scholarly journals Drag Characteristics of Competitive Swimming Children and Adults

2008 ◽  
Vol 24 (1) ◽  
pp. 35-42 ◽  
Author(s):  
Per-Ludvik Kjendlie ◽  
Robert Keig Stallman
Keyword(s):  
Perturbation Method ◽  
Froude Number ◽  
Wave Drag ◽  
Maximal Velocity ◽  
Evaluation Tool ◽  
Competitive Swimming ◽  
Velocity Decay ◽  
Competitive Swimmers ◽  
Drag Factor ◽  
Swimming Technique

The aims of this study were to compare drag in swimming children and adults, quantify technique using the technique drag index (TDI), and use the Froude number (Fr) to study whether children or adults reach hull speed at maximal velocity (vmax). Active and passive drag was measured by the perturbation method and a velocity decay method, respectively, including 9 children aged 11.7 ± 0.8 and 13 adults aged 21.4 ± 3.7. The children had significantly lower active (kAD) and passive drag factor (kPD) compared with the adults. TDI (kAD/kPD) could not detect any differences in swimming technique between the two groups, owing to the adults swimming maximally at a higher Fr, increasing the wave drag component, and masking the effect of better technique. The children were found not to reach hull speed atvmax, and their Fr were 0.37 ± 0.01 vs. the adults 0.42 ± 0.01, indicating adults’ larger wave-making component of resistance atvmaxcompared with children. Fr is proposed as an evaluation tool for competitive swimmers.

scholarly journals Prediction of Shoulder Pain in Youth Competitive Swimmers: The Development and Internal Validation of a Prognostic Prediction Model

2020 ◽  
Vol 49 (1) ◽  
pp. 154-161
Author(s):  
Stef Feijen ◽  
Thomas Struyf ◽  
Kevin Kuppens ◽  
Angela Tate ◽  
Filip Struyf
Keyword(s):  
Logistic Regression ◽  
Shoulder Pain ◽  
Muscle Endurance ◽  
Internal Validation ◽  
Competitive Swimming ◽  
Final Model ◽  
Shoulder Muscle ◽  
Multivariable Logistic Regression ◽  
Posterior Shoulder ◽  
Competitive Swimmers

Background: Knowledge of predictors for shoulder pain in swimmers can assist professionals working with the athlete in developing optimal prevention strategies. However, study methodology and limited available data have constrained a comprehensive understanding of which factors cause shoulder pain. Purpose: To investigate risk factors and develop and internally validate a multivariable prognostic model for the prediction of shoulder pain in swimmers. Study Design: Cohort study; Level of evidence, 2. Methods: A total of 201 pain-free club- to international-level competitive swimmers were followed for 2 consecutive seasons. The cohort consisted of 96 male (mean ± SD age, 13.9 ± 2.2 years) and 105 female (13.9 ± 2.2 years) swimmers. Demographic, sport-specific, and musculoskeletal characteristics were assessed every 6 months. Swim-training exposure was observed prospectively. Shoulder pain interfering with training was the primary outcome. Multiple imputation was used to cope with missing data. The final model was estimated using multivariable logistic regression. We applied bootstrapping to internally validate the model and correct for overoptimism. Results: A total of 42 new cases of shoulder pain were recorded during the study. Average duration of follow-up was 1.1 years. Predictors included in the final model were acute:chronic workload ratio (odds ratio [OR], 4.31; 95% CI, 1.00-18.54), competitive level (OR, 0.19; 95% CI, 0.06-0.63), shoulder flexion range of motion, posterior shoulder muscle endurance (OR, 0.96; 95% CI, 0.92-0.99), and hand entry position error (OR, 0.37; 95% CI, 0.16-0.91). After internal validation, this model maintained good calibration and discriminative power (area under the receiver operating characteristic curve, 0.71; 95% CI, 0.60-0.94). Conclusion: Our model consists of parameters that are readily measurable in a swimming setting, allowing the identification of swimmers at risk for shoulder pain. Multivariable logistic regression showed the strongest predictors for shoulder pain were regional competitive swimming level, acute:chronic workload ratio, posterior shoulder muscle endurance, and hand entry error.

scholarly journals Steady hydrodynamic interaction between human swimmers

2019 ◽  
Vol 16 (150) ◽  
pp. 20180768 ◽  
Author(s):  
Zhi-Ming Yuan ◽  
Mingxin Li ◽  
Chun-Yan Ji ◽  
Liang Li ◽  
Laibing Jia ◽  
...  
Keyword(s):  
Drag Reduction ◽  
Hydrodynamic Interaction ◽  
Surface Effect ◽  
Swimming Performance ◽  
Interactive Effect ◽  
Free Water ◽  
Wave Drag ◽  
Competitive Swimming ◽  
Flow Solver ◽  
Wave Interference

This study focuses on the hydrodynamic interaction between two or three human swimmers in competitive swimming. Although the swimming performance of a single swimmer has been widely examined, studies on the interaction between multiple competitive swimmers are very rare. Experiments showed evidence that the drag of a swimmer could be modified by the existence of the other adjacent competitors (Chatard & Wilson. 2003 Med. Sci. Sports Exerc . 35 , 1176–1181. ( doi:10.1249/01.MSS.0000074564.06106.1F )). The following questions arise: (1) what mechanism determines the interaction; (2) which position experiences drag reduction or drag increase; (3) how much can drag be reduced or increased in a formation? According to the authors' knowledge, such questions have not been addressed by any published literature. Therefore, the main purpose of this study is to find the mechanism of the hydrodynamic interaction between human swimmers and to quantify this interactive effect by using a steady potential flow solver. The free-surface effect was fully taken into account in our calculations. We firstly calculated the wave drag of a swimmer swimming solely in an open swimming pool. Then we calculated the wave drag of the same swimmer when he/she swam in the wake region of one or two leading swimmers. The results showed that the hydrodynamic interaction made a significant contribution to the drafter's wave drag. By following a leading swimmer, a drafter at wave-riding positions could save up to 63% of their wave drag at speed of 2.0 m s −1 and lateral separation of 2.0 m. Particularly, when a drafter is following two side-by-side leaders, the drag reduction could even be doubled. To the authors' knowledge, this study is the first to demonstrate that the hydrodynamic interaction between human swimmers can best be described and explained in terms of wave interference effect on the free water surface. When the wave cancellation effect is observed, the wave drag of a drafter could be minimized, and this wave cancellation effect can be achieved only when the drafter is in a wave-riding position.

Blood Lactate Concentration and Clearance in Elite Swimmers During Competition

2011 ◽  
Vol 6 (1) ◽  
pp. 106-117 ◽  
Author(s):  
Jason D. Vescovi ◽  
Olesya Falenchuk ◽  
Greg D. Wells
Keyword(s):  
Blood Lactate ◽  
Lactate Concentration ◽  
Blood Lactate Concentration ◽  
Active Recovery ◽  
Competitive Swimming ◽  
Elite Swimmers ◽  
Lactate Removal ◽  
The Relationship ◽  
Competitive Swimmers ◽  
Effect Of Age

Purpose:Blood lactate concentration, [BLa], after swimming events might be influenced by demographic features and characteristics of the swim race, whereas active recovery enhances blood lactate removal. Our aims were to (1) examine how sex, age, race distance, and swim stroke influenced [BLa] after competitive swimming events and (2) develop a practical model based on recovery swim distance to optimize blood lactate removal.Methods:We retrospectively analyzed postrace [BLa] from 100 swimmers who competed in the finals at the Canadian Swim Championships. [BLa] was also assessed repeatedly during the active recovery. Generalized estimating equations were used to evaluate the relationship between postrace [BLa] with independent variables.Results:Postrace [BLa] was highest following 100–200 m events and lowest after 50 and 1500 m races. A sex effect for postrace [BLa] was observed only for freestyle events. There was a negligible effect of age on postrace [BLa]. A model was developed to estimate an expected change in [BLa] during active recovery (male = 0; female = 1): [BLa] change after active recovery = –3.374 + (1.162 × sex) + (0.789 × postrace [BLa]) + (0.003 × active recovery distance).Conclusions:These findings indicate that swimmers competing at an elite standard display similar postrace [BLa] and that there is little effect of age on postrace [BLa] in competitive swimmers aged 14 to 29 y.

Flow past a sphere moving vertically in a stratified diffusive fluid

2000 ◽  
Vol 417 ◽  
pp. 211-236 ◽  
Author(s):  
C. R. TORRES ◽  
H. HANAZAKI ◽  
J. OCHOA ◽  
J. CASTILLO ◽  
M. VAN WOERT
Keyword(s):  
Froude Number ◽  
Rear Surface ◽  
Wave Drag ◽  
Thin Layers ◽  
Original Position ◽  
Linear Wave ◽  
Frictional Drag ◽  
Pressure Drag ◽  
Lee Wave ◽  
Vertical Jet

Numerical studies are described of the flows generated by a sphere moving vertically in a uniformly stratified fluid. It is found that the axisymmetric standing vortex usually found in homogeneous fluids at moderate Reynolds numbers (25 [les ] Re [les ] 200) is completely collapsed by stable stratification, generating a strong vertical jet. This is consistent with our experimental visualizations. For Re = 200 the complete collapse of the vortex occurs at Froude number F ≃ 19, and the critical Froude number decreases slowly as Re increases. The Froude number and the Reynolds number are here defined by F = W/Na and Re = 2Wa/v, with W being the descent velocity of the sphere, N the Brunt–Väisälä frequency, a the radius of the sphere and v the kinematic viscosity coefficient. The inviscid processes, including the generation of the vertical jet, have been investigated by Eames & Hunt (1997) in the context of weak stratification without buoyancy effects. They showed the existence of a singularity of vorticity and density gradient on the rear axis of the flow and also the impossibility of realizing a steady state. When there is no density diffusion, all the isopycnal surfaces which existed initially in front of the sphere accumulate very near the front surface because of density conservation and the fluid in those thin layers generates a rear jet when returning to its original position. In the present study, however, the fluid has diffusivity and the buoyancy effects also exist. The density diffusion prevents the extreme piling up of the isopycnal surfaces and allows the existence of a steady solution, preventing the generation of a singularity or a jet. On the other hand, the buoyancy effect works to increase the vertical velocity to the rear of the sphere by converting the potential energy to vertical kinetic energy, leading to the formation of a strong jet. We found that the collapse of the vortex and the generation of the jet occurs at much weaker stratifications than those necessary for the generation of strong lee waves, showing that jet formation is independent of the internal waves. At low Froude numbers (F [les ] 2) the lee wave patterns showed good agreement with the linear wave theory and the previous experiments by Mowbray & Rarity (1967). At very low Froude numbers (F [les ] 1) the drag on a sphere increases rapidly, partly due to the lee wave drag but mainly due to the large velocity of the jet. The jet causes a reduction of the pressure on the rear surface of the sphere, which leads to the increase of pressure drag. High velocity is induced also just outside the boundary layer of the sphere so that the frictional drag increases even more significantly than the pressure drag.

scholarly journals On the Diurnal Variation of Mountain Waves

2008 ◽  
Vol 65 (4) ◽  
pp. 1360-1377 ◽  
Author(s):  
Qingfang Jiang ◽  
James D. Doyle
Keyword(s):  
Diurnal Variation ◽  
Froude Number ◽  
Flow Pattern ◽  
Surface Wind ◽  
Wave Drag ◽  
Prediction System ◽  
Wind Maximum ◽  
Mountain Waves ◽  
Ridge Crest ◽  
Deep Well

Abstract The diurnal variation of mountain waves and wave drag associated with flow past mesoscale ridges has been examined using the Coupled Ocean–Atmosphere Mesoscale Prediction System (COAMPS) and an analytical boundary layer (BL) model. The wave drag exhibits substantial diurnal variation in response to the change in the atmospheric BL characteristics, such as the BL depth, shape factor, and stability. During daytime, a convective BL develops, characterized by a shallow shear layer near the surface and a deep well-mixed layer aloft, both of which tend to decrease the wave drag. As a result, the convective BL could significantly weaken mountain waves and reduce the momentum flux by up to 90%. Near the surface, the flow pattern resembles a potential flow with a surface wind maximum located near the ridge crest. During nighttime, a shallow stable BL develops, and the modulation of wave drag by the stable nocturnal BL is governed by the BL Froude number (Fr). If the BL flow is supercritical, the drag increases as Fr decreases toward unity and reaches the maximum around Fr = 1, where the drag could be several times larger than the corresponding free-slip hydrostatic wave drag. If the BL flow is subcritical because of excessive cooling, the drag decreases with decreasing Froude number and the flow pattern near the surface resembles a typical subcritical solution with the wind maximum located near the ridge crest.

scholarly journals Swimmers Are At Risk For Stress Fractures? A Systematic Review

2018 ◽  
Vol 6 (3) ◽  
pp. 25 ◽  
Author(s):  
Angelo V. Vasiliadis ◽  
Vasileios Lampridis ◽  
Dimitrios Georgiannos ◽  
Ilias Bisbinas
Keyword(s):  
Systematic Review ◽  
Stress Fracture ◽  
Weight Bearing ◽  
Sport Activity ◽  
Stress Fractures ◽  
Extrinsic Factors ◽  
Rare Type ◽  
Stress Injury ◽  
Competitive Swimming ◽  
Competitive Swimmers

Background: Stress fractures occur most commonly in the weight-bearing bones of the lower extremities. Swimming, a non-weight-bearing activity, is a potential activity form which associated with stress fractures? Objective: This systematic review aims to provide an answer in the above question and also to identify the reported cases of stress fractures among swimmers. Method: A systematic and comprehensive search was conducted using PubMed and Research Gate databases before January 2017. The search process was completed using the keywords: “stress fracture”, “stress injury”, “fatigue fracture”, “swimming” and “swimmers”. Results: There have been only 10 studies describing stress fractures in swimmers. This rare type of injury is commonly diagnosed in the ribs of young competitive swimmers, irrespective of their preferred swimming stroke. The etiology is multifactorial and includes a combination of intrinsic and/or extrinsic factors. Conclusion: Although any sport activity can potential cause a stress fracture, competitive swimming seems to be relatively safe in this respect. Rib stress fractures appear as the most common stress fracture in competitive swimmers that clinicians should consider. A prompt diagnosis can shorten the time required for healing and decrease the risk of complication.

scholarly journals Talent Selection and Management in View of Relative Age: the Case of Swimming

2018 ◽  
Vol 80 (1) ◽  
pp. 57-67
Author(s):  
Nikoletta Nagy ◽  
Gyöngyi Földesi ◽  
Csaba Sós ◽  
Csaba Ökrös
Keyword(s):  
Talent Management ◽  
Potential Effect ◽  
Management Program ◽  
Chi Square ◽  
Competitive Swimming ◽  
Relative Age ◽  
Talent Selection ◽  
Highly Sensitive ◽  
Research Population ◽  
Competitive Swimmers

AbstractBased on our empirical research, through the analysis of the birthdates of young competitive swimmers, the present paper aims to examine the system of talent selection and management in Hungarian competitive swimming complemented with a new element. The research population consisted of the registered junior competitive swimmers participating in the new talent management program of the Hungarian Swimming Association (N=235; average age: 11.44) due to the decision of the Coaches’ Committee. Our research was based on the analysis of documents and databases. Besides the descriptive statistics, Chi-square tests and the Kruskal-Wallis test were applied. The results show that swimmers born in the first three months of the year are still more likely to be recruited in the program than their relatively younger counterparts. Furthermore, as a potential effect of the new program, the dominance of the first quarter of the year is also characteristic among those eligible for the next level of talent management. The new selection system of Hungarian swimmers is still highly sensitive to the relative age. Thus, it is recommended to further investigate the functioning of the new talent management program in terms of selection and success.

scholarly journals Gender effect on underwater undulatory swimming technique of young competitive swimmers

2019 ◽  
Vol 21 (4) ◽  
Author(s):  
Łukasz Wądrzyk ◽  
Robert Staszkiewicz ◽  
Łukasz Kryst ◽  
Magdalena Żegleń
Keyword(s):  
Gender Effect ◽  
Undulatory Swimming ◽  
Competitive Swimmers ◽  
Swimming Technique

The Effects of Applied and Sport-Specific Mindful Sport Performance Enhancement Training on Mindfulness Skills, Flow, and Emotional Regulation in National Competitive Swimmers

2021 ◽  
Vol 5 (1) ◽  
pp. 114-123
Author(s):  
Jenny Meggs ◽  
Mark Chen
Keyword(s):  
Emotional Regulation ◽  
Relaxation Training ◽  
Performance Enhancement ◽  
Swimming Performance ◽  
Sport Performance ◽  
Control Group ◽  
Second Phase ◽  
Competitive Swimming ◽  
Mindfulness Skills ◽  
Competitive Swimmers

These case studies examined the effects of mindful sport performance enhancement (MSPE) programs on competitive swimming performance, flow experience, and emotional regulation. Sixteen national competitive adolescent swimmers were randomly allocated into MSPE (n = 9) and relaxation training (n = 7) groups for 8 weeks. In the second phase of the intervention, the 16 participants were evenly split into an MSPE group for swimming and a control group for 5 weeks. The participants completed measures of trait and state flow, and mindfulness pre- and postintervention. The data analysis revealed that mindfulness had significant effects on both action–awareness merging and clear goals subscales. Further analysis revealed that the MSPE for swimming group significantly improved in terms of presence relative to the control group. In conclusion, general and sport-specific mindfulness interventions can psychologically benefit adolescent competitive swimmers.

Free-Surface Effects of Yacht Appendages

2002 ◽  
Vol 46 (01) ◽  
pp. 31-38
Author(s):  
P.S. Jackson ◽  
G. Marr
Keyword(s):  
Free Surface ◽  
Froude Number ◽  
Surface Effects ◽  
Wave Drag ◽  
Panel Method ◽  
The Third

This paper uses a panel method based on Kelvin sources and doublets to explore the interactions between the free surface and yacht hull appendages. The emphasis is on understanding the physical origins of the kinds of effects observed in tank tests and in trying to confirm or improve the methods used to predict these effects. Three kinds of interaction are explored, the first being the effect of Froude number, heel and leeway on sideforce, the second being the subsequent effects of residuary resistance due to appendages, and the third being the change in wave drag associated with the presence of a ballast bulb at zero heel and leeway.

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