Effects of Beetroot-Based Supplements on Muscular Endurance and Strength in Healthy Male Individuals: A Systematic Review and Meta-Analysis.

The aim of this study was to systematically review the current literature and analyze the effects of beetroot-based supplements (BRS) on muscular performance. Randomized controlled trials that assessed the acute or short-term effects of BRS administration on muscular endurance and/or strength in healthy male individuals were retrieved from PubMed, EMBASE, CENTRAL, and Web of Science databases from inception to February 20th, 2023. In addition, we also searched preprint papers in medRxiv.org, bibRxiv.org; thesis and dissertations included in oatd.org; and clinical trials published in ClinicalTrials.gov. Data extraction, risk of bias, and study quality were assessed by 2 authors. Meta-analyses and subgroup analyses of standardized mean differences (SMD) were performed using a random-effects model. A total of 1486 records were identified in the databases and 2 were obtained by manual search in the reference list. Of those, 27 studies attended eligibility criteria and composed this systematic review. BRS administration resulted in a positive effect on muscular endurance (SMD: 0.31; 95% confidence interval (CI): 0.10 to 0.51; p < 0.01; n = 16 studies). There was an overall significative effect for muscular strength (SMD: 0.26; 95% CI: 0.03 to 0.48; p < 0.05; n = 18 studies), but a subgroup analysis showed that significant effects were found when strength was measured in a fatigued (SMD: 0.64; 95% CI: 0.25 to 1.03; p < 0.01), but not resting state. BRS administration have a small ergogenic effect on muscular endurance and attenuate the decline in muscular strength in a fatigued state in healthy male individuals.

Beetroot-based supplements can improve muscular endurance and attenuates the decline in muscular strength. These effects are attributed to the inorganic nitrate contained in these products, which ranged from 316­985 mg/day, ingested 2­3 hours before exercise.Beetroot-based supplements administration can generate a modest increase in the number of repetitions performed to failure or in exercise time to exhaustion, which may contribute to the performance and optimization of the results of people involved in isotonic exercises (e.g., resistance training).Beetroot-based supplements ingestion can improve muscular strength, particularly it aids in the recovery of muscular strength after a fatiguing task.

Acute Effects of L-Arginine Supplementation on Oxygen Consumption Kinetics and Muscle Oxyhemoglobin and Deoxyhemoglobin during Treadmill Running in Male Adults.

L-arginine is used as a nitric oxide related supplement intended to improve sports performance, and to enhance muscular recovery during exercise. However, the literature is inconclusive. The aim of this study was to determine the effects of acute oral L-arginine supplementation on O2 consumption kinetics and local muscle blood volume and oxygenation during treadmill running at two different intensities. Using a double-blind, crossover and placebo-controlled design, 11 young healthy male adults were randomly assigned to 6 g of L-arginine (ARG) or placebo (PLA) supplementation that was ingested 60 min before the exercise test. Tests consisted of treadmill run at two different intensities (5 min each; moderate, 90% of ventilatory threshold, VT; and heavy, 50% of the difference between VT and VO2peak) interspersed by 1-min walking. Respiratory gas exchange variables were measured continuously with an automated metabolic cart. Near infrared spectroscopy (NIRS) was used to continuously monitor muscle oxyhemoglobin and deoxyhemoglobin and total hemoglobin. Blood samples were collected before supplementation and 6 min after exercise. Two-way repeated measures ANOVA did not show differences in plasma nitrite concentrations between ARG or PLA conditions during the running tests. No significant differences were observed between ARG and PLA conditions for O2 kinetics as well as for NIRS variables. ARG supplementation does not improve physiological responses associated with oxygen cost and NIRS variables during running treadmill tests. Hence, our results do not support the use of L-arginine as an ergogenic aid for running performance in young healthy males.

Combined effects of resistance training and carbohydrate-restrictive or conventional diets on weight loss, blood variables and endothelium function / Efeitos combinados do treinamento contrarresistência e dietas restritivas em carboidrato ou convencional na perda de peso, variáveis sanguíneas e função endotelial

ABSTRACT Objective: To compare the effects of either a carbohydrate-restrictive diets or a conventional hypoenergetic diet combined with resistance training. Methods: Twenty-one overweight and obese adults participated in an eight-week program consisting of progressive resistance training combined with carbohydrate-restrictive diets (initially set at <30 g carbohydrate; n=12) or conventional hypoenergetic diet (30% energetic restriction; carbohydrate/protein/lipid: 51/18/31% of total energy consumption; n=9). It was hypothesized that the carbohydrate-restrictive diets would induce greater weight loss but that both diets would elicit similar effects on selected health markers. Body mass, and body composition, blood variables and flow-mediated brachial artery dilation (flow-mediated brachial artery dilation; by ultrasound) were used to assess changes due to the interventions. Results: Significant within-group reductions in body mass (-5.4±3.5%; p=0.001 versus -3.7±3.0%; p=0.015) and body fat (body fat; -10.2±7.0%; p=0.005 versus -9.6±8.8%; p=0.017) were identified for carbohydrate-restrictive diets and conventional hypoenergetic diet, respectively, but there were no significant differences between groups as the result of the interventions. Fat free mass, blood variables and flow-mediated brachial artery dilation did not significantly change, except for the total cholesterol/high-density lipoprotein ratio, which was reduced 10.4±16.9% in carbohydrate-restrictive diets (p=0.037) and 0.5±11.3% in conventional hypoenergetic diet (p=0.398). Conclusion: Carbohydrate-restrictive diets associated with resistance training was as effective as conventional hypoenergetic diet in decreasing body mass and body fat, as well as maintaining fat free mass, blood variables and flow-mediated brachial artery dilation, however it was more effective at lowering the total cholesterol/low density lipoprotein ratio.

RESUMO Objetivo: Comparar os efeitos entre a dieta com restrição de carboidratos e a dieta hipoenergética convencional combinadas com treinamento contrarresistência. Trabalhou-se com a hipótese de que as dietas com restrição em carboidratos poderiam acarretar maior perda de peso, mas que, no entanto, ambas causariam efeitos similares nos biomarcadores de saúde. Métodos: Vinte e um adultos com sobrepeso ou obesos participaram de um programa de 8 semanas de treinamento contrarresistência progressive combinado com dieta com restrição de carboidratos (inicialmente com <30 g de carboidrato; n=12) ou com dieta hipoenergética convencional (30% de restrição energética; carboidrato/proteína/lipídeos: 51/18/31% do valor energético total; n=9). Massa e composição corporais, variáveis sanguíneas (glicose, ureia, creatinina, ácido úrico, lipemia sanguínea, proteína creativa de alta sensibilidade) e dilatação fluxo-mediada da artéria braquial (por ultrassom) foram acompanhadas para observar os efeitos das intervenções. Resultados: Foram identificadas reduções significativas na massa corporal (-5,4±3,5%; p=0,001 versus -3,7±3,0%; p=0,015) e na gordura corporal (-10,2±7,0%; p=0,005 versus -9,6±8,8%; p=0,017) de indivíduos em dieta com restrição de carboidratos e dieta hipoenergética convencional, respectivamente, sem diferenças significativas entre os grupos. Massa livre de gordura, variáveis sanguíneas e dilatação fluxo-mediada da artéria braquial não sofreram modificações significativas, exceto a razão colesterol total/lipoproteína de alta densidade, que reduziu 10,4±16,9% em dietas com restrição de carboidratos (p=0,037) e 0,5±11,3% em dieta hipoenergética convencional (p=0,398). Conclusão: A dieta com restrição de carboidratos associada ao treinamento contrarresistência foi tão efetiva quanto a dieta convencional em reduzir a massa e a gordura corporais, assim como em manter os valores da massa livre de gordura, das variáveis sanguíneas e da dilatação fluxo-mediada da artéria braquial. No entanto, foi mais efetiva na redução da razão colesterol total/lipoproteína de baixa densidade.