal mucus are viscoelastic, and the mucus forms a sliding surface, which reduces the frictional drag of the fluid. In conclusion, this paper may provide a reference for the development of drag-reducing agents and drag-reducing research studies on other fish mucus.

Development of high performance walking training shoes by using hybrid pneumatic elements

We aimed to develop a new method for evaluating the drag in front-crawl swimming at various velocities and at full stroke. In this study, we introduce the basic principle and apparatus for the new method, which estimates the drag in swimming using measured values of residual thrust (MRT). Furthermore, we applied the MRT to evaluate the active drag (Da) and compared it with the passive drag (Dp) measured for the same swimmers. Da was estimated in five-stages for velocities ranging from 1.0 to 1.4 m s−1; Dp was measured at flow velocities ranging from 0.9 to 1.5 m s−1 at intervals of 0.1 m s−1. The variability in the values of Da at MRT was also investigated for two swimmers. According to the results, Da (Da = 32.3 v3.3, N = 30, R2 = 0.90) was larger than Dp (Dp = 23.5 v2.0, N = 42, R2 = 0.89) and the variability in Da for the two swimmers was 6.5% and 3.0%. MRT can be used to evaluate Da at various velocities and is special in that it can be applied to various swimming styles. Therefore, the evaluation of drag in swimming using MRT is expected to play a role in establishing the fundamental data for swimming.

Assessment of passive drag in swimming by numerical simulation and analytical procedure

ABSTRACTThe aim was to compare the passive drag-gliding underwater by a numerical simulation and an analytical procedure. An Olympic swimmer was scanned by computer tomography and modelled gliding at a 0.75-m depth in the streamlined position. Steady-state computer fluid dynamics (CFD) analyses were performed on Fluent. A set of analytical procedures was selected concurrently. Friction drag (Df), pressure drag (Dpr), total passive drag force (Df+pr) and drag coefficient (CD) were computed between 1.3 and 2.5 m · s−1 by both techniques. Df+pr ranged from 45.44 to 144.06 N with CFD, from 46.03 to 167.06 N with the analytical procedure (differences: from 1.28% to 13.77%). CD ranged between 0.698 and 0.622 by CFD, 0.657 and 0.644 by analytical procedures (differences: 0.40–6.30%). Linear regression models showed a very high association for Df+pr plotted in absolute values (R2 = 0.98) and after log–log transformation (R2 = 0.99). The CD also obtained a very high adjustment for both absolute (R2 = 0.97) and log–log plots (R2 = 0.97). The bias for the Df+pr was 8.37 N and 0.076 N after logarithmic transformation. Df represented between 15.97% and 18.82% of the Df+pr by the CFD, 14.66% and 16.21% by the analytical procedures. Therefore, despite the bias, analytical procedures offer a feasible way of gathering insight on one’s hydrodynamics characteristics.

Developing a methodology for estimating the drag in front-crawl swimming at various velocities

We aimed to develop a new method for evaluating the drag in front-crawl swimming at various velocities and at full stroke. In this study, we introduce the basic principle and apparatus for the new method, which estimates the drag in swimming using measured values of residual thrust (MRT). Furthermore, we applied the MRT to evaluate the active drag (Da) and compared it with the passive drag (Dp) measured for the same swimmers. Da was estimated in five-stages for velocities ranging from 1.0 to 1.4ms−1; Dp was measured at flow velocities ranging from 0.9 to 1.5ms−1 at intervals of 0.1ms−1. The variability in the values of Da at MRT was also investigated for two swimmers. According to the results, Da (Da=32.3 v3.3, N=30, R2=0.90) was larger than Dp (Dp=23.5 v2.0, N=42, R2=0.89) and the variability in Da for the two swimmers was 6.5% and 3.0%. MRT can be used to evaluate Da at various velocities and is special in that it can be applied to various swimming styles. Therefore, the evaluation of drag in swimming using MRT is expected to play a role in establishing the fundamental data for swimming.

Reliability of estimating active drag in swimming using the assisted towing method with fluctuating speed

The reliability of active drag values was examined using a method that compared free swim speed with measurements taken by towing swimmers slightly faster than their maximum swim speed, while allowing their intra-stroke speed fluctuations. Twelve national age and open level swimmers were tested on two alternate days (Day 1 and Day 2). All participants completed four maximum swim speed, three passive drag and five active drag trials on each of the days. The reliability was determined using within-participant intra-class correlation coefficients (ICC) within each day and between the days. The ICCs for Day 1 and Day 2 were 0.82 and 0.85, respectively, while the comparison of the mean active drag values between days was 0.93. The data showed that the assisted towing method (ATM) with fluctuating speed was only moderately reliable within a single test. However, this method was more reliable when using the average value of active drag from both days (ICC = 0.93). This study identified that the ATM method with fluctuating speed had moderate reliability within-participant trials on values in a single day but high reliability for the average active drag values across different days.

The effect of different inter-pad distances on the determination of active drag using the Measuring Active Drag system

The Measuring Active Drag (MAD) system was developed to determine active drag in swimming by measuring the push-off force exerted at fixed pads placed below the waterline. The imposed inter-pad distance, which to date has been kept constant while using the MAD system, could affect the active drag because it requires the use of different stroke frequencies. The aim of the present study was therefore to determine the effect of inter-pad distance on active drag at a given speed. In particular, drag-velocity curves at three different inter-pad distances (1.25m, 1.35m and 1.45m) were determined using the MAD system for eleven competitive swimmers. Variation of 16% in inter-pad distance (14% change in stroke frequency) revealed no significant difference in calculated active drag between different inter-pad distances and a low (<5%) average coefficient of variation over different inter-pad distances was found. In addition, inter-test reliability, which was determined for the two 1.35m conditions only, was high (ICC>0.90) for measurements on two consecutive days. The results suggest that it may not be necessary to adapt the inter-pad distance of the MAD system based on anthropometric characteristics of the subject or the velocity-related stroke length in free swimming.

Comparative Analysis of Active Drag Using the MAD System and an Assisted Towing Method in Front Crawl Swimming

The measurement of active drag in swimming is a biomechanical challenge. This research compared two systems: (i) measuring active drag (MAD) and (ii) assisted towing method (ATM). Nine intermediate-level swimmers (19.7 ± 4.4 years) completed front crawl trials with both systems during one session. The mean (95% confidence interval) active drag for the two systems, at the same maximum speed of 1.68 m/s (1.40-1.87 m/s), was significantly different (p = .002) with a 55% variation in magnitude. The mean active drag was 82.3 N (74.0-90.6 N) for the MAD system and 148.3 N (127.5-169.1 N) for the ATM system. These differences were attributed to variations in swimming style within each measurement system. The inability to measure the early catch phase and kick, along with the fixed length and depth hand place requirement within the MAD system generated a different swimming technique, when compared with the more natural free swimming ATM protocol. A benefit of the MAD system was the measurement of active drag at various speeds. Conversely, the fixed towing speed of the ATM system allowed a natural self-selected arm stroke (plus kick) and the generation of an instantaneous force-time profile.

Prediction of passive and active drag in swimming

In order to understand the physical origin of passive resistance in swimming the resistance breakdown for a swimmer is investigated. A combination of empirical methods and theoretical analysis is used to predict passive resistance in the speed range 0 – 2ms-1 and is shown to provide similar results to those from experimental testing. Typical magnitudes of wave, viscous pressure and skin friction resistance contribute 59%, 33% and 8% of total passive resistance respectively at free swim speed. A comparison is made between the widely used Velocity Perturbation Method and a Naval Architecture based approach in predicting active drag. For the swimmer investigated the two approaches predict active drag of 131.4N and 133.9N for a swimming speed of 1.53ms-1. However, the results predicted from the Velocity Perturbation Method have a much higher uncertainty and the Naval Architecture based approach is suggested as a more robust method of predicting active drag.

Variability in Measurement of Swimming Forces

An analysis was conducted to identify sources of true and error variance in measuring swimming drag force to draw valid conclusions about performance factor effects. Passive drag studies were grouped according to methodological differences: tow line in pool, tow line in flume, and carriage in tow tank. Active drag studies were grouped according to the theoretical basis: added and/or subtracted drag (AAS), added drag with equal power assumption (AAE), and no added drag (ANA). Data from 36 studies were examined using frequency distributions and meta-analytic procedures. It was concluded that two active methods (AAE and ANA) had sources of systematic error and that one active method (AAS) measured an effect that was different from that measured by passive methods. Consistency in drag coefficient (Cd) values across all three passive methods made it possible to determine the effects of performance factors.

A new device for estimating active drag in swimming at maximal velocity

A new device was designed to measure the active drag during maximal velocity swimming based on the assumption of equal useful power output in two cases: with and without a small additional drag. A gliding block was used to provide an adjustable drag, which was attached to the swimmer and measured by a force transducer. Six swimmers of national standard (3 males, 3 females) participated in the test. For the males, the mean active drag ranged from 48.57 to 105.88 N in the front crawl and from 54.14 to 76.37 N in the breaststroke. For the females, the mean active drag ranged from 36.31 to 50.27 N in the front crawl and from 36.25 to 77.01 N in the breaststroke. During testing, the swimmer's natural stroke and kick were not disturbed. We conclude that the device provides a useful method for measuring and studying active drag.

APPROXIMATION OF ACTIVE DRAG FORCES DURING FREESTYLE SWIMMING USING VALUES OF VELOCITY, FORCE, AND POWER

Measuring active drag in swimming is problematic due to the difficulty in assessing force produced in water without affecting the velocity of the swimmer. This problem makes the concurrent measurement of velocity and force production a difficult task and replication of effort in two independent situations may be unreliable (one to measure force and one velocity). Using a large number of subjects of varying ability in a replicable situation of maximum effort for each measurement may be one way to determine the drag velocity relationships. PURPOSE To determine the relationships among the maximum velocity (Vmax), force (Fmax), and power (Pmax) that can be measured during freestyle swimming and to derive the velocity (v) dependence of active drag force (Fd) in freestyle swimming. METHODS 156 swimmers (17 ±2.3 yrs) completed three tests to measure Vmax, Fmax, and Pmax, Vmax was determined using two 13.72 m maximal effort swims. Fmax production was measured during a maximal effort swim with the subject tethered to a computer and force transducer system using a length of elastic tubing. Power was calculated using the product of average velocity and resistance force from a weight and a pulley system over a 10 m maximal effort swim. Pmax was determined by progressively increasing the force of resistance until the measured power peaked and began to decrease. RESULTS Past estimates of active swimming drag have utilized power fits for example Fd=20.72v2.48 (Sanders et al., 2001). Using this type of analysis the relationships of force and power to velocity were Fd=46.66v1.816 (R2=0.70) and P=11.41v3.371 (R2=0.85). However, the data obtained was more closely fit by the exponential functions Fd=14.94e1.237v (R2=0.73) and P=1.452e2.264v (R2=0.87). CONCLUSION vmax, Fmax, and Pmax are highly associated despite being measured independently. Furthermore, these three variables can be used to examine the relationship between drag force and velocity in freestyle swimming. Supported by USA Swimming.

A Hydrodynamic Study of Active Drag in Swimming.

The purpose of this study is to measure active drag, which is dynamic drag acting on a self-propelling swimmer in water. We developed a new measurement device, which was capable of measuring active drag without disturbing natural swimming in a circulating water channel. Four collegiate skilled swimmers volunteered to participate in this study. The subjects were asked to swim front crawl and to keep the pre-determined stroke frequency within a range of 0 m/s to 1.8 m/s flow velocity. The active drag was estimated by means of the relationship between residual thrust (thrust minus the resistance) and passive drag (static drag acting on a prone position swimmer). As a result of these development, it was possible to measure active drag more precisely than before, and to obtain the experimental equation that predicted the active drag within a range of Reynolds number equaled the actual swimming velocity.

A Hydrodynamic Study of Active Drag in Swimming.

The purpose of this study is to measure an active drag in competitive swimming. At first, the active drag of the front crawl is measured by using the original measurement device which is developed for this experiment. The active drag is estimated by means of the relationship between the residual thrust and passive drag. As a result, the experimental equation concerning with the relation between the active drag and Reynolds number was obtained. According to the comparison this study with previous study, good agreement was obtained between the previous results and theoretical prediction.

Evaluation of Active Drag in Swimming Using the Surface and Submerged Hydrodynamic Body Technique 711

A recent technique is employed to assess active drag in elite U.S. swimmers. This technique, described by Kolmogorov and Duplishcheva(1992), requires a swimmer to perform two separate maximal 50 meter sprints while untethered and tethered to a hydrodynamic drag device of known drag. Comparing the mean velocities over 30 meters of free swimming to tethered swimming allows for the computation of active drag (Fad) during the untethered sprint. This device is a metal cylinder filled with water and supported by a carrying board made of penoplast. Video analysis reveals significant deviations in pitch, roll, yaw, and lateral positioning behind the swimmer even at the derived non-turbulent towing distance of at least 3.5 to 4.5 times the swimmer's body length. The device also imparts a strenuous load on the less powerful swimmers, possibly changing the mechanics of their stroke. These concerns lead to design of a new hydrodynamic drag device. This device is an elongated funnel which maintains a stable submerged position, and imparts enough load to vary velocities yet keep changes in stroke mechanics to a minimum. In this study all athletes, 9 males and 9 females ranging from division II to division I abilities, perform trials of maximal tethered and untethered sprints of two strokes with both the new and old devices. The mean active drag values obtained using the new device are 40% - 50% lower than the old device, depending on stroke. The deviation is due in part to the absence of turbulence during calibration and are accounted for with a correction factor. The remaining magnitude variation is attributed to the increased accuracy, stability and predictable fluid dynamic performance of the new device.

Determination of the active drag in swimming by means of a swimming flume

Determination of the active drag in swimming by means of a swimming flume

Active and passive drag in swimming

Active and passive drag in swimming