Nonlinear Analysis of the Hand and Foot Force-Time Profiles in the Four Competitive Swimming Strokes.

Human locomotion on water depends on the force produced by the swimmer to propel the body forward. Performance of highly complex motor tasks like swimming can yield minor variations that only nonlinear analysis can be sensitive enough to detect. The purpose of the present study was to examine the nonlinear properties of the hand/feet forces and describe their variations across the four competitive swimming strokes performing segmental and full-body swimming. Swimmers performed all-out bouts of 25 m in the four swimming strokes, swimming the full-body stroke, with the arm-pull only and with the leg kicking only. Hand/foot force and swimming velocity were measured. The Higuchi's fractal dimension (HFD) and sample entropy (SampEn) were used for the nonlinear analysis of force and velocity. Both the arm-pull and leg kicking alone were found to produce similar peak and mean hand/foot forces as swimming the full-body stroke. Hand force was more complex in breaststroke and butterfly stroke; conversely, kicking conditions were more complex in front crawl and backstroke. Moreover, the arm-pull and kicking alone tended to be more complex (higher HFD) but more predictable (lower SampEn) than while swimming the full-body stroke. There was no loss of force production from segmental swimming to the full-body counterpart. In conclusion, the number of segments in action influences the nonlinear behavior of the force produced and, when combining the four limbs, the complexity of the hand/foot force tends to decrease.

V ˙ O 2 kinetics and tethered strength influence the 200-m front crawl stroke kinematics and speed in young male swimmers.

Background: The aim of this research was to examine the relationship between the fast component of oxygen consumption developed in 1-min V ˙ O 2 and force indices both measured in tethered swimming test and to assess the influence of the gathered indices on speed and swimming kinematics in 200-m front crawl race. Methods: Forty-eight male swimmers (aged 13.5 ± 0.9 years old) participated in this study. Testing included 1) 1-min all-out front crawl tethered swimming while oxygen consumption (breath by breath) and tethered forces were measured, 2) 200-m front crawl race-like swimming featuring kinematic analysis, and 3) biological age (BA) examination. Results: During the 1-min all-out tethered swimming test, a linear increase in oxygen consumption was observed. There were moderate to high partial correlations between particular periods of seconds in the 1-min V ˙ O 2 : 31-60, 41-60, and 51-60 and F max, F ave , and I ave of tethered swimming, while 41-60 and 51-60 V ˙ O 2 were moderately to highly interrelated with all the swimming speed indices and SI. The swimming speed indices significantly interplayed with SL, SI, F max, F ave , and I ave . Partial correlations were computed with BA control. Conclusion: The ability of reaching a high level of V ˙ O 2 fast is essential for a swimmer's energy production at short- and middle-distance events. Reaching a high level of V ˙ O 2 significantly determines tethered strength and swimming kinematics. The level of V ˙ O 2 influences the maintenance of a proper pulling force and the stroke technique of front crawl swimming in young male swimmers.

Effect of Concurrent Resistance Training on Lower Body Strength, Leg Kick Swimming, and Sport-Specific Performance in Competitive Swimmers.

The present study investigated the effect of 9 weeks of combined resistance training (aquatic and dry land resistance) on maximum lower body strength, leg kick, and swimming performance in competitive swimmers. Twenty-two male national competitive swimmers were randomly assigned into two groups: experimental group (EG: age = 16.2 ± 0.3 years) or control group (CG: age = 16.3 ± 0.3 years). The EG performed a combined resistance training while the CG group completed their usual training. One repetition maximum (1RM) back squat, 30 m leg kick, and swimming performance (100 m front crawl, start and turn) were evaluated in pre and post test. The findings showed a significant increase in 1RM back squat (d = 1.90; 14.94 ± 1.32%) after 9 weeks of combined resistance training. In addition, ours results revealed a significant improvement in 30 m leg kick swimming (d = 2.11; 5.84 ± 0.16%) and in all swimming, start and turn performances (d = 1.83 to 2.77; 2.69 ± 0.18% to 15.14 ± 1.06%) in EG. All dependent variables remained unchanged in the CG. To sum up, 9 weeks of combined resistance training can improve the maximum lower body strength and leg kick swimming performance. These improvements can be the essential factors that subsequently positively affected swimming, start and turn performances. Combined resistance training is an effective training that can be incorporated by coaches and swimmers into their programs to improve strength, leg kick swimming, and, subsequently, swimming performance in competitive swimmers.

Applicability of an indirect VO2max test: its association with the 400 meters freestyle performance

Abstract - The aim of this study was to evaluate the VO2max using a previously validated indirect test for non-expert adult swimmers and to verify its connection with the 400 meters freestyle test. A total of 17 non-expert male swimmers (21.5 ± 3.12 years) were evaluated. Body composition measurements included body weight (74 ± 9.41 kg), height (172.9 ± 5.21 cm) and body fat percentage (15.2 ± 4.15 %). Two tests were conducted on different days; the 400 meters freestyle (400 MF) and the Progressive Swim Test (PSwT), respectively. The participant's heart rate frequency before and after the test (BHR and AHR) was analyzed, as well as the subjective perception of effort (RPE), the number of laps covered (NLP), and the time of test execution measured in minutes. Significant differences were identified in all variables (p < 0.05) with the exception of BHR. An inverse correlation (r > - 0.60) was found between AHR and execution time (r > - 0.70), as well as between the VO2max estimated by the PSwT and the 400 MF performance test (r > - 0.70). The Bland-Altman Plot showed that the values discovered were within the established concordance limits of 95% (±1.96 SD). A negative correlation between a swimming test and a test that estimates the VO2max occurred, and the PSwT showed results of greater approximation of the aerobic power of non-expert swimmers. In conclusion, the PSwT is applicable for non-expert adult swimmers.

Inclusão do equivalente do lactato sanguíneo O2 na regressão de intensidade de exercício VO2 aumenta o gasto energético de corrida e diminui sua precisão / Inclusion of blood lactate O2 equivalent in the VO2 exercise intensity regression increases the energy cost of running and lowers its precision / La inclusión del equivalente del lactato sanguíneo O2 en la regresión de intensidad de ejercicio VO2 aumenta el gasto energético de la carrera y disminuye su precisión

INTRODUÇÃO E OBJETIVOS: Investigar se a inclusão do equivalente energético de lactato sanguíneo (LS) em intensidades submáximas alteraria o gasto energético de corrida (Gc) estimado para corrida supramáxima de alta intensidade assim como sua precisão MÉTODOS: O Gc foi determinado a partir da curva de regressão de velocidade do VO2. Para cada sujeito, uma regressão alternativa foi estabelecida em que energia equivalente a 3 ml de O2 kg-1∙mM-1 de LS foi adicionada ao VO2. Testes t pareados, correlações pareadas e plotagem de Bland-Altman foram utilizados para investigar se os dois métodos representam os mesmos fenômenos. RESULTADOS: Os principais achados foram que o Gc previsto para intensidades supramáximas incluídos entre 110 e 160% ao correspondente ao pico de VO2 dos indivíduos aumentou significativamente quando as medidas de LS foram incluídas nas regressões. A inclusão das medidas de LS também aumentaram a imprecisão do Gc a 110, 120, 130, 150 e 160%. CONCLUSÃO: Nossos resultados indicam que a inclusão do equivalente do lactato de O2 na regressão de intensidade de VO2-exercício aumenta o gasto energético e diminui sua precisão.

INTRODUCTION AND OBJECTIVES: Investigate whether the inclusion of the blood lactate (BL) energy equivalent at submaximal intensities would change the energy cost of running (CR) predicted to supramaximal high-intensity running as well as its precision. METHODS: The CR was determined from the slope of the VO2-speed regression. For each subject an alternative regression was established where an energy equivalent of 3 ml O2 kg-1∙mM-1 BL was added to the VO2. Paired t-tests, pairwise correlations and Bland-Altman plots were used to investigate whether the two methods represent the same phenomena. RESULTS: The main findings were that CR predicted to supramaximal intensities comprised between 110% and 160% of that corresponding to the individuals' peak VO2, increased significantly when the BL measurements were included in the regressions. The inclusion of BL measurements also increased the imprecision of the CR at 110%, 120%, 130%, 150% and 160%. CONCLUSIONS: Our results indicate that inclusion of lactate O2 equivalent in the VO2-exercise intensity regression increases the energy cost of running and lowers its precision.

INTRODUCCIÓN Y OBJETIVOS: Investigar si la inclusión del equivalente energético de lactato sanguíneo (LS), en intensidades submáximas, modificaría el gasto energético de la carrera (Gc), estimado para carrera supramáxima de alta intensidad, así como su precisión. MÉTODOS: El Gc fue determinado a partir de la curva de regresión de velocidad del VO2. Para cada individuo, se estableció una regresión alternativa en la cual energía equivalente a 3 ml de O2 kg-1∙mM-1 de LS fue adicionada al VO2. Pruebas t por pares, correlaciones por pares y plotaje de Bland-Altman fueron utilizados para investigar si los dos métodos representan los mismos fenómenos. RESULTADOS: Los hallazgos principales fueron que el Gc previsto para intensidades supramáximas, incluidos 110% y 160% de lo que corresponde al pico de VO2 de los individuos, aumentó significativamente cuando las medidas de LS fueron incluidas en las regresiones. La inclusión de las medidas de LS también aumentó la imprecisión del Gc a 110%, 120%, 130%, 150% y 160%. CONCLUSIÓN: Nuestros resultados indican que la inclusión del equivalente del lactato de O2, en la regresión de intensidad de VO2-ejercicio, aumenta el gasto energético y disminuye su precisión.

Validation of an equation for estimating maximal oxygen consumption of nonexpert adult swimmers.

OBJECTIVE: To validate an equation to estimate the maximal oxygen consumption (VO2max) of nonexpert adult swimmers. METHODS: Participants were 22 nonexpert swimmers, male, aged between 18 and 30 years (age: 23.1 ± 3:59 years; body mass: 73.6 ± 7:39 kg; height 176.6 ± 5.53 cm; and body fat percentage: 15.9% ± 4.39%), divided into two subgroups: G1 - eleven swimmers for the VO2max oximetry and modeling of the equation; and G2 - eleven swimmers for application of the equation modeled on G1 and verification of their validation. The test used was the adapted Progressive Swim Test, in which there occurs an increase in the intensity of the swim every two laps. For normality and homogeneity of data, Shapiro-Wilk and Levene tests were used, the descriptive values of the average and standard deviation. The statistical steps were: (1) reliability of the Progressive Swim Test - through the paired t-test, intraclass correlation coefficient (ICC), and the Pearson linear correlation (R) relative to the reproducibility, the coefficient of variation (CV), and standard error measurement (SEM) for the absolute reproducibility; (2) in the model equation to estimate VO2max, a relative VO2 was established, and a stepwise multiple regression model was performed with G1 - so the variables used were analysis of variance regression (AR), coefficient of determination (R(2)), adjusted coefficient of determination (R(2)a), standard error of estimate (SEE), and Durbin-Watson (DW); (3) validation of the equation - the results were presented in graphs, where direct (G1) and estimated (G2) VO2max were compared using independent t-test, linear regression (stressing the correlation between groups), and Bland-Altman (the bias agreement of the results). All considered a statistical significance level of P < 0.05. RESULTS: On the trustworthiness of the Progressive Swim Test adapted presented as high as observed (R and ICC > 0.80, CV < 10%, and SEM < 2%). In the equation model, VO2max has been considered the third model as recommended due to the values found (AR < 0.01, R = 0795, R(2) = 0633; R(2)a = 0.624, SEE = 7.21, DW = 2.06). Upon validation of the equation, no significant differences occurred between G1 and G2 (P > 0.01), linear regression stressed a correlation between the groups (R > 0.80, P < 0.01), and Bland-Altman plotting of the results was within the correlation limits of 1.96 (95% confidence interval). CONCLUSION: The estimating equation for VO2max for nonexpert swimmers is valid for its application through the Progressive Swim Test, providing to contribute in prescribing the swimming lessons as a method of evaluating the physical condition of its practitioners.

Validação de equações preditivas da área de secção transversa do tronco / Validation of predictive equations of the cross-sectional area of the human trunk

O objectivo do estudo foi desenvolver e validar equações preditivas da área de secção transversa do tronco humano, Os modelos foram desenvolvidos para o sexo masculino e de acordo com o nível competitivo, A amostra foi composta por 152 sujeitos, todos praticantes de Natação Pura desportiva, com idades entre os 10 e os 32 anos de idade, Para o desenvolvimento dos modelos foi utilizado um grupo de sujeitos para estimar a equação e um outro para validar. Foram avaliadas as seguintes características antropométricas: (i) massa corporal; (ii) estatura; (iii) diâmetro bi-acromial; (iv) diâmetro tóraco-sagital; (v) perímetro peitoral e (vi) área de secção transversal do tronco. Os modelos preditivos foram desenvolvidos através de análise de regressão linear múltipla passo-a-passo e num dos casos, com recurso ao nível competitivo enquanto variável dummy. Todos os modelos desenvolvidos incluíram como variáveis independentes o diâmetro tóraco-sagital e o perímetro peitoral (0,32 ≤ R² ≤ 0,48; P < 0,01). No processo de validação entre as áreas de secção transversal do tronco medida e estimada, não se verificaram diferenças significativas entre valores médios (P > 0,05), as regressões lineares simples foram moderadas (0,23 ≤ R² ≤ 0,39; 0,01 ≤ P ≤ 0,001) e o critério de Bland Altman foi em todos os casos cumprido. Pode concluir-se que os modelos desenvolvidos para nadadores masculinos, e de acordo com o nível competitivo, predizem com validade a área de secção transversa do tronco de nadadores.

The objective of this study was to develop and validate predictive equations of the cross-sectional area of the human trunk. The models were developed for males according to their level of expertise. The sample comprised 152 male subjects, all of them with a background in competitive or recreational swimming. Their ages ranged between 10 and 32 years. Two different groups of subjects were used to estimate and validate the equation. The following anthropometric characteristics were assessed: (i) body weight, (ii) height, (iii) biacromial diameter, (iv) sagittal thoracic diameter, (v) chest circumference, and (vi) cross-sectional area of the trunk. Predictive models were developed using stepwise multiple linear regression analysis. One of the models used level of expertise as a dummy variable. All models included sagittal thoracic diameter and chest circumference as independent variables (0.32 ≤ R² ≤ 0.48; P < 0.01). The validation process of the measured and estimated cross-sectional area of the trunk did not reveal any significant differences between the mean values (P > 0.05). The simple linear regressions were moderate (0.23 ≤ R² ≤ 0.55; 0.01 ≤ P ≤ 0.001), and the Bland-Altman criterion was met in all cases. Therefore, our findings suggest that the models developed for male swimmers according to their level of expertise are able to provide a valid prediction of the cross-sectional area of the trunk.

Estudo comparativo das adaptações fisiológicas agudas durante a execução de três variantes de um exercício básico de Hidroginástica / Comparison of acute physiological adaptations between three variants of a basic head-out water exercise

Foi objectivo do estudo comparar as adaptações fisiológicas agudas de variantes do mesmo exercício básico de Hidroginástica (acção exclusiva dos membros inferiores, acção simultânea dos membros inferiores e dos membros superiores, acção simultânea dos membros inferiores e dos membros superiores usando halteres flutuantes). Foram estudados 16 sujeito do sexo feminino, jovens, clinicamente saudáveis e com um nível de actividade física regular. Cada sujeito realizou, um exercício básico de Hidroginástica designado de “Cavalo-marinho”. Antes e após cada execução de 6 minutos do exercício foi avaliada a percepção subjectiva de esforço (RPE) e a lactatemia ([La-]). Antes, durante e após cada execução foi avaliada a frequência cardíaca máxima atingida durante a exercitação (FCmax) e estimada a percentagem de frequência cardíaca máxima teórica atingida durante a exercitação (%FCmax). Os sujeitos percepcionaram um aumento significativo da RPE passando da exercitação exclusiva da acção dos membros inferiores, para a exercitação simultânea dos membros inferiores e dos membros superiores, assim como, para a acção a exercitação simultânea dos membros inferiores e dos membros superiores com os halteres. O esforço cardíaco (FCmax e %FCmax) foi significativamente inferior ao realizar o exercício básico estudado apenas com acção dos membros inferiores do que nas outras variantes. O aumento de segmentos em acção e a exercitação com os halteres promoveu incrementos significativos da [La-]. Concluindo, o incremento do número de segmentos em acção simultânea, assim como, a utilização de halteres flutuantes tendem a aumentar significativamente a resposta fisiológica aguda em Hidroginástica.

The aim of this investigation was to compare the acute physiological adaptations to several variants of the same basic head-out aquatic exercise (only with legs actions, with simultaneous legs and arms actions, with simultaneous legs and arms actions using buoyancy dumb-bells). 16 young females, clinically healthy and with a regular level of physical activity were studied. Each subjected performed a basic head-out aquatic exercise named “rocking horse”. Before and after each 6 minutes exercise, rate of perceived exertion (RPE) and blood lactate (La-]) were evaluated. Before, during and after each exercise, the maximal heart rate achieved (FCmax) was measured and the percentage of maximal theoretical heart rate estimated (%FCmax). The subjects perceived an increasing exertion from the exercise only with legs actions to the exercise with simultaneous legs and arms actions, to the exercise with simultaneous legs and arms actions including dumb-bells. The cardiac workout (FCmax and %FCmax) was significantly lower performing the exercise only with the legs than in the other two exercise conditions. The increasing number of limb’s actions and the adoption of dumb-bells promoted an increase of the blood lactate. In conclusion, the increasing number of simultaneous limb’s actions and the inclusion of materials, just like buoyancy dumb-bells, increased the acute physiological response in head-out aquatic exercises.