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- Examining the Accumulated Oxygen Deficit Method in Front Crawl SwimmingPublication . Reis, Victor M.; Marinho, Daniel; Policarpo, F. B.; Carneiro, A. L.; Baldari, C.; Silva, AntónioThe present study investigated the Accumulated Oxygen Deficit (AOD) method in front crawl swimming with the aims to assess the robustness of the oxygen uptake/swimming velocity regression line and to quantify the precision of the AOD. Twenty-nine male swimmers performed two swimming tests in different days, with a 24 h recovery between tests: a graded test and an all-out test. The all-out test was performed either in 100 m (n=11), 200 m (n=13) or 400 m (n=5). Through all testing expired gases were collected breath by breath and analysed with a K4b2 Gas Analyser (Cosmed, Rome, Italy) connected to an AquaTrainer Valve (Cosmed, Rome, Italy). The error of oxygen uptake/swimming velocity regression lines was approximately 4-5 ml x kg (-1) x min (-1)) and the regressions allowed an extrapolation of the energy cost to higher intensities with a standard error of prediction of approximately 3-4 ml x kg (-1) x min (-1). However, the data variability was considerable (95% confidence intervals of the linear extrapolation larger than 13 ml x kg (-1) x min (-1)). The AOD imprecision varied among the three distance events from approximately 3-13 ml x kg (-1). These absolute errors are small, considering the time that subjects took to cover the three distances, but relative to the AOD values that were estimated they can be considered high, especially in the 400 m bout.
- Analysis of drafting effects in swimming using computational fluid dynamicsPublication . Silva, António; Rouboa, Abel I; Moreira, António; Reis, VM; Alves, Francisco; Vilas Boas, J. Paulo; Marinho, DanielThe purpose of this study was to determine the effect of drafting distance on the drag coefficient in swimming. A k-epsilon turbulent model was implemented in the commercial code Fluent(®) and applied to the fluid flow around two swimmers in a drafting situation. Numerical simulations were conducted for various distances between swimmers (0.5-8.0 m) and swimming velocities (1.6-2.0 m.s(-1)). Drag coefficient (Cd) was computed for each one of the distances and velocities. We found that the drag coefficient of the leading swimmer decreased as the flow velocity increased. The relative drag coefficient of the back swimmer was lower (about 56% of the leading swimmer) for the smallest inter-swimmer distance (0.5 m). This value increased progressively until the distance between swimmers reached 6.0 m, where the relative drag coefficient of the back swimmer was about 84% of the leading swimmer. The results indicated that the Cd of the back swimmer was equal to that of the leading swimmer at distances ranging from 6.45 to 8. 90 m. We conclude that these distances allow the swimmers to be in the same hydrodynamic conditions during training and competitions. Key pointsThe drag coefficient of the leading swimmer decreased as the flow velocity increased.The relative drag coefficient of the back swimmer was least (about 56% of the leading swimmer) for the smallest inter-swimmer distance (0.5 m).The drag coefficient values of both swimmers in drafting were equal to distances ranging between 6.45 m and 8.90 m, considering the different flow velocities.The numerical simulation techniques could be a good approach to enable the analysis of the fluid forces around objects in water, as it happens in swimming.
- Does combined dry land strength and aerobic training inhibit performance of young competitive swimmers?Publication . Garrido, Nuno; Marinho, Daniel; Reis, VM; Tillaar, Roland Van Den; Costa, Aldo M.; Silva, António; Marques, MCThe aim of the current study was twofold: (i) to examine the effects of eight weeks of combined dry land strength and aerobic swimming training for increasing upper and lower body strength, power and swimming performance in young competitive swimmers and, (ii) to assess the effects of a detraining period (strength training cessation) on strength and swimming performance. The participants were divided into two groups: an experimental group (eight boys and four girls) and a control group (six boys and five girls). Apart from normal practice sessions (six training units per week of 1 h and 30 min per day), the experimental group underwent eight weeks (two sessions per week) of strength training. The principal strength exercises were the bench press, the leg extension, and two power exercises such as countermovement jump and medicine ball throwing. Immediately following this strength training program, all the swimmers undertook a 6 week detraining period, maintaining the normal swimming program, without any strength training. Swimming (25 m and 50 m performances, and hydrodynamic drag values), and strength (bench press and leg extension) and power (throwing medicine ball and countermovement jump) performances were tested in three moments: (i) before the experimental period, (ii) after eight weeks of combined strength and swimming training, and (iii) after the six weeks of detraining period. Both experimental and control groups were evaluated. A combined strength and aerobic swimming training allow dry land strength developments in young swimmers. The main data can not clearly state that strength training allowed an enhancement in swimming performance, although a tendency to improve sprint performance due to strength training was noticed. The detraining period showed that, although strength parameters remained stable, swimming performance still improved.
- Analysis of wind velocity and release angle effects on discus throw using computational fluid dynamicsPublication . Rouboa, Abel I; Reis, Vitor M.; Mantha, Vishveshwar R.; Marinho, Daniel A.; Silva, António J.The aim of this paper is to study the aerodynamics of discus throw. A comparison of numerical and experimental performance of discus throw with and without rotation was carried out using the analysis of lift and drag coefficients. Initial velocity corresponding to variation angle of around 35.5° was simulated. Boundary condition, on the top and bottom boundary edges of computational domain, was imposed in order to eliminate external influences on the discus; a wind resistance was calculated for the velocity values of 25 and 27 m/s. The results indicate that the flight distance (D) was strongly affected by the drag coefficient, the initial velocity, the release angle and the direction of wind velocity. It was observed that these variables change as a function of discus rotation. In this study, results indicate a good agreement of D between experimental values and numerical results.
- The use of neural network technology to model swimming performancePublication . Silva, António; Costa, Aldo M.; Oliveira, Paulo Moura; Reis, VM; Saavedra, Jose M; Perl, Jurgen; Rouboa, Abel I; Marinho, Danielto identify the factors which are able to explain the performance in the 200 meters individual medley and 400 meters front crawl events in young swimmers, to model the performance in those events using non-linear mathematic methods through artificial neural networks (multi-layer perceptrons) and to assess the neural network models precision to predict the performance. A sample of 138 young swimmers (65 males and 73 females) of national level was submitted to a test battery comprising four different domains: kinanthropometric evaluation, dry land functional evaluation (strength and flexibility), swimming functional evaluation (hydrodynamics, hydrostatic and bioenergetics characteristics) and swimming technique evaluation. To establish a profile of the young swimmer non-linear combinations between preponderant variables for each gender and swim performance in the 200 meters medley and 400 meters font crawl events were developed. For this purpose a feed forward neural network was used (Multilayer Perceptron) with three neurons in a single hidden layer. The prognosis precision of the model (error lower than 0.8% between true and estimated performances) is supported by recent evidence. Therefore, we consider that the neural network tool can be a good approach in the resolution of complex problems such as performance modeling and the talent identification in swimming and, possibly, in a wide variety of sports. Key pointsThe non-linear analysis resulting from the use of feed forward neural network allowed us the development of four performance models.The mean difference between the true and estimated results performed by each one of the four neural network models constructed was low.The neural network tool can be a good approach in the resolution of the performance modeling as an alternative to the standard statistical models that presume well-defined distributions and independence among all inputs.The use of neural networks for sports sciences application allowed us to create very realistic models for swimming performance prediction based on previous selected criterions that were related with the dependent variable (performance).
- Can the curriculum be used to estimate critical velocity in young competitive swimmers?Publication . Costa, Aldo M.; Silva, António; Louro, Hugo; Reis, VM; Garrido, Nuno; Marques, MC; Marinho, DanielThe aims of the present study were to assess critical velocity using the swimmer curriculum in front crawl events and to compare critical velocity to the velocity corresponding to a 4 mmol·l(-1) of blood lactate concentration and to the velocity of a 30 min test. The sample included 24 high level male swimmers ranged between 14 and 16 years old. For each subject the critical velocity, the velocity corresponding to a 4 mmol·l(-1) of blood lactate concentration and the mean velocity of a 30 min test were determined. The critical velocity was also estimated by considering the best performance of a swimmer over several distances based on the swimmer curriculum. Critical velocity including 100, 200 and 400 m events was not different from the velocity of 4 mmol·l(-1) of blood lactate concentration. Critical velocity including all the swimmer events was not different from the velocity of a 30 min test. The assessment of critical velocity based upon the swimmer curriculum would therefore seem to be a good approach to determine the aerobic ability of a swimmer. The selection of the events to be included in critical velocity assessment must be a main concern in the evaluation of the swimmer. Key pointsCritical velocity using 100, 200 and 400 m events was not different from the velocity of 4 mmol·l(-1) of blood lactate concentration.Critical velocity using all the swimmer events was not different from the velocity of a 30 min test.The assessment of critical velocity based upon the swimmer curriculum seemed to be a good approach to determine the aerobic capacity of a swimmer.The decision on the events to be analysed must be a main concern in the evaluation of the swimmer critical velocity.
- Physiological assessment of head-out aquatic exercises in healthy subjects: a qualitative reviewPublication . Barbosa, Tiago M.; Marinho, Daniel; Reis, VM; Silva, António; Bragada, JoséIn the last decades head-out aquatic exercises became one of the most important physical activities within the health system. Massive research has been produced throughout these decades in order to better understand the role of head-out aquatic exercises in populations' health. Such studies aimed to obtain comprehensive knowledge about the acute and chronic response of subjects performing head-out aquatic exercises. For that, it is assumed that chronic adaptations represent the accumulation of acute responses during each aquatic session. The purpose of this study was to describe the "state of the art "about physiological assessment of head-out aquatic exercises based on acute and chronic adaptations in healthy subjects based on a qualitative review. The main findings about acute response of head-out aquatic exercise according to water temperature, water depth, type of exercise, additional equipment used, body segments exercising and music cadence will be described. In what concerns chronic adaptations, the main results related to cardiovascular and metabolic adaptations, muscular strength, flexibility and body composition improvements will be reported. Key pointsSeveral papers reported consistent and significant improvement in physical fitness (e.g., aerobic capacity, muscular strength, flexibility and body composition) after a program of head-out aquatic exercise with at least eight weeks.Chronic adaptations to head-out aquatic exercise programs are the cumulative result of appropriate acute responses during the exercise session.Appropriate acute adaptations can be obtained taking into account the water temperature, water depth, type of exercise and its variants, the equipment used and the segmental cadence according to the subjects' profile.
- Hydrodynamic analysis of different thumb positions in swimmingPublication . Marinho, Daniel; Rouboa, Abel I; Alves, Francisco; Vilas Boas, J. Paulo; Machado, Leandro; Reis, VM; Silva, AntónioThe aim of the present study was to analyze the hydrodynamic characteristics of a true model of a swimmer hand with the thumb in different positions using numerical simulation techniques. A three-dimensional domain was created to simulate the fluid flow around three models of a swimmer hand, with the thumb in different positions: thumb fully abducted, partially abducted, and adducted. These three hand models were obtained through computerized tomography scans of an Olympic swimmer hand. Steady-state computational fluid dynamics analyses were performed using the Fluent(®) code. The forces estimated in each of the three hand models were decomposed into drag and lift coefficients. Angles of attack of hand models of 0°, 45° and 90°, with a sweep back angle of 0° were used for the calculations. The results showed that the position with the thumb adducted presented slightly higher values of drag coefficient compared with thumb abducted positions. Moreover, the position with the thumb fully abducted allowed increasing the lift coefficient of the hand at angles of attack of 0° and 45°. These results suggested that, for hand models in which the lift force can play an important role, the abduction of the thumb may be better, whereas at higher angles of attack, in which the drag force is dominant, the adduction of the thumb may be preferable. Key pointsNumerical simulation techniques can provide answers to problems which have been unobtainable using experimental methods.The computer tomography scans allowed the creation of a complete and true digital anatomic model of a swimmer hand.The position with the thumb adducted presented slightly higher values of drag coefficient than the positions with the thumb abducted.The position with the thumb fully abducted allowed increasing the lift coefficient of the hand at angles of attack of 0 and 45 degrees.For hand positions in which the lift force can play an important role the abduction of the thumb may be better whereas at higher angles of attack, in which the drag force is dominant, the adduction of the thumb may be preferable for swimmers.
- Swimming propulsion forces are enhanced by a small finger spreadPublication . Marinho, Daniel; Barbosa, Tiago M.; Reis, Victor M; Kjendlie, Per L; Alves, Francisco; Vilas Boas, J. Paulo; Machado, Leandro; Silva, António; Rouboa, Abel IThe main aim of this study was to investigate the effect of finger spread on the propulsive force production in swimming using computational fluid dynamics. Computer tomography scans of an Olympic swimmer hand were conducted. This procedure involved three models of the hand with differing finger spreads: fingers closed together (no spread), fingers with a small (0.32 cm) spread, and fingers with large (0.64 cm) spread. Steady-state computational fluid dynamics analyses were performed using the Fluent code. The measured forces on the hand models were decomposed into drag and lift coefficients. For hand models, angles of attack of 0 degrees, 15 degrees, 30 degrees, 45 degrees, 60 degrees, 75 degrees, and 90 degrees, with a sweep back angle of 0 degrees, were used for the calculations. The results showed that the model with a small spread between fingers presented higher values of drag coefficient than did the models with fingers closed and fingers with a large spread. One can note that the drag coefficient presented the highest values for an attack angle of 90 degrees in the three hand models. The lift coefficient resembled a sinusoidal curve across the attack angle. The values for the lift coefficient presented few differences among the three models, for a given attack angle. These results suggested that fingers slightly spread could allow the hand to create more propulsive force during swimming.
- Effects of musical cadence in the acute physiologic adaptations to head-out aquatic exercisesPublication . Barbosa, Tiago M.; Sousa, Vítor F; Silva, António; Reis, Victor M; Marinho, Daniel; Bragada, JoséThe purpose of this study was to analyze the relationships between musical cadence and the physiologic adaptations to basic head-out aquatic exercises. Fifteen young and clinically healthy women performed, immersed to the breast, a cardiovascular aquatic exercise called the "rocking horse." The study design included an intermittent and progressive protocol starting at a 90 b.min(-1) rhythm and increasing every 6 minutes, by 15 b.min(-1), up to 195 b.min(-1) or exhaustion. The rating of perceived effort (RPE) at the maximal heart rate achieved during each bout (HRmax), the percentage of the maximal theoretical heart rate estimated (%HRmax), and the blood lactate concentration ([La-]) were evaluated. The musical cadence was also calculated at 4 mmol.L(-1) of blood lactate (R4), the RPE at R4 (RPE@R4), the HR at R4 (HR@R4), and the %HRmax at R4 (%HRmax@R4). Strong relationships were verified between the musical cadence and the RPE (R2 = 0.85; p < 0.01), the HRmax (R2 = 0.66; p < 0.01), the %HRmax (R = 0.61; p < 0.01), and the [La-] (R2 = 0.54; p < 0.01). The R4 was 148.13 +/- 17.53 b.min, the RPE@R4 was 14.53 +/- 2.53, the HR@R4 was 169.33 +/- 12.06 b.min, and the %HRmax@R4 was 85.53 +/- 5.72%. The main conclusion is that increasing musical cadence created an increase in the physiologic response. Therefore, instructors must choose musical cadences according to the goals of the session they are conducting to achieve the desired intensity.