Abstract Aim: This study aimed to verify the acute effect of photobiomodulation (PBM) on maximal lactate production rate (VLamax) in front crawl swimmers. Methods: Fifteen male swimmers (20.9 ± 2.4-year-old) participated in this study. Three sets of front crawls were performed at distances of 100-, 200- and 400-m under three experimental conditions: PBM (420 J), placebo (PLA) and control (C) in this randomized, crossover, double-blind and placebo-controlled study. PBM or PLA were applied or simulated before performance tests. One-way Anova for repeated measurements were used for statistical analyses. Results: The results showed that the prior PBM application did not affect VLamax in front crawl swimmers: VLamax 100-m (PBM = 0.20 ± 0.05 mmol·L-1·s-1; PLA = 0.20 ± 0.04 mmol·L-1·s-1 and C = 0.21 ± 0.04; mmol·L-1·s-1); 200-m (PBM = 0.09 ± 0.03 mmol·L-1·s-1; PLA = 0.08 ± 0.02 mmol·L-1·s-1 and C = 0.08 ± 0.02 mmol·L-1·s-1) and 400-m (PBM = 0.04 ± 0.01 mmol·L-1·s-1; PLA = 0.04 ± 0.01 mmol·L-1·s-1 and C = 0.03 ± 0.01 mmol·L-1·s-1). Nor effect swim time (ST) performance: ST 100 m (PBM = 65.5 ± 6.3 s; PLA = 65.2 ± 5.6 s; C = 66.0 ± 5.9 s); ST 200 m (PBM = 148.5 ± 17.9 s; PLA = 149.4 ± 16.4 s; C = 150.1 ± 17.9 s); ST 400 m (PBM = 327.7 ± 38.2 s; PLA = 321.6 ± 47.7 s; C = 329.5 ± 41.2 s). Conclusions: PBM application prior front crawl swimming tests did not significantly modify the VLamax on swimmers covering distances of 100-, 200- and 400-m.

ResumoO objetivo do estudo foi verificar a influência do nível de performance na estratégia de ritmo de corrida de corredores recreacionais. Adicionalmente, objetivou-se descrever o comportamento da frequência cardíaca (FC) obtida em prova de 10 km em pista de atletismo. Participaram 39 corredores recreacionais (31,5 ± 6,7 anos), experientes em provas de 10 km que realizaram uma performance nesta distância em pista de atletismo (400 m). A FC foi constantemente monitorada (Polar RS800) e o tempo a cada 400 m foi registrado para determinação da velocidade média (VM), posteriormente analisada a cada 2 km. Os participantes foram divididos em dois grupos de acordo com a VM alcançada nos testes: G1 = VM 10 km ≤ 11,81 (n = 20) e G2 = VM 10 km > 11,81 (n = 19). A comparação entre os valores de VM e FC obtidos nos diferentes momentos da performance para os dois grupos foi realizada pela Anova mista, adotando-se nível de significância de p < 0,05. Os valores de VM foram diferentes entre os grupos em todos os momentos analisados, com aumento significante da VM do momento 6-8 km para 8-10 km para o mesmo grupo. Os valores de FC foram diferentes apenas intra-grupos. No G1, houve aumento significante da FC a cada 2 km de prova. Para o G2, a FC aumentou do 2º ao 4º km e permaneceu estável até o 8º km, aumentando novamente nos últimos 2 km da performance. Concluímos que o nível de performance não influencia a estratégia de corrida de corredores recreacionais.

AbstractThe aim of the present study was to verify the influence of the performance level in the strategy of running pacing from recreational runners. Additionally, it was aimed to describe the heart rate (HR) responses measured in a 10-km running performance in a track. Thirty-nine recreational runners took part (31.5 ± 6.7 years), who had experience in 10-km races and realized a 10-km running performance in a track (400 m). HR was constantly monitored (Polar RS800) and the time each 400 m was registered to determine MS, and then analyzed each 2 km. Participants were divided into two groups according to their MS attained in the tests: G1 - MS 10 km ≤ 11.81 (n = 20) and G2 - MS 10 km > 11.81 (n = 19). The comparison between MS and GR obtained in different moments of the performance for both groups was made by mixed Anova for repeated measures, adopting a significance level of p < 0.05. MS values were different between the groups in all moments analyzed with a significant increase in MS from moment 6-8 km to 8-10 km for the same group. HR values were different only within-groups. In G1, there was a significant increase in HR each 2 km. For G2, HR increased from the second to the forth km and remained stable up to the eighth km, increasing again in the last 2 km of the performance. We concluded that the performance level does not influence in the running strategy of recreational runners.

The Metabolic Syndrome (MetS) is defined as a pattern of metabolic disturbances, which include central obesity, insulin resistance and hyperglycemia, dyslipidemia, and hypertension. Milk has been promoted as a healthy beverage that can improve the management of MetS. Most human adults, however, down-regulate the production of intestinal lactase after weaning. Lactase encoded by the LCT gene is necessary for lactose digestion. The -13910C > T SNP (rs4988235) is responsible for the lactase persistence phenotype in European populations. We herein investigated whether the lactase persistence genotype is also associated with the MetS in subjects from a Brazilian population of European descent. This study consisted of 334 individuals (average age of 41 years) genotyped by PCR-based methods for the -13910C > T SNP. Clinical data were assessed and the genotypes were tested for their independent contribution to the MetS using chi-square tests and multiple logistic regression analysis. Univariate analyses showed that hypertension and MetS prevalence were higher in individuals with the lactase non-persistence genotype than in lactase persistence subjects. Furthermore, lactase persistence was associated with a lower risk for MetS (OR = 0.467; 95% CI 0.264-0.824; p = 0.009). These results suggest that LCT genotypes can be a valuable tool for the management of MetS treatment.

Poucos estudos verificaram a influência do ambiente de teste (campo e laboratório) sobre o ritmo de corrida e variáveis fisiológicas obtidas durante o desempenho em corrida de endurance. Portanto, o objetivo deste estudo foi comparar o comportamento da velocidade média (VM), ritmo de corrida, frequência cardíaca (FC) e percepção subjetiva de esforço (PSE) obtidas durante os desempenhos de corrida em provas time trial de uma hora realizados em pista de atletismo e em esteira. Dezoito homens corredores recreacionais (25,4 ± 3,3 anos) realizaram duas performances de uma hora de corrida: uma em esteira e outra em pista de atletismo de 400 m. A PSE e a FC foram registradas a cada 10 minutos, e a VM a cada 15 minutos para a determinação do ritmo de corrida. As variáveis relacionadas aos desempenhos foram comparadas pelo teste t de Student para amostras pareadas. Os valores de VM, FC e PSE obtidos durante diferentes momentos das provas foram comparados pela Anova de dois fatores para medidas repetidas seguido do post hoc de Bonferroni. Para todas as análises, foi adotado nível de significância de P< 0,05. A VM da prova realizada em pista (12,2 ± 0,8 km·h-1) foi superior à prova em esteira (11,8 ± 0,8 km·h-1). Além disso, foram encontradas diferenças entre os dois desempenhos para os valores de frequência cardíaca média e máxima, e para o ritmo de corrida. A partir dessas diferenças, conclui-se que os desempenhos foram influenciados pelo ambiente onde as provas de uma hora foram realizadas.

Few studies have investigated the influence of test environment (field vs. laboratory) on pacing strategy and on physiological variables measured during endurance running performance tests. The objective of this study was therefore to compare the behavior of mean velocity (MV), pacing strategy, heart rate (HR) and rating of perceived exertion (RPE) during one-hour running time trials conducted on an athletics track with the behavior of the same variables during one-hour running time trials conducted on a treadmill. Eighteen male recreational runners (25.4 ± 3.3 years) performed two one-hour time trials; the first running on a treadmill and the second on a 400 m athletics track. Rating of perceived exertion and HR were recorded every 10 minutes and MV was calculated every 15 minutes for analysis of pacing strategy (0-15min; 15-30min; 30-45min; and 45-60min). These performance variables were compared using Student's t test for paired samples. Figures for MV, HR and RPE measured at different points during the trials were compared using two-factor ANOVA for repeated measures, followed by Bonferroni's post hoc test. A significance level of P < 0.05 was adopted for all analyses. Mean velocity was higher for the trials on the running track (12.2 ± 0.8 km·h-1) than for the trials on the treadmill (11.8 ± 0.8 km·h-1). Additionally, there were also differences between the two test environments for mean and maximum heart rate, and in terms of pacing strategy. On the basis of these differences, it can be concluded that performance was influenced by the environment in which the one-hour time trials were conducted.

Preditores de desempenho modificam-se constantemente na juventude devido ao início precoce das rotinas de treinamento sistematizado na natação. Sendo assim, o objetivo do estudo foi determinar o grupo de parâmetros que melhor prediz performances de curta e média distância em nadadores jovens de ambos os gêneros. Trinta e três nadadores competitivos de ambos os gêneros (10 a 16 anos) participaram do estudo. Foi utilizada regressão linear múltipla (RLM) considerando as velocidades médias de 100, 200 e 400m como variáveis dependentes, e cinco grupos de parâmetros como possíveis preditores (antropometria, composição corporal, parâmetros fisiológicos e biomecânicos, idade cronológica/ pilosidade pubiana). Os principais resultados revelaram poder de explicação próximo a 100% para ambos os gêneros em todas as performances, entretanto com diferentes preditores nos modelos de RLM. Logo, há consideráveis diferenças que devem ser consideradas em programas de treinamento entre preditores de performances de curta e média distância, para meninos e meninas.

Predictors of performance in adult swimmers are constantly changing during youth especially because the training routine begins even before puberty in the modality. Therefore this study aimed to determine the group of parameters that best predict short and middle swimming distance performances of young swimmers of both genders. Thirty-three 10-to 16-years-old male and female competitive swimmers participated in the study. Multiple linear regression (MLR) was used considering mean speed of maximum 100, 200 and 400 m efforts as dependent variables, and five parameters groups as possible predictors (anthropometry, body composition, physiological and biomechanical parameters, chronological age/pubic hair). The main results revealed explanatory powers of almost 100% for both genders and all performances, but with different predictors entered in MLR models of each parameter group or all variables. Thus, there are considerable differences in short and middle swimming distance, and males and females predictors that should be considered in training programs.

Predictores de rendimiento en nadadores adultos cambian constantemente en la juventud, especialmente porque la rutina de entrenamiento comienza antes de la pubertad. Por tanto, el objetivo fue determinar el conjunto de parámetros que mejor predice el rendimiento de corta y media distancia de los nadadores de ambos sexos. Participaron 33 nadadores de ambos sexos (edad, 10-16 años). Regresión lineal múltiple fue usada considerando la velocidad promedio de 100, 200 y 400m como variables dependientes, y cinco grupos de parámetros como posibles predictores (antropometría, composición corporal, parámetros fisiológicos y biomecánicos, edad/vello púbico). Los principales resultados revelan explicación cercana al 100% para ambos sexos en todas las distancias, pero con diferentes modelos de predicción para cada grupo de parámetros o con todos los parámetros. Por tanto, existen diferencias considerables entre los predictores de cortas y media distancias en los niños y niñas que deben ser considerados en los programas de entrenamiento.