Effects of a Low Dose of Orally Administered Creatine Monohydrate on Post-Fatigue Muscle Power in Young Soccer Players.

The use of creatine monohydrate (Cr) in professional soccer is widely documented. However, the effect of low doses of Cr on the physical performance of young soccer players is unknown. This study determined the effect of a low dose of orally administered Cr on muscle power after acute intra-session fatigue in young soccer players. Twenty-eight young soccer players (mean age = 17.1 ± 0.9 years) were randomly assigned to either a Cr (n = 14, 0.3 g·kg-1·day-1 for 14 days) or placebo group (n = 14), using a two-group matched, double-blind, placebo-controlled design. Before and after supplementation, participants performed 21 repetitions of 30 m (fatigue induction), and then, to measure muscle power, they performed four repetitions in half back squat (HBS) at 65% of 1RM. Statistical analysis included a two-factor ANOVA (p ˂ 0.05). Bar velocity at HBS, time: p = 0.0006, ŋp2 = 0.22; group: p = 0.0431, ŋp2 = 0.12, time × group p = 0.0744, ŋp2 = 0.02. Power at HBS, time: p = 0.0006, ŋp2 = 0.12; group: p = 0.16, ŋp2 = 0.06, time × group: p = 0.17, ŋp2 = 0.009. At the end of the study, it was found that, after the induction of acute intra-session fatigue, a low dose of Cr administered orally increases muscle power in young soccer players.

Test-retest reliability of Latin American Group for Maturity (GDLAM) protocol in older women.

Functional autonomy (FA) is a critical factor in determining the quality of life of older adults (OA), especially in the case of older women (OW), as they face a decline in FA in their later years of life. FA should be assessed early, using valid, reliable, and low-cost tests. This study evaluated the test-retest reliability of GDLAM and GDLAM autonomy index (GI) in OW. Thirty-nine OW (71.2 ± 6.50 years) participated in the study. A repeated measures design was used to compare the interday test-retest reliability of the five GDLAM tests (seconds) and the GI (points). The five tests represent activities of daily living, such as dressing or wandering around the house, while the GI provides a weighting of the results of the five tests. The analysis consisted of the intraclass correlation coefficient (ICC), standard error of measurement (SEM), and coefficient of variation (CV). A CV ≤ 10% and an ICC ≥ 0.80 were considered acceptable reliability, whereas a CV ≤ 5% and an ICC ≥ 0.90 were considered high reliability. The outcome of the five tests, represented by the GI, showed high interday test-retest reliability (CV = 6.00% and ICC = 0.91). The results of this study demonstrate that the five tests of the GDLAM protocol and the GI have high interday test-retest reliability and good interday reproducibility. From a practical point of view, the GDLAM protocol allows the assessment of FA of community-dwelling OW, providing background for early diagnosis and, with it, the possibility of developing an individualized physical exercise prescription.

Effects of acute beta-alanine supplementation on post-exertion rating of perceived exertion, heart rate, blood lactate, and physical performance on the 6-minute race test in middle-distance runners / Efectos de la suplementación aguda con beta-alanina sobre el índice de esfuerzo percibido, la frecuencia cardíaca y el lactato sanguíneo posesfuerzo, y el rendimiento físico en la prueba de carrera de 6 minutos en corredores de media distancia

Background: the use of beta-alanine (BA) to increase physical performance in the heavy-intensity domain zone (HIDZ) is widely documented. However, the effect of this amino acid on the post-exertion rating of perceived exertion (RPE), heart rate (HR), and blood lactate (BL) is still uncertain. Objectives: a) to determine the effect of acute BA supplementation on post-exertion RPE, HR, and BL in middle-distance athletes; and b) todetermine the effect of acute BA supplementation on physical performance on the 6-minute race test (6-MRT). Material and methods: the study included 12 male middle-distance athletes. The design was quasi-experimental, intrasubject, double-blind& crossover. It had two treatments (low-dose BA [30 mg·kg-1] and high-dose BA [45 mg·kg-1]) and a placebo, 72 hours apart. The effect of BA was evaluated at the end of the 6-MRT and post-exertion. The variables were RPE, HR and BL, and 6-MRT (m) distance. The statistical analysis included a repeated-measures ANOVA (p < 0.05). Results: the analysis evidenced no significant differences at the end of 6-MRT for all variables (p < 0.05). However, both doses of BA generated a lower post-exertion RPE. The high dose of BA caused significant increases in post-exertion BL (p < 0.05). Conclusion: acute supplementation with BA generated a lower post-exertion RPE. This decrease in RPE and the post-exertion BL increase could be related to an increase in physical performance in HIDZ. (AU)

Introducción: el uso de beta-alanina (BA) para aumentar el rendimiento físico en zonas con dominio de alta intensidad (HIDZ) está ampliamente documentado. Sin embargo, el efecto de este aminoácido sobre el índice de esfuerzo percibido (RPE), la frecuencia cardíaca (HR) y el lactato sanguíneo (BL) aún es incierto. Objetivos: a) determinar el efecto de la suplementación aguda de BA sobre el RPE, la HR y el BL posesfuerzo; y b) además del rendimiento en la prueba de carrera de 6 minutos (6-MRT), en atletas de media distancia. Material y métodos: el estudio incluyó a 12 atletas masculinos de media distancia. El diseño fue cuasiexperimental, intrasujeto, doble ciego y cruzado. Incluyó dos tratamientos (BA en dosis baja [30 mg·kg-1] y BA en dosis alta [45 mg·kg-1]) y placebo, con 72 horas de diferencia. El efecto de BA se evaluó al final de los 6-MRT y posesfuerzo. Las variables fueron RPE, HR y BL, y distancia en 6-MRT (m). El análisis estadístico incluyó un ANOVA de medidas repetidas (p < 0,05). Resultados: el análisis no evidenció diferencias significativas al final de los 6-MRT para todas las variables (p > 0,05). Sin embargo, ambasdosis de BA generaron un menor RPE posesfuerzo. La dosis alta de BA generó incrementos significativos en el BL posesfuerzo (p < 0,05). Conclusión: la suplementación aguda con BA generó un menor RPE posesfuerzo. Esta disminución del RPE y el aumento en el BL posesfuerzo podrían estar relacionados con un aumento del rendimiento físico en HIDZ. (AU)

Effects of acute beta-alanine supplementation on post-exertion rating of per-ceived exertion, heart rate, blood lactate, and physical performance on the 6-minute race test in middle-distance runners.

Introduction: Background: the use of beta-alanine (BA) to increase physical performance in the heavy-intensity domain zone (HIDZ) is widely documented. However, the effect of this amino acid on the post-exertion rating of perceived exertion (RPE), heart rate (HR), and blood lactate (BL) is still uncertain. Objectives: a) to determine the effect of acute BA supplementation on post-exertion RPE, HR, and BL in middle-distance athletes; and b) to determine the effect of acute BA supplementation on physical performance on the 6-minute race test (6-MRT). Material and methods: the study included 12 male middle-distance athletes. The de-sign was quasi-experimental, intrasubject, double-blind & crossover. It had two treat-ments (low-dose BA [30 mg·kg-1] and high-dose BA [45 mg·kg-1]) and a placebo, 72 hours apart. The effect of BA was evaluated at the end of the 6-MRT and post-exertion. The variables were RPE, HR and BL, and 6-MRT (m) distance. The statistical analysis included a repeated-measures ANOVA (p < 0.05). Results: the analysis evidenced no significant differences at the end of 6-MRT for all variables (p ˃ 0.05). However, both doses of BA generated a lower post-exertion RPE. The high dose of BA caused significant increases in post-exertion BL (p ˂ 0.05). Conclusion: acute supplementation with BA generated a lower post-exertion RPE. This decrease in RPE and the post-exertion BL increase could be related to an increase in physical performance in HIDZ.

Introducción: Introducción: el uso de beta-alanina (BA) para aumentar el rendimiento físico en zo-nas con dominio de alta intensidad (HIDZ) está ampliamente documentado. Sin em-bargo, el efecto de este aminoácido sobre el índice de esfuerzo percibido (RPE), la frecuencia cardíaca (HR) y el lactato sanguíneo (BL) aún es incierto. Objetivos: a) determinar el efecto de la suplementación aguda de BA sobre el RPE, la HR y el BL posesfuerzo; y b) además del rendimiento en la prueba de carrera de 6 mi-nutos (6-MRT), en atletas de media distancia. Material y métodos: el estudio incluyó a 12 atletas masculinos de media distancia. El diseño fue cuasiexperimental, intrasujeto, doble ciego y cruzado. Incluyó dos trata-mientos (BA en dosis baja [30 mg·kg-1] y BA en dosis alta [45 mg·kg-1]) y placebo, con 72 horas de diferencia. El efecto de BA se evaluó al final de los 6-MRT y posesfuerzo. Las variables fueron RPE, HR y BL, y distancia en 6-MRT (m). El análisis estadístico in-cluyó un ANOVA de medidas repetidas (p < 0,05). Resultados: el análisis no evidenció diferencias significativas al final de los 6-MRT pa-ra todas las variables (p ˃ 0,05). Sin embargo, ambas dosis de BA generaron un menor RPE posesfuerzo. La dosis alta de BA generó incrementos significativos en el BL poses-fuerzo (p ˂ 0,05). Conclusión: la suplementación aguda con BA generó un menor RPE posesfuerzo. Esta disminución del RPE y el aumento en el BL posesfuerzo podrían estar relacionados con un aumento del rendimiento físico en HIDZ.

Acute Supplementation with Beta-Alanine Improves Performance in Aerobic-Anaerobic Transition Zones in Endurance Athletes.

To determine the acute effect of low and high-dose BA trials on maximal aerobic speed (MAS) in endurance athletes. We hypothesized that high doses of BA have a greater effect than low doses, both compared to baseline.Twelve male endurance athletes volunteered for the study (age = 21.8 ± 2.37 years, weight = 69.8 ± 4.36 kg, height = 174 ± 5.45 cm, maximal oxygen uptake = 59.6 ± 3.77 mLO2·kg-1·min-1). The experimental design applied was randomized cross-over, double-blind. Treatment included three 6-minute run tests (6-MRT), the first as a baseline, then randomized 6-MRT with low (30 mg·kg-1) and high (45 mg·kg-1) dose BA trials. The 6-MRTs were separated by 72 hours. The main variable of the study was the distance (m) performed in the 6-MRT. Differences between tests were established through ANOVA and Tukey's multiple comparison tests (p < 0.05).The analysis showed significant differences between baseline and both doses (p < 0.001). No significant differences were observed between low and high-dose BA trials (p > 0.05).Both 30 and 45 mg·kg-1 of BA increased physical performance at maximal aerobic speed in endurance athletes. The acute intake formats described in the present investigation may be helpful for endurance athletes training and competing in aerobic-anaerobic transition zones.

Relationship between Asymmetries and Functional Autonomy in Older Chilean Adults.

The objectives of this study were: (a) to determine asymmetries, both lower limb (LL) and upper limb (UL), in Chilean older adults, and (b) to relate asymmetries to FA in both LL and UL. Forty-one older adults voluntarily participated in this study (mean ± standard deviation [SD]: age 72.0 ± 8.0 years, LL asymmetries 13.78 ± 14.87%, UL asymmetries 10.70 ± 8.85%, FA 40.35 ± 16.26 points). The variables were: (1) asymmetries of LL and UL, assessed through a force platform and handgrip, respectively; (2) FA, assessed through the Latin American Group for Maturity (GDLAM) and the GDLAM index of autonomy (GI) protocol. The relationship between the variables was performed through Spearman's correlation. The analysis showed that 39% of the participants presented asymmetries above 15% in the LL. Likewise, this 39% of older adults presented a lower FA than their peers with asymmetries below 15% in the LL (≤15%: 35.64 ± 12.26 points vs. >15%: 47.69 ± 19.23 points, p = 0.003). The analysis showed a small correlation between LL and GI asymmetries (r = 0.27, p = 0.07) and a small but negative correlation between UL and GI (r = -0.21). The mean values of asymmetries of both LL and UL are within 'normal' parameters. However, several older adults were identified as being at risk. In parallel, older adults who presented a higher level of asymmetries in LL showed a lower level of FA.

Effects of a period without mandatory physical training on maximum oxygen uptake and anthropometric parameters in naval cadets.

The effects of a period without physical training on the civilian population are well established. However, no studies show the effects of a period without mandatory physical training on maximum oxygen uptake (VO2 max) and anthropometric parameters in naval cadets. This study aimed to investigate changes in VO2 max and anthropometric parameters after 12 weeks without mandatory physical training in naval cadets. The sample was 38 healthy and physically active naval cadets. The measured variables, including VO2 max and anthropometric parameters, were evaluated through the 12-minute race test (12MRT) and the somatotype. Both variables had a separation of 12 weeks without mandatory physical training. A t-test for related samples was used to evidence changes between the test and post-test; effect size was calculated through Cohen's d-test. Distance in 12MRT and VO2 max showed significant decreases at the end of 12 weeks without mandatory physical training (p < 0.001). Likewise, the tricipital skinfold thickness and the endomorphic component showed significant increases (p < 0.05). 12 weeks without mandatory physical training significantly reduces the VO2 max in naval cadets. Simultaneously, the same period without physical training increases both the tricipital skinfold thickness and the endomorphic component in this population.

Fuerza prensil como factor predictor de Ansiedad-Rasgo en estudiantes universitarias / Grip strength as a predictor of Trait-Anxiety in university students

Introducción: Investigaciones han determinado que la implementación de programas de actividad física mejora la salud mental. Sin embargo, aún existen dudas sobre la relación entre fuerza muscular y la presencia de trastornos psicosociales como ansiedad y estrés en la población universitaria. Objetivo: Relacionar la condición física, específicamente la fuerza prensil, con la presencia de Ansiedad-Rasgo en estudiantes mujeres. Materiales y métodos: Investigación empírica con estrategia asociativa predictiva, con un diseño predictivo transversal. La muestra fue de 30 estudiantes mujeres de pregrado. Las variables físicas predictoras evaluadas fueron antropometría, fuerza prensil y consumo máximo de oxígeno, mientras que la Ansiedad-Rasgo se midió por medio del Cuestionario de Ansiedad Estado Rasgo (STAI). Se realizó análisis estadístico con una regresión logística ordinal entre las variables físicas predictoras y nivel de Ansiedad-Rasgo. Resultados: Se evidenció que sólo la fuerza prensil fue estadísticamente significativa (p=0,033). Este análisis expresado en Odds Ratio, asume un 74,36% de probabilidad que a un menor nivel de fuerza prensil, mayor presencia de Ansiedad-Rasgo. Conclusiones: La fuerza prensil, además de ser un parámetro físico que permite detectar riesgo cardiovascular y patologías asociadas, también debería ser considerada en la determinación de alteraciones en salud mental.

Introduction: Research has revealed that the implementation of physical activity programs improves mental health. However, there are still doubts about the relationship between muscle strength and the presence of psychosocial disorders such as anxiety and stress in the university student population. Objective: To study the association of a physical condition (grip strength) and the presence of Trait-Anxiety in female students. Materials and methods: An empirical research with a predictive associative strategy was conducted on a sample of 30 female undergraduate students. The predictor physical variables assessed were anthropometry, grip strength, and maximum oxygen consumption. Trait-Anxiety was evaluated using the State-Trait Anxiety Inventory (STAI). Statistical analysis was performed through ordinal logistic regression between predictor physical variables and level of Trait-Anxiety. Results: Only grip strength was statistically significant (p=0.033). This analysis, expressed as Odds Ratio, assumes a 74.36% probability that the lower level of grip strength, the greater chances of having Trait-Anxiety. Conclusions: Grip strength is not only a physical parameter to detect cardiovascular risks and associated pathologies, but also it should be used to identify mental health disorders.

Validity and reliability of the Muscular Fitness Test to evaluate body strength-resistance

INTRODUCTION: In periods of confinement, people cannot be assessed in training centers. Therefore, it is essential to have valid and reliable tests to evaluate physical capacities remotely and with their respective valuation tables. OBJECTIVE: To determine the validity and reliability of the Muscular Fitness Test (MFT) to evaluate the body strength-resistance with self-loading in healthy young adults. Secondly, to create qualitative scales to evaluate the different levels of this physical capacity. MATERIAL AND METHODS: 489 participants performed the MFT (test), and 77 performed it twice (re-test). The MFT included 60seconds (s) of sit-ups, push-ups, deep squats, and burpees, always in that order, with a micropause of 10s. The validity of the MFT was evaluated with the final heart rate (FHR), % of the reserve HR (%) and Rating of Perceived Exertion (RPE); the reliability included the Coefficient of Variation (CV), Intra-Class Correlation Coefficient (ICC) and the standard error of the mean (SEM) (p < 0.05). The qualitative scales were constructed with the percentiles ≤25: poor, ≤50: fair, ≤75: good, ≤90: very good, and >90: excellent. RESULTS: Participants performed 91.7±26.5 total repetitions, with a FHR of 172.7bpm (81.7%) and RPE of 8.1; CV=2.81%, ICC=0.97 and SEM=0.77 (p < 0.001). CONCLUSION: MFT proved to be valid and reliable to assess self-loaded body strength-resistance in healthy young adults. The creation of the MFT qualitative scales allows evaluating the level of body strength-resistance in this population

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Efecto de la suplementación aguda con bicarbonato sódico sobre el rendimiento en la cancha con obstáculos en pentatletas militares profesionales / Effect of acute sodium bicarbonate supplementation on performance on the obstacle run in professional military pentathlete

INTRODUCCIÓN: La suplementación con bicarbonato sódico (BS) ha sido ampliamente utilizada para retrasar la fatiga en deportes de alta intensidad. Sin embargo, no existe evidencia sobre la suplementación aguda con BS en la prueba de cancha con obstáculos del Pentatlón Militar. OBJETIVO: Determinar el efecto de la suplementación aguda con BS sobre el rendimiento en la cancha con obstáculos en pentatletas militares. MATERIAL Y MÉTODO: Diez pentatletas militares profesionales fueron parte del estudio. El diseño fue de doble ciego, cruzado intrasujeto, mientras que la suplementación fue de 0,3 g·Kg-1 de BS diluida en 500 mL de agua destilada o 0,045 mg·Kg-1 de cloruro de sodio diluido en 500 mL de agua destilada (PL), ambas soluciones fueron ingeridas 60 minutos antes de realizar la prueba de cancha con obstáculos. Las variables fueron: tiempo de ejecución (s) y concentración de lactato ([La]) en los minutos 1, 3, 5, 7 y 9. El análisis estadístico fue realizado a través de una t de Student para muestras independientes, mientras que el tamaño del efecto (ES) fue calculado con la prueba d de Cohen. RESULTADOS: El tiempo en la cancha con obstáculos evidenció un descenso significativo luego de la suplementación con BS (p < 0,01; ES = 0,48; Δ = 3,7%), mientras que las [La] mostraron diferencias significativas entre ambos grupos en los minutos 5, 7 y 9 (p < 0,05). CONCLUSIONES: Al término del estudio, se comprobó que la suplementación aguda con BS aumentó el rendimiento en la prueba de cancha con obstáculos. Por lo tanto, la ingesta aguda con BS podría ser considerada como una ayuda ergogénica por los pentatletas militares

INTRODUCTION: Sodium bicarbonate (SB) supplementation has been widely used to delay fatigue in high intensity sports. However, there is no evidence on acute supplementation with SB in the obstacle run in Military Pentathlon. OBJECTIVE: To determine the effect of acute supplementation with SB on performance on the obstacle run in military pentathletes. MATERIAL AND METHOD: Ten professional military pentathletes were part of the study. The design was double blind, cross-over intra-subject, while supplementation was 0.3 g·Kg-1 SB diluted in 500 mL of distilled water or 0.045 mg·Kg-1 of sodium chloride diluted in 500 mL of distilled water (PL), both solutions ingested 60 minutes before performing the obstacle run. The variables were: execution time (s) and lactate concentration ([La]) in minutes 1, 3, 5, 7 and 9. The statistical analysis was performed through a Student's t test for independent samples, while the effect size (ES) was calculated with the Cohen d test. RESULTS: The time in the obstacle run showed a significant decrease after the SB supplementation (p <0.01, ES = 0.48, Δ = 3.7%), while the [La] showed significant differences between both groups in the 5, 7, and 9 minutes (p < 0.05). CONCLUSIONS: At the end of the study, it was found that acute supplementation with SB increased performance in the obstacle run. Therefore, acute SB ingestion could be considered as an ergogenic aid by military pentathletes

Efectos de un programa de Zumba(R) sobre niveles de ansiedad-rasgo, ansiedad-estado y condición física en estudiantes universitarias chilenas / Effects of a Zumba(R) program over levels of anxiety-trait, anxiety-state and physical condition in Chilean university students / Efeito de um programa Zumba(R) nos níveis de ansiedade-traço, ansiedade-estado e condição física em estudantes universitários chilenos

Diversas investigaciones han determinado que la implementación de programas de actividad física mejora la salud mental. Sin embargo, aún existen dudas sobre los beneficios de los programas Zumba® en la población que lo practica. El propósito de este estudio fue determinar los efectos de un programa de ejercicio físico basado en Zumba®, sobre los niveles de ansiedad-rasgo y ansiedad-estado en estudiantes universitarias chilenas. Investigación cuantitativa cuasi-experimental, con una muestra de 22 estudiantes mujeres de pregrado (grupo experimental = 10 y grupo control = 12). Las variables fueron: ansiedad-rasgo (A-R) y ansiedad-estado (A-E), además de variables físicas como antropometría, consumo máximo de oxígeno (VO2máx) y fuerza prensil. El análisis estadístico se realizó a través de un ANOVA mixto para todas las variables. En nivel de significancia fue de p < 0,05. Los resultados evidenciaron cambios no significativos en los distintos niveles de A-R ni A-E luego de la aplicación del programa de Zumba® (p > 0,05), tampoco hubo cambios en las otras variables de estudio (p > 0,05). Al término de la intervención, no se observaron efectos del programa de Zumba® sobre los distintos niveles de A-R y A-E, como tampoco sobre variables antropométricas, VO2máx ni fuerza prensil

Several investigations have specified that the implementation of physical activity programs improve mental health. However, there are still doubts about the benefits on the population taking part in Zumba® programs. The purpose of this study was to determine the effects of a Zumba® based working out program on the levels of anxiety-trait and anxiety-state in Chilean university students. It was a quantitative, cuasi-experimental study with a sample of 22 undergraduate female students (experimental group = 10 and control group = 12). The variables were anxiety-trait (A-T) and anxiety-state (A-S), in addition to physical variables, such as anthropometry, maximum oxygen consumption (VO2max) and grip strength. A statistical analysis was performed through a mixed ANOVA. The level of significance for all analyses was p < 0.05. The results showed no significant changes in the different levels of A-T or A-S (p > 0.05), there were also no changes in the other variables (p > 0.05). At the end of the intervention, no effects of the Zumba® program were observed on the different levels of A-T and A-S, nor on anthropometric variables, VO2max or grip strength

Várias investigações determinaram que a implementação de programas de atividade física melhora a saúde mental. No entanto, ainda existem dúvidas sobre os benefícios dos programas Zumba® na população que pratica. O objetivo deste estudo foi determinar os efeitos de um programa de exercícios físicos baseado no Zumba®, sobre níveis de Ansiedade-Traço e Ansiedade-Estado em estudantes universitários chilenos. Pesquisa quantitativa quase experimental, com uma amostra de 22 estudantes do sexo feminino (grupo experimental [GE] = 10 e grupo controle [GC] = 12). As variáveis foram: Ansiedade-Traço (A-T) e Ansiedade-Estado (A-E), ambas avaliadas pelo STAI Trait State Anxiety Questionnaire, além de variáveis físicas como antropometria, consumo máximo de oxigênio (VO2máx) e força pré-trilateral. A análise estatística foi realizada através de uma ANOVA mista para todas as variáveis e uma tabela de contingência por meio do Qui-Quadrado de Pearson para os diferentes níveis de A-T e A-E. O nível de significância para todas as análises foi de p <0,05. Os resultados não mostraram alterações significativas em todas as variáveis do estudo após a aplicação do programa Zumba® (p> 0,05); também não houve diferenças nos diferentes níveis de A-T ou A-E (p> 0,05). Ao final da intervenção, não foram observados efeitos do programa Zumba® sobre diferentes níveis de A-R e A-E, nem nas variáveis antropométricas, VO2máx ou força preênsil

Efectos de la suplementación aguda con beta-alanina sobre una prueba de tiempo límite a velocidad aeróbica máxima en atletas de resistencia / Effects of acute supplementation with beta-alanine on a limited time test at maximum aerobic speed on endurance athletes

Introducción: la beta-alanina (BA) es una de las ayudas ergogénicas más utilizadas actualmente por deportistas, pero la mayoría de los estudios centran su investigación en la suplementación prolongada. Objetivos: determinar el efecto agudo de la suplementación con BA sobre una prueba de tiempo límite (PTL) a velocidad aeróbica máxima (VAM) en atletas de resistencia. Material y método: once atletas de resistencia (VO2máx 61,6 ± 9,5 mLO2·kg-1·min-1) fueron parte del estudio. El diseño fue doble ciego, cruzado intrasujeto, y la suplementación de BA fue de 30 mg·kg-1 o placebo (PL) 60 minutos antes de completar una PTL. Las variables fueron: tiempo y distancia en la PTL y concentraciones de lactato ([La]) postesfuerzo en los minutos 1, 3, 5, 7 y 9. Para el análisis se utilizó una prueba t de Student y el tamaño del efecto (TE) se realizó mediante la prueba d de Cohen. Resultados: el tiempo en la PTL evidenció diferencias significativas entre la BA y PL (p = 0,047; TE = 0,48). No se observaron diferencias significativas en distancia entre ambos grupos (p = 0,071; TE = 0,48) y las [La] evidenciaron diferencias significativas entre ambos grupos en los minutos 3, 5 y 7, respectivamente (p < 0,05). Conclusión: la suplementación aguda con BA evidenció aumentos significativos en el tiempo de ejecución en la PTL a intensidades correspondientes a VAM. Por lo anterior, la suplementación aguda con BA es una ayuda ergogénica que podría ser considerada por los atletas de resistencia para aumentar el rendimiento deportivo

Introduction: the beta-alanine (BA) is one of the ergogenic aid most used by athletes, but the majority of the studies center the research on chronic supplementation. Objectives: to determine the acute effect of BA supplementation on a limited time test (LTT) at maximum aerobic speed (MAS) on endurance athletes. Material and method: eleven endurance athletes (VO2max 61.6 ± 9.5 mLO2·kg-1·min-1) were part of the study. The study consisted of a double-blind, cross-over intra-subject design, and the BA supplementation was 30 mg·kg-1 or placebo (PL) 60 minutes before completing a LTT. The variables were: time and distance in LTT, and post-effort lactate concentrations ([La]) in minutes 1, 3, 5, 7, and 9. The Student's t test was used for the analysis and the size of the effect (SE) was measured through Cohen's d test. Results: the time on LTT showed significant differences between BA and PL (p = 0.047; SE = 0.48). No significant differences were seen between both groups (p = 0.071; SE = 0.48), and [La] showed significant differences between both groups in minutes 3, 5 and 7, respectively (p < 0.05). Conclusion: acute supplementation with BA showed a significant increase in the execution time in LTT in the intensities connected to MAS. Hence, acute supplementation with BA is an ergogenic aid that could be considered by resistance athletes in order to increase the athletic performance

[Effects of acute supplementation with beta-alanine on a limited time test at maximum aerobic speed on endurance athletes]. / Efectos de la suplementación aguda con beta-alanina sobre una prueba de tiempo límite a velocidad aeróbica máxima en atletas de resistencia.

INTRODUCTION: Introduction: the beta-alanine (BA) is one of the ergogenic aid most used by athletes, but the majority of the studies center the research on chronic supplementation. Objectives: to determine the acute effect of BA supplementation on a limited time test (LTT) at maximum aerobic speed (MAS) on endurance athletes. Material and method: eleven endurance athletes (VO2max 61.6 ± 9.5 mLO2•kg-1•min-1) were part of the study. The study consisted of a double-blind, cross-over intra-subject design, and the BA supplementation was 30 mg•kg-1 or placebo (PL) 60 minutes before completing a LTT. The variables were: time and distance in LTT, and post-effort lactate concentrations ([La]) in minutes 1, 3, 5, 7, and 9. The Student's t test was used for the analysis and the size of the effect (SE) was measured through Cohen's d test. Results: the time on LTT showed significant differences between BA and PL (p = 0.047; SE = 0.48). No significant differences were seen between both groups (p = 0.071; SE = 0.48), and [La] showed significant differences between both groups in minutes 3, 5 and 7, respectively (p < 0.05). Conclusion: acute supplementation with BA showed a significant increase in the execution time in LTT in the intensities connected to MAS. Hence, acute supplementation with BA is an ergogenic aid that could be considered by resistance athletes in order to increase the athletic performance.

INTRODUCCIÓN: Introducción: la beta-alanina (BA) es una de las ayudas ergogénicas más utilizadas actualmente por deportistas, pero la mayoría de los estudios centran su investigación en la suplementación prolongada. Objetivos: determinar el efecto agudo de la suplementación con BA sobre una prueba de tiempo límite (PTL) a velocidad aeróbica máxima (VAM) en atletas de resistencia. Material y método: once atletas de resistencia (VO2máx 61,6 ± 9,5 mLO2•kg-1•min-1) fueron parte del estudio. El diseño fue doble ciego, cruzado intrasujeto, y la suplementación de BA fue de 30 mg•kg-1 o placebo (PL) 60 minutos antes de completar una PTL. Las variables fueron: tiempo y distancia en la PTL y concentraciones de lactato ([La]) postesfuerzo en los minutos 1, 3, 5, 7 y 9. Para el análisis se utilizó una prueba t de Student y el tamaño del efecto (TE) se realizó mediante la prueba d de Cohen. Resultados: el tiempo en la PTL evidenció diferencias significativas entre la BA y PL (p = 0,047; TE = 0,48). No se observaron diferencias significativas en distancia entre ambos grupos (p = 0,071; TE = 0,48) y las [La] evidenciaron diferencias significativas entre ambos grupos en los minutos 3, 5 y 7, respectivamente (p < 0,05). Conclusión: la suplementación aguda con BA evidenció aumentos significativos en el tiempo de ejecución en la PTL a intensidades correspondientes a VAM. Por lo anterior, la suplementación aguda con BA es una ayuda ergogénica que podría ser considerada por los atletas de resistencia para aumentar el rendimiento deportivo.

Acute effect of an Intra-Set Variable Resistance of back squats over 30-m sprint times of female sprinters / Efecto agudo de un protocolo de resistencia variable intra-serie en sentadillas sobre el tiempo en 30 metros lisos en mujeres velocistas

Introduction: Several pre-conditioning methods have been tested in order to produce Postactivation Potentiation (PAP) in men. However, it is unknown if Intra-Set Variable Resistance generates the same effect in female sprinters. Objective: Thus, the acute effect of an Intra-Set Variable Resistance (I-SVR) protocol of back squats on 30-m sprint times of female sprinters was determined. Material and method: Ten female sprinters were the subjects of this study (age = 20.3 ± 1.9 years, body mass 56.0 ± 6.9 kg, height = 1.64 ± 6.1 m, 30-m sprint = 4609.2 ± 236.4 ms). The pre-conditioning with I-SVR consisted of 4 back squats exercise sets: each set included 22% 1RM X 5 reps (equivalent to 1.0-1.1 · s-1), 60% 1RM X 4 reps (equivalent to 0.6-0.7 · s-1), and 30-m sprint X 3 with a 2-minute rest. Results: The repeated measures ANOVA did not show significant differences in 30-m sprint after the application of pre-conditioning protocols with I-SVR (p > 0.05), while [La] provided evidence of a significant increase post-effort (p < 0.0001). However, great individual variations were observed. Conclusions: Considering that the pre-conditioning with I-SVR did not increase the performance in women sprinters, which may be due to insufficient load to elicit a PAP response or that the fatigue induced outweighs the benefit, the coaches con-sidering the use of this pre-conditioning protocol in order to generate PAP must explore its effectiveness individually. Factors such as strength levels, protocol resistance used to generate PAP, and, above all, the recovery interval between pre-conditioning and the following sprint need further research

Introducción: Varios métodos de pre-activación se han probado para desencadenar Potenciación Post Activación (PAP) en hombres. Sin embargo, se desconoce si la Resistencia Variable Intra-Serie genera el mismo efecto en mujeres velocistas. Objetivo: Determinar el efecto agudo de un protocolo de Resistencia Variable Intra-Serie (RVI-S) en sentadillas sobre el tiempo en 30 metros lisos en mujeres velocistas. Material y método: Diez velocistas de nivel regional fueron parte de este estudio (edad = 20,3 ± 1,9 años, masa corporal 56,0 ± 6,9 kg, estatura = 1,64 ± 6,1 m, 30 metros lisos = 4609,2 ± 236,4 ms). La pre-activación con RVI-S consistió en 4 series de sentadillas: cada serie incluyó 5 repeticiones al 22% de 1RM (equivalente a 1,0-1,1 · s-1) + 4 repeticiones al 60% de 1RM (equivalente a 0,6-0,7 · s-1) + 3 carreras de 30 metros separadas con una pausa de 2 minutos. Las variables fueron: el tiempo promedio de tres repeticiones de 30 metros de carrera y concentraciones de Lactacto ([La]). Resultados: La ANOVA de medias repetidas no mostró diferencias significativas en el tiempo promedio realizado en 30 metros lisos después de la aplicación de protocolos de pre-activación con RVI-S (p > 0,05), mientras que las [La] mostraron incrementos significativos post esfuerzo (p < 0,0001). Sin embargo, se observaron grandes variaciones individuales. Conclusiones: Considerando que la pre-activación con RVI-S no mostró incrementos en el rendimiento en mujeres velocistas, posiblemente por una carga insuficiente para desencadenar PAP o que la fatiga muscular superó el posible beneficio, los entrenadores que consideren el uso de este protocolo de pre-activación para genera PAP deben explorar la efectividad en forma individual. Factores tales como los niveles de fuerza, la resistencia del protocolo usado para generar PAP, y por sobre todo el intervalo de recuperación entre la pre-activación y la subsiguiente carrera necesitan de mayor investigación

Time to fatigue on lactate threshold and supplementation with sodium bicarbonate in middle-distance college athletes / Tiempo hasta la fatiga sobre el umbral láctico y suplementación con bicarbonato de sodio en corredores de medio fondo universitarios

Introduction: There have been many researches that have attempted to improve sports performance based on supplementation with different buffer substances. Within this group of substances, sodium bicarbonate supplementation has been widely used in both cyclic and acyclic sports. In the case of cyclic sports, it has been tried to improve the performance of pedestrian races at different percentages of peak oxygen uptake. However, the results on intensity over anaerobic threshold have been contradictory. Objective: To determine the performance variation based on execution in a endurance test after sodium bicarbonate administration. The second aim to evaluate the levels of blood lactate in the finish of endurance test. Material and method: Five college athletes of middle-endurance and endurance race runners were subjects in the study. The variables measured were: effort maximum time (in seconds) measured through a endurance test, and maximum lactate post effort. All athletes were administered sodium bicarbonate (0.3 g·Kg-1 body mass) or a placebo (0.045 g·Kg-1 body mass) an hour before each endurance test. Student’s t-test (lactate) and Wilcoxon (time) was used for the statistical analysis. The size of the effect was calculated with Cohen’s d-test. Results: The effort maximum time showed a significant increase (P < 0.042; size of the effect = 0.852) as well as lactate concentrations post effort (P < 0.022; size of the effect = 1.987). Conclusions: The results of the study showed that the supplementation whit sodium bicarbonate generates an increase in the performance and lactate concentrations post effort, when the race speed surpass by seven percent the anaerobic threshold speed

Introducción: Han sido muchas las investigaciones que han intentado mejorar el rendimiento deportivo en base a la suplementación con diferentes sustancias buffer. Dentro de este grupo de sustancias, la suplementación con bicarbonato de sodio ha sido ampliamente utilizada tanto en deportes cíclicos como acíclicos. En el caso de deportes cíclicos, se ha experimentado mejorar el rendimiento de carreras pedestres a diferentes porcentajes del consumo máximo de oxigeno. Sin embargo, los resultados a intensidades por sobre el umbral láctico han sido contradictorios. Objetivo: Determinar la variación del rendimiento en base al tiempo de ejecución y producción de lactato post esfuerzo en una prueba de resistencia a una intensidad por sobre el UL posterior a la suplementación con bicarbonato de sodio. Material y métodos: Cinco atletas de medio fondo y fondo universitarios fueron parte del estudio. Las variables medidas fueron: tiempo máximo de esfuerzo (segundos) evaluado a través de una prueba de tiempo límite y lactato máximo post esfuerzo. Una hora antes de cada prueba de tiempo límite los atletas fueron suplementados con bicarbonato de sodio (0,3 g·Kg-1 masa corporal) o un placebo (0,045 g·Kg-1 masa corporal). Para el análisis estadístico se utilizó la prueba t de Student (lactato) y Wilcoxon (tiempo). El tamaño del efecto fue calculado con la prueba d de Cohen. Resultados: El tiempo máximo de esfuerzo tuvo incrementos significativos (p < 0,042; tamaño del efecto = 0,852), al igual que las concentraciones de lactato post esfuerzo (p < 0,022; tamaño del efecto = 1,987). Conclusión: Los resultados del estudio mostraron que la suplementación con bicarbonato de sodio genera un aumento en el rendimiento y en las concentraciones de lactato post esfuerzo, cuando la velocidad de desplazamiento sobrepasa un siete por ciento la velocidad de umbral láctico

[Effects of a high intensity interval training on the aerobic capacity of adolescents]. / Efectos de un entrenamiento intervalado de alta intensidad en la capacidad aeróbica de adolescentes.

BACKGROUND: If aerobic capacity is stimulated early in life, maximal oxygen consumption during adulthood is assured. AIM: To analyze the effects of a high intensity interval training (HIIT) in adolescents on the maximal oxygen consumption (VO2max) measured using the 20-m shuttle run test (20mSRT). MATERIAL AND METHODS: Twenty eight teenagers aged 13 ± 0.6 years were divided in two groups of 14 subjects each. One group was to a 16 sessions of HIIT interval training based on their individual maximal aerobic speed and the other continued with their usual exercise done at school. At baseline and the end of the intervention VO2max was measured using the 20mSTR. RESULTS: At the end of the intervention, the trained teenagers significantly improved their VO2max and the time spent in the 20mSTR. CONCLUSIONS: A HIIT program based on the individual maximal aerobic speed improves VO2max in adolescents.

Efecto de un método de Entrenamiento Intervalado de Alta Intensidad sobre el consumo máximo de oxígeno en escolares chilenos / Effect of a High-intensity Interval Training method on maximum oxygen consumption in Chilean schoolchildren

Resumen Introducción: Los bajos niveles de Consumo Máximo de Oxígeno (VO2max) evaluados en escolares chilenos, sugieren la puesta en marcha de entrenamientos que mejoren la capacidad aeróbica. Objetivo: Analizar el efecto de un método de Entrenamiento Intervalado de Alta Intensidad sobre el Consumo Máximo de Oxígeno en escolares chilenos. Materiales y métodos: Treinta y dos escolares de octavo año básico divididos en dos grupos fueron parte del estudio (grupo experimental = 16 y grupo control = 16). La principal variable analizada fue el Consumo Máximo de Oxígeno a través del Test de Course Navette. Se aplicó un método de Entrenamiento Intervalado de Alta Intensidad basado en la Velocidad Aeróbica Máxima obtenida a través del Test. Para el análisis estadístico se utilizó un ANOVA Mixto. Resultados: El grupo experimental presentó un aumento significativo en el Consumo Máximo de Oxígeno entre el pre test y post test al ser comparado con el grupo control (p < 0.0001). Conclusión: Los resultados del estudio mostraron un efecto positivo del Entrenamiento Intervalado de Alta Intensidad sobre el Consumo Máximo de Oxígeno. Al término del estudio, se concluye que el Entrenamiento Intervalado de Alta Intensidad es una buena metodología de estimulación para escolares chilenos.

Abstract Introduction: The low levels of maximum oxygen consumption (VO2max) evaluated in Chilean schoolchildren suggest the startup of trainings that improve the aerobic capacity. Objective: To analyze the effect of a High-intensity Interval Training method on maximum oxygen consumption in Chilean schoolchildren. Materials and methods: Thirty-two high school students from the eighth grade, who were divided into two groups, were part of the study (experimental group = 16 students and control group = 16 students). The main analyzed variable was the maximum oxygen consumption through the Course Navette Test. A High-intensity Interval training method was applied based on the maximum aerobic speed obtained through the Test. A mixed ANOVA was used for statistical analysis. Results: The experimental group showed a significant increase in the Maximum Oxygen Consumption between the pretest and posttest when compared with the control group (p < 0.0001). Conclusion: The results of the study showed a positive effect of the High-intensity Interval Training on the maximum consumption of oxygen. At the end of the study, it is concluded that High-intensity Interval Training is a good stimulation methodology for Chilean schoolchildren.

Influence of intermittent aerobic performance on the variables of static and dynamic apnea performances / Influencia del rendimiento aeróbico intermitente sobre las variables de rendimiento de la apnea estática y dinámica

Over the last years, sport diving has become one of the most studied physical activities. Several physiological responses have been described and analyzed during immersions of static, dynamic, and deep apnea sessions. These analyses, and several others, have been focused mainly on the cardiovascular and hemodynamic changes that this activity produces. Objective: To determine the influence of aerobic performance of static and dynamic apnea before and after an out-water training based on the average velocity of a 12-minute test. Material and Method: Eight apnea scuba divers of the Chilean Navy were part of this study. The variables measured were: aerobic performance measured through a 12-minute test, static and dynamic apnea. The protocol used for the aerobic performance development was a study based on the average velocity of a 12-minute test. The statistical analysis was performed with Student's t-test and the size of the effect with Cohen's d test. Results: The aerobic performance showed a significant increase between the pre and post-test (p < 0.001; size of the effect = 1.263). The static apnea did not show significant modifications (p > 0.05; size of the effect = 0.025). Lastly, the dynamic apnea showed a significant increase in both measurements (p < 0.05; size of the effect = 0.404). Conclusions: The result of the study showed that increasing the aerobic performance generates a rise in the distance of dynamic apnea. For that reason, it is suggested that apnea scuba divers perform out-water trainings based on the average velocity of 12-minute test as a complement to their immersion training

En los últimos años, el buceo deportivo se ha convertido en una de las actividades físicas más estudiadas. Dentro de estas investigaciones, se han descrito y analizado las respuestas fisiológicas corporales durante las inmersiones de apnea estática y dinámica. De forma específica, los análisis se han centrado principalmente en los cambios cardiovasculares y hemodinámicos que esta actividad deportiva produce. Objetivo: Determinar la influencia del rendimiento aeróbico en la apnea estática y dinámica antes y después de un entrenamiento fuera del agua basado en la velocidad promedio obtenida a través del test de 12 minutos. Material y Método: Ocho buceadores de apnea perteneciente a la Escuela Naval de la Armada de Chile fueron parte del estudio. Las variables medidas fueron: rendimiento aeróbico a través del test de 12 minutos, apnea estática y dinámica. El protocolo usado para el desarrollo del rendimiento aeróbico fue basado en la velocidad promedio del test de 12 minutos. El análisis estadístico fue realizado a través de una t de Student y el tamaño del efecto con una d de Cohen. Resultados: El rendimiento aeróbico mostró incrementos significativos entre el pre test y el post test (p < 0,001; tamaño del efecto = 1,263). La apnea estática no mostró cambios significativos (p > 0,05; tamaño del efecto = 0,025). Finalmente, la apnea dinámica mostró incrementos significativos entre ambas mediciones (p < 0,05; tamaño del efecto = 0,404). Conclusiones: El resultado del estudio mostró que un incremento en el rendimiento aeróbico genera un aumento en la distancia alcanzada en apnea dinámica. Por tal razón, se sugiere que los buceadores de apnea realicen entrenamientos fuera del agua. Por último, los entrenamientos pedestres basados en la velocidad promedio de la prueba de 12 minutos, son un buen complemento del entrenamiento de inmersión

Efectos y alteraciones cardiovasculares provocados por la práctica de deportes de resistencia. Una revisión sistemática / Cardiovascular effects and alterations from endurance sports. A systematic review

La práctica de actividad física, especialmente el deporte de resistencia, produce adaptaciones cardiovasculares beneficiosas para la salud. Sin embargo, en varias investigaciones se ha reportado la presencia de algún tipo de arritmias cardíacas ventriculares o supraventriculares, lo que ha desencadenado una alerta en los profesionales que recomiendan este tipo de estímulos. Consecuencia de lo anterior, fue imprescindible revisar y analizar la evidencia científica existente dentro de los últimos 10 años sobre las posibles arritmias y alteraciones cardiovasculares que generan los deportes de resistencia. En la siguiente revisión sistemática se evaluaron publicaciones entre los años 2006 y 2016 que relacionaron los deportes de resistencia con arritmias cardiacas. Se identificaron 12 artículos, que fueron agrupados según el efecto generado en el corazón (arritmias, fibrilación auricular, fibrosis cardíaca y cambios anatómicos). Debido a la alta exigencia cardíaca a que se exponen los deportistas de resistencia, existe una tendencia a la aparición de distintos tipos de arritmias (AU)

The practice of endurance sports provides health benefits due to cardiovascular adaptation. Nevertheless, there has been a lot of research in which patients have shown some type of ventricular cardiac arrhythmia. This has worried some professionals who have been utilizing this kind of training. As a result of this, professionals have begun revising and analyzing The scientific evidence from the last ten years. This investigation was focused on the review of possible development of arrhythmias and cardiovascular alterations that endurance sports can cause. In the following systematic review, we evaluate publications that show a direct relation between endurance sports and cardiac arrhythmias from 2006 to 2016. Twelve articles were identified and then grouped by different effects on the heart. Due to the high levels of cardiac stressthat endurance-trained athletes are exposed to, there is a tendency for them to show different types of arrhythmias (AU)

Efectos de un entrenamiento intervalado de alta intensidad en la capacidad aeróbica de adolescentes / Effects of a high intensity interval training on the aerobic capacity of adolescents

Background: If aerobic capacity is stimulated early in life, maximal oxygen consumption during adulthood is assured. Aim: To analyze the effects of a high intensity interval training (HIIT) in adolescents on the maximal oxygen consumption (VO2max) measured using the 20-m shuttle run test (20mSRT). Material and Methods: Twenty eight teenagers aged 13 ± 0.6 years were divided in two groups of 14 subjects each. One group was to a 16 sessions of HIIT interval training based on their individual maximal aerobic speed and the other continued with their usual exercise done at school. At baseline and the end of the intervention VO2max was measured using the 20mSTR. Results: At the end of the intervention, the trained teenagers significantly improved their VO2max and the time spent in the 20mSTR. Conclusions: A HIIT program based on the individual maximal aerobic speed improves VO2max in adolescents.