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.

Does Co-Supplementation with Beetroot Juice and Other Nutritional Supplements Positively Impact Sports Performance?: A Systematic Review.

In the pursuit of enhanced athletic prowess in different disciplines, athletes constantly look for strategies to increase their physical performance, encompassing technical skills and dietary components, which inevitably, in most cases, include the incorporation of sports supplements. In recent years, there has been an increase in the number of athletes using ergogenic aids. In this context, scientific evidence must play a prominent role in either endorsing or warning against the use of these products, ensuring the preservation of health while promoting the theoretically established positive benefits. In this vein, beetroot juice (BJ) stands out as a key supplement as an ergogenic aid to improve sports performance, given its demonstrated influence on both aerobic and anaerobic exercise. However, despite widespread global demand, there remains a lack of understanding regarding the potential synergistic effects of combining BJ with other supplements. Consequently, our study aims to determine whether the combination of BJ with another nutritional supplement can enhance its beneficial effects and, therefore, optimize physical performance in humans. A comprehensive literature search was conducted in two major databases-Web of Science and PubMed-from 1 January 2018 to 29 January 2023, using specific keywords. After the exclusion criteria, six articles were selected for analysis. Therefore, our study shows that the effectiveness of combining BJ with another supplement mainly depends on the duration of the chronic intervention, which is where the greatest benefits have been observed.

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)

Plant-Based Nutrition: Exploring Health Benefits for Atherosclerosis, Chronic Diseases, and Metabolic Syndrome-A Comprehensive Review.

Atherosclerosis, chronic non-communicable diseases, and metabolic syndrome are highly interconnected and collectively contribute to global health concerns that reduce life expectancy and quality of life. These conditions arise from multiple risk factors, including inflammation, insulin resistance, impaired blood lipid profile, endothelial dysfunction, and increased cardiovascular risk. Adopting a plant-based diet has gained popularity as a viable alternative to promote health and mitigate the incidence of, and risk factors associated with, these three health conditions. Understanding the potential benefits of a plant-based diet for human health is crucial, particularly in the face of the rising prevalence of chronic diseases like diabetes, hypertension, dyslipidemia, atherosclerosis, and cancer. Thus, this review focused on the plausible advantages of consuming a type of food pattern for the prevention and/or treatment of chronic diseases, emphasizing the dietary aspects that contribute to these conditions and the evidence supporting the benefits of a plant-based diet for human health. To facilitate a more in-depth analysis, we present separate evidence for each of these three concepts, acknowledging their intrinsic connection while providing a specific focus on each one. This review underscores the potential of a plant-based diet to target the underlying causes of these chronic diseases and enhance health outcomes for individuals and populations.

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.

Effect of Intensity and Duration of Exercise on Gut Microbiota in Humans: A Systematic Review.

(1) Background: The gut microbiota might play a part in affecting athletic performance and is of considerable importance to athletes. The aim of this study was to search the recent knowledge of the protagonist played by high-intensity and high-duration aerobic exercise on gut microbiota composition in athletes and how these effects could provide disadvantages in sports performance. (2) Methods: This systematic review follows the PRISMA guidelines. An exhaustive bibliographic search in Web of Science, PubMed, and Scopus was conducted considering the articles published in the last 5 years. The selected articles were categorized according to the type of study. The risk of bias was assessed using the Joanna Briggs Institute's Critical Appraisal Tool for Systematic Reviews. (3) Results: Thirteen studies had negative effects of aerobic exercise on intestinal microbiota such as an upsurge in I-FABP, intestinal distress, and changes in the gut microbiota, such as an increase in Prevotella, intestinal permeability and zonulin. In contrast, seven studies observed positive effects of endurance exercise, including an increase in the level of bacteria such as increased microbial diversity and increased intestinal metabolites. (4) Conclusions: A large part of the studies found reported adverse effects on the intestinal microbiota when performing endurance exercises. In studies carried out on athletes, more negative effects on the microbiota were found than in those carried out on non-athletic subjects.

Efectos de una intervención nutricional asociada a entrenamiento concurrente en la composición corporal de hombres físicamente activos / Effects of a nutritional intervention associated with concurrent training on the body composition of physically active men

RESUMEN: La práctica regular de ejercicio físico es una de las estrategias que se utiliza para optimizar la composición corporal. Para esto, no siempre se considera una intervención nutricional como parte de un trabajo interdisciplinario. El objetivo de este estudio fue identificar los efectos de un programa de intervención nutricional asociada a un entrenamiento concurrente en la composición corporal evaluada a través de bioimpedancia eléctrica (BIA) en hombres físicamente activos. La intervención tuvo una duración de 6 meses, donde participaron 12 personas (23,4 ± 4,9 años). Durante los primeros 5 meses se aplicó una planificación alimentaria y de entrenamiento ajustado a las características individuales de cada uno de los participantes, al comienzo del 6º mes, fue eliminada la planificación alimentaria y sólo se mantuvo el entrenamiento, esto con el objetivo de analizar los posibles cambios de composición corporal de los participantes. Antes (previo al programa de intervención), durante (al final del mes 5) y posterior a la intervención (final del mes 6) se evaluó el tejido adiposo, muscular y la masa libre de grasa a través de bioimpedancia eléctrica (BIA). Los resultados muestran que el programa de entrenamiento con intervención nutricional generaron en los primeros 5 meses, una disminución del porcentaje de tejido adiposo (PRE= 16,20 ± 4,75; POST= 9,52 ± 3,70; p= 0,000; TE= 1,51) e índice de tejido adiposo (PRE= 5,34 ± 1,75; POST= 3,16 ± 1,34; p=0,001; TE=1,35), aumento del porcentaje de tejido muscular (PRE= 46,05 ± 3,02; POST= 49,90 ± 2,90; p=0,004; TE= -1,25) y aumento el índice muscular/adiposo (PRE= 2,53 ± 0,75; POST= 4,85 ± 2,64; p=0,005; TE= -1,15), efectos que se atenúan significativamente cuando la intervención nutricional fue retirada del programa de intervención (p>0.05). Se concluye que la intervención nutricional es un factor clave para generar efectos positivos en la optimización de la composición corporal independientemente del nivel de entrenamiento de las personas. Estos resultados evidencian la importancia de la realización de una planificación alimentaria individualizada, ejecutada por un profesional nutricionista en los cambios de la composición corporal en sujetos físicamente activos. Los resultados de este estudio podrían orientar la consideración de un profesional nutricionista a la hora de formar equipos transdisciplinarios con el fin de mejorar hábitos de alimentación y de composición corporal.

SUMMARY: The regular practice of a certain type of training is one of the strategies used to optimize body composition. Consequently, nutritional intervention is not always considered as part of interdisciplinary work. This study aimed to identify the effects of a nutritional intervention program associated with concurrent training on body composition, assessed through bioelectrical impedance (BIA) in physically active men. The intervention lasted 6 months, with the participation of 12 subjects (23.4 ± 4.9 years). During the first 5 months, food and training planning was applied, adjusted to the individual characteristics of each of the participants. At the beginning of the 6th month, food planning was eliminated and only training was maintained, to analyze the possible changes in body composition of the participants. Prior to (before the intervention program), during (at the end of month 5), and after the intervention (end of month 6), adipose tissue, muscle, and fat-free mass were evaluated through electrical bioimpedance (BIA). The results showed that in the first five months, this training program generated a decrease in the percentage of adipose tissue (PRE= 16.20 ± 4.75; POST= 9.52 ± 3.70; p= 0.000; ES= 1.51) and adipose tissue index (PRE= 5.34 ± 1.75; POST= 3.16 ± 1.34; p=0.001; ES=1.35), increase in the percentage of muscle tissue (PRE= 46.05 ± 3.02; POST= 49.90 ± 2.90; p=0.004; ES= -1.25) and increased muscle/fat index (PRE= 2.53 ± 0.75; POST = 4.85 ± 2.64, p=0.005, SE= -1.15). The above effects were significantly reduced when the nutritional intervention was withdrawn from the program (p>0.05). It is concluded that nutritional intervention is a key factor to generate positive effects in the optimization of body composition regardless of the level of training. These results show the importance of individualized food planning, carried out by a professional nutritionist with regard to changes in the body composition of physically active subjects. The results of this study could be useful for nutritionists when forming disciplinary teams to improve eating habits and body composition.

Sleep Quality in Chilean Professional Soccer Players.

Recent research has shown that good sleep quality has a positive effect on physical performance. However, sleep quality in Chilean professional soccer players is unknown. The purpose of this study was to determine sleep quality in Chilean professional soccer players. It was a cross-sectional, explanatory study with observable variables. The sample consisted of 94 Chilean male soccer players belonging to four professional clubs. The main variable was the Sleep Quality Index, evaluated through the Pittsburgh questionnaire (Spanish version). After estimating sleep quality individually, the four professional soccer clubs' comparison was performed through a one-factor ANOVA. The Pearson test was used to relate the questionnaire variables; the significance level was p < 0.05. In the global analysis of the Pittsburgh Sleep Quality Index, a value of 4.75 ± 2.29 on a scale of 0-21 was observed, with no significant differences between the clubs evaluated (p > 0.05). Based on the results obtained, Chilean male professional soccer players present good sleep quality. However, the high values of "sleep latency" and "sleep disturbances" are indicators that should be worked on by the multidisciplinary team of each professional club. They should develop strategies to improve sleep hygiene, encourage good sleep, and fall asleep efficiently.

Breakfast: A Crucial Meal for Adolescents' Cognitive Performance According to Their Nutritional Status. The Cogni-Action Project.

This study aimed to determine whether pupils who have breakfast just before a cognitive demand, do not regularly skip breakfast, and consume a high-quality breakfast present higher cognitive performance than those who do not; furthermore, to establish differences according to their nutritional status. In this study, 1181 Chilean adolescents aged 10-14 years participated. A global cognitive score was computed through eight tasks, and the body mass index z-score (BMIz) was calculated using a growth reference for school-aged adolescents. The characteristics of breakfast were self-reported. Analyses of covariance were performed to determine differences in cognitive performance according to BMIz groups adjusted to sex, peak height velocity, physical fitness global score, and their schools. A positive association was found in adolescents' cognitive performance when they had breakfast just before cognitive tasks, did not regularly skip breakfast, presented at least two breakfast quality components, and included dairy products. No significant differences were found between breakfast components, including cereal/bread and fruits/fruit juice. Finally, pupils who were overweight/obese who declared that they skipped breakfast regularly presented a lower cognitive performance than their normal-BMIz peers. These findings suggest that adolescents who have breakfast just prior to a cognitive demand and regularly have a high quality breakfast have better cognitive performance than those who do not. Educative nutritional strategies should be prioritized, especially in "breakfast skippers" adolescents living with overweight/obesity.

Composición corporal y proporcionalidad en futbolistas chilenos: diferencias entre categorías juveniles y campeones profesionales / Body composition and proportionality in Chilean soccer players: sifferences between young and champion elite players

RESUMEN: El fútbol es el deporte más popular del mundo, por lo que las variables que benefician el rendimiento y el éxito deportivo generan un gran interés y ocupan un rol esencial en la preparación de futbolistas. Por lo tanto, el objetivo del presente estudio fue analizar la composición corporal y la proporcionalidad según la categoría y posición de juego. Se evaluaron a través de antropometría a 111 futbolistas de la selección chilena de fútbol en las categorías sub-15 (14,6±0,3 años), sub-17 (16,3±0,5 años), sub-20 (19,0±0,7 años) y elite (24,3±4,7 años); la significación se estableció en p<.05. En cuanto al peso, los porteros tuvieron el valor más alto para su posición; la categoría sub-20 obtuvo el valor más alto (83,7±3,8 kg). En cuanto a la estatura, los defensas centrales elite y la categoría sub-17 tuvieron los valores más altos (187,0±4,2 cm y 179,9±3,5 cm, respectivamente). Los porteros de todas las categorías tienen los mayores valores de IMC, siendo la categoría elite el más alto (25,1±1,3 kg/m2). Los delanteros/extremos sub-17 años tienen los valores más altos de masa muscular (60,5±8,0 %), mientras que los laterales sub-15 tienen los valores más bajos de masa grasa (9,6±0,7 %). Los jugadores de la selección chilena de fútbol tienen valores similares a los de otras investigaciones con jugadores de la misma edad y categoría; sin embargo, las categorías más jóvenes presentan diferencias significativas en las variables que proporcionan ventajas durante un partido con la categoría elite. Por lo tanto, se debe hacer énfasis en equiparar las condiciones físicas antes de promover a un jugador a categorías de mayor edad.

SUMMARY: Soccer is the most popular sport in the world. Thus, the variables that benefit performance and success have sparked great interest and occupy an essential role in the preparation of athletes. Therefore, the aim of the present study was to analyze the body composition and proportionality according to categories and playing position. 111 male soccer players of the Chilean national soccer team under-15 (14.6±0.3 years), under-17 (16.3±0.5 years), under-20 (19.0±0.7 years), and elite (24.3±4.7 years) categories were evaluated through anthropometry. Values of body composition and proportionality were recorded and organized by position and category; significance was established at p<.05. For weight, goalkeepers had the highest for their position; under-20 players, the highest for their category (83.7±3.8 kg). Regarding height, elite and under-17 central defenders had the highest values (187.0±4.2 cm and 179.9±3.5 cm, respectively). Goalkeepers in all categories have the highest BMI values; the highest were observed in elite (25.1±1.3 kg/m2). Under-17 forwards/extremes had the highest values in terms of muscle mass percentage (60.5±8.0 %), whereas under-15 fullbacks have the lowest values in terms of fat mass (9.6±0.7 %). The players of the Chilean national soccer team have similar values to other researches with players of the same age and category; however, the younger categories have significant differences in the variables that provide advantages during a game with the elite category. Therefore, emphasis should be placed on equating physical conditions before promoting a player to the older categories.

Effects of Beta-Alanine Supplementation on Physical Performance in Aerobic-Anaerobic Transition Zones: A Systematic Review and Meta-Analysis.

Beta-alanine supplementation (BA) has a positive impact on physical performance. However, evidence showing a benefit of this amino acid in aerobic-anaerobic transition zones is scarce and the results controversial. The aim of this systematic review and meta-analysis is to analyze the effects of BA supplementation on physical performance in aerobic-anaerobic transition zones. At the same time, the effect of different dosages and durations of BA supplementation were identified. The search was designed in accordance with the PRISMA® guidelines for systematic reviews and meta-analyses and performed in Web of Science (WOS), Scopus, SPORTDiscus, PubMed, and MEDLINE between 2010 and 2020. The methodological quality and risk of bias were evaluated with the Cochrane Collaboration tool. The main variables were the Time Trial Test (TTT) and Time to Exhaustion (TTE) tests, the latter separated into the Limited Time Test (LTT) and Limited Distance Test (LDT). The analysis was carried out with a pooled standardized mean difference (SMD) through Hedges' g test (95% CI). Nineteen studies were included in the systematic review and meta-analysis, revealing a small effect for time in the TTT (SMD, -0.36; 95% CI, -0.87-0.16; I2 = 59%; p = 0.010), a small effect for LTT (SMD, 0.25; 95% CI, -0.01-0.51; I2 = 0%; p = 0.53), and a large effect for LDT (SMD, 4.27; 95% CI, -0.25-8.79; I2 = 94%; p = 0.00001). BA supplementation showed small effects on physical performance in aerobic-anaerobic transition zones. Evidence on acute supplementation is scarce (one study); therefore, exploration of acute supplementation with different dosages and formats on physical performance in aerobic-anaerobic transition zones is needed.

Effect of a Single Nutritional Intervention Previous to a Critical Period of Fat Gain in University Students with Overweight and Obesity: A Randomized Controlled Trial.

BACKGROUND: the present study aimed to investigate the effects of a single nutritional preventive session previous to a critical period linked to fat gain in university students with overweightness and obesity, emulating a nutritional session of a public health system. METHODS: In this single-blind randomized controlled trial, 23 students met all the criteria to be included (20.91 ± 2.52-year-old; 52.2% women) who were divided into two groups: intervention group (IG) and control group (CG). Fat mass (FM) by dual-energy X-ray absorptiometry (DXA), physical activity by accelerometry, feeding evaluation through three questionnaires, and a set of healthy lifestyle recommendations were evaluated before and after the national holidays (NH). RESULTS: Our findings showed that FM increased significantly in the CG, but not in the IG (CG = 428.1 g; IG = 321.9 g; Δ = 106.2 g; p = 0.654 [95% CI = -379.57, 591.92]). However, no differences were found during the NH between them (Hedges' g effect size = 0.19; p = 0.654). In addition, no statistical differences were observed between groups in feeding evaluations, the set of recommendations performed, and physical activity. CONCLUSION: a single preventive session before a critical period, using a similar counselling approach as used in the public health system, might not be enough to promote changes in eating and physical activity patterns and preventing fat gain in overweight/obese university students. Long-term interventions are a must.

Diferencias antropométricas por posición de juego en futbolistas profesionales chilenos / Anthropometric differences per playing position in Chilean professional footballers

Introducción: dadas las características del fútbol, la tendencia en la selección de estos deportistas y su asignación en determinadas posiciones de juego se han visto condicionadas por las características morfológicas que estos presenten, por lo que el conocimiento de las particularidades antropométricas por posición de juego es un antecedente relevante para los cuerpos técnicos del fútbol de élite. El objetivo de la presente investigación es identificar y comparar las características antropométricas por posición de juego de jugadores de fútbol profesional chileno. Métodos: un total de 390 futbolistas profesionales varones, pertenecientes a 15 clubes profesionales chilenos, fueron evaluados morfológicamente mediante la medición de 25 variables antropométricas, con las que se estimaron la composición corporal, el somatótipo y los Z-score de Phantom. Para la comparación de las variables entre los grupos se utilizó una prueba Chi-cuadrado con nivel de significancia de p < 0,05, utilizando el software SPSS versión 21. Resultados: se observan diferencias entre las posiciones de juego, especialmente entre los porteros y el resto de los jugadores (p < 0,001), quienes presentan más de 2 kg de masa muscular y más de 1,8 kg de masa adiposa, frente a las otras posiciones de juego. Respecto de una muestra se sujetos activos, los futbolistas presentan una composición corporal significativamente distinta; de igual manera ocurre al comparar con Phantom, donde la estatura, el peso y la masa muscular son mayores y la masa adiposa es menor. Conclusión: los futbolistas profesionales presentan diferencias por posición de juego y en comparación a otros sujetos no deportistas y a Phantom

Introduction: given the characteristics of soccer, the tendency in the selection of these athletes and their allocation in certain game positions has been conditioned by the morphological characteristics that they present, so that the knowledge of anthropometric particularities by playing position is a relevant antecedent for the technical bodies of professional football. The objective of the present investigation is to identify and compare the anthropometric characteristics by playing position of Chilean professional soccer players. Methods: a total of 390 professional male soccer players, from 15 Chilean professional clubs, were evaluated morphologically by means of the measurement of 25 anthropometric variables, with which the body composition, the somatotype and the Z-score of Phantom were estimated. A Chi-square test with significance level of p < 0.05 was used to compare the variables between groups using SPSS software others players (greater adipose and muscular mass). As for a sample of active subjects, soccer players have a significantly different body composition, similarly occurs when compared to Phantom, where height, weight and muscle mass are greater and fat mass is lower. Conclusion: professional footballers differ by game position compared to other non-sports players and Phantom

[Anthropometric differences per playing position in Chilean professional footballers]. / Diferencias antropométricas por posición de juego en futbolistas profesionales chilenos.

INTRODUCTION: Introduction: given the characteristics of soccer, the tendency in the selection of these athletes and their allocation in certain game positions has been conditioned by the morphological characteristics that they present, so that the knowledge of anthropometric particularities by playing position is a relevant antecedent for the technical bodies of professional football. The objective of the present investigation is to identify and compare the anthropometric characteristics by playing position of Chilean professional soccer players. Methods: a total of 390 professional male soccer players, from 15 Chilean professional clubs, were evaluated morphologically by means of the measurement of 25 anthropometric variables, with which the body composition, the somatotype and the Z-score of Phantom were estimated. A Chi-square test with significance level of p < 0.05 was used to compare the variables between groups using SPSS software others players (greater adipose and muscular mass). As for a sample of active subjects, soccer players have a significantly different body composition, similarly occurs when compared to Phantom, where height, weight and muscle mass are greater and fat mass is lower. Conclusion: professional footballers differ by game position compared to other non-sports players and Phantom.

INTRODUCCIÓN: Introducción: dadas las características del fútbol, la tendencia en la selección de estos deportistas y su asignación en determinadas posiciones de juego se han visto condicionadas por las características morfológicas que estos presenten, por lo que el conocimiento de las particularidades antropométricas por posición de juego es un antecedente relevante para los cuerpos técnicos del fútbol de élite. El objetivo de la presente investigación es identificar y comparar las características antropométricas por posición de juego de jugadores de fútbol profesional chileno. Métodos: un total de 390 futbolistas profesionales varones, pertenecientes a 15 clubes profesionales chilenos, fueron evaluados morfológicamente mediante la medición de 25 variables antropométricas, con las que se estimaron la composición corporal, el somatótipo y los Z-score de Phantom. Para la comparación de las variables entre los grupos se utilizó una prueba Chi-cuadrado con nivel de significancia de p < 0,05, utilizando el software SPSS versión 21. Resultados: se observan diferencias entre las posiciones de juego, especialmente entre los porteros y el resto de los jugadores (p < 0,001), quienes presentan más de 2 kg de masa muscular y más de 1,8 kg de masa adiposa, frente a las otras posiciones de juego. Respecto de una muestra se sujetos activos, los futbolistas presentan una composición corporal significativamente distinta; de igual manera ocurre al comparar con Phantom, donde la estatura, el peso y la masa muscular son mayores y la masa adiposa es menor. Conclusión: los futbolistas profesionales presentan diferencias por posición de juego y en comparación a otros sujetos no deportistas y a Phantom.

Características antropométricas de futbolistas chilenos juveniles sub 14, sub 15 y sub 16 / Anthropometric characteristics of Chilean youth soccer player sub 14, sub 15 and sub 16

El fútbol es el deporte más practicado a nivel mundial. Esta popularidad se debe a que prácticamente cualquier persona lo puede jugar de manera amateur, pero a medida que se va profesionalizando se requiere la valoración de un perfil antropométrico que favorezca un rol determinado dentro del campo de juego. El objetivo del estudio fue comparar las características antropométricas de futbolistas chilenos juveniles sub 14, sub 15 y sub 16 de acuerdo con la posición de juego y la categoría. Se evaluaron a 180 futbolistas juveniles de sexo masculino con edades entre los 13 y 16 años, pertenecientes a las divisiones inferiores de los clubes: Audax Italiano, Cobresal y Magallanes de la Región Metropolitana de Chile. Los datos se consideraron estadísticamente significativos con p < .05. Se encontraron diferencias significativas en el peso, talla, sumatoria de 6 pliegues, kilogramos de piel, grasa, masa ósea, masa residual y en todas las longitudes corporales entre jugadores de distintas posiciones de juego. Asimismo, se encontraron diferencias estadísticas en el peso, talla, kilogramos de piel, grasa, masa ósea, músculo, masa residual y en todas las longitudes corporales menos en la radial-estiloidea entre jugadores de distintas categorías. Los resultados muestran la importancia de dividir a los futbolistas juveniles en un mayor número de roles posicionales al momento de definir las características antropométricas ideales según su ubicación en el terreno de juego. Las diferencias encontradas en la composición corporal entre categorías sugieren prestar atención al desarrollo madurativo al momento de promover a algún jugador a una división mayor.

Soccer is the most practiced sport in the world. This popularity is since practically anyone can play it amateurishly, but as it becomes professionalized it requires the valuation of ananthropometric profile that favors a certain role within the playing field. The objective of the study was to compare the anthropometric characteristics of Chilean youth soccer players sub 14, sub 15 and sub 16 according to the game position and category. The number of individuals evaluated in this study was 180 male youth players in the sub 14 categories (n = 60), sub 15 (n = 58) and sub 16 (n = 62), belonging to the lower divisions of the soccer clubs: Audax Italiano (n = 62), Cobresal (n = 57) and Magallanes (n =61) from the Metropolitan Region. The sample was chosen for convenience and consists of the total of players belonging to these three categories and these three soccer teams. These players had an average training of 4 days a week with a duration of each practice session of 120 minutes, plus a match on weekends with a duration of 90 minutes. There were significant differences in all of them between different game positions. We can emphasize that the central defenses presented the greatest statistical differences in all the lengths corresponding to the lower limbs: iliospinal height (97.6 ± 3.6), trochanteric height (92.1 ± 3.3), trochanteric-tibial lateral length (45.2 ± 1.7), lateral tibial height (46.3 ± 1.8) and medial-malleolar medial tibial length (38.7 ± 2.0), whereas the archers had them in the lengths of the train superior: acromio-radial (33.0 ± 1.6), radial-styloid (27.8 ± 1.7) and styloid-dactyly medium (20.2 ± 1.0). It was also found that there are significant differences in weight among players of different categories, with those of sub 16 having the highest weight (65.7 ± 7.4) and those of sub 14 the lowest (58.7 ± 8.1). At the same time, it is shown how there are statistical differences in the size between the sub 14 division who obtained the lowest measurement on average and the other 2 series confronted, but not so between sub 15 and sub 16, the latter being those who had the highest stature on average. It is also shown as the percentage of fat mass, ranging between 24.2 % of the sub 15 division in its lower limit, and 25.2% of the sub 14 in its upper limit being all considered as "acceptable" and without statistical significance between any categories. Statistical differences were found between the sub 14 category and the sub 16 category in all body lengths except in the radial-styloid. It is also shown that there are significant differences between the sub 14 and sub 15 in the lengths: acromio-radial and trochanteric-lateral tibial and in the heights: ilio-spinal, trochanteric and lateral tibial. This is directly related to the lower average stature they present in the sub-division 14. In turn, no statistical significance was found at any length between sub-15 and sub-16 players. Likewise, statistical differences were found in the weight, height, and weight of: skin, fat, bone mass, muscle, residual mass and in all body lengths less than radial-styloid among players of different categories. The results show the importance of dividing the young players in a greater number of positional roles when defining the ideal anthropometric characteristics according to their location in the field of play. The differences found in the body composition between categories suggest paying attention to the development of maturity when promoting a player to a larger division.

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.