Effects of Dietary Nitrates on Time Trial Performance in Athletes with Different Training Status: Systematic Review

Abstract

Much research has been done in sports nutrition in recent years as the demand for performance-enhancing substances increases. Higher intake of nitrates from the diet can increase the bioavailability of nitric oxide (NO) via the nitrate–nitrite–NO pathway. Nevertheless, the increased availability of NO does not always lead to improved performance in some individuals. This review aims to evaluate the relationship between the athlete’s training status and the change in time trial performance after increased dietary nitrate intake. Articles indexed by Scopus and PubMed published from 2015 to 2019 were reviewed. Thirteen articles met the eligibility criteria: clinical trial studies on healthy participants with different training status (according to VO2max), conducting time trial tests after dietary nitrate supplementation. The PRISMA guidelines were followed to process the review. We found a statistically significant relationship between VO2max and ergogenicity in time trial performance using one-way ANOVA (p = 0.001) in less-trained athletes (VO2 < 55 mL/kg/min). A strong positive correlation was observed in experimental situations using a chronic supplementation protocol but not in acute protocol situations. In the context of our results and recent histological observations of muscle fibres, there might be a fibre-type specific role in nitric oxide production and, therefore, supplement of ergogenicity.

Combined Effects of Citrulline Plus Nitrate-Rich Beetroot Extract Co-Supplementation on Maximal and Endurance-Strength and Aerobic Power in Trained Male Triathletes: A Randomized Double-Blind, Placebo-Controlled Trial

“…In this regard, CIT [ 12 , 13 , 14 , 15 , 17 ] and BR (NO precursors) [ 23 , 25 , 26 , 30 , 31 , 32 ] are two nutritional supplements that could help improve performance in both exercises, involving neuromuscular strength and endurance [ 56 , 57 ]. It has been shown that NO can help athletes with functions that are closely involved in the regulation of muscle contraction, blood flow, maximal oxygen consumption during exercise, adaptations at the mitochondrial level and homeostasis of glucose and calcium [ 27 , 57 , 58 , 59 ], which in the long term can improve athletic performance [ 60 ]. These NO precursors may also improve performance in maximal and endurance strength and aerobic power tests through an increase in ATP production, improvement in contractile function and a decrease in ammonium, etc.…”

Neither Beetroot Juice Supplementation nor Increased Carbohydrate Oxidation Enhance Economy of Prolonged Exercise in Elite Race Walkers

“…Indeed, a meta-analysis of such studies conducted up until 2015 reported an overall effect size of 0.26 (0.15-0.38, p < 0.0001) for the reduction in oxygen utilisation during sub-maximal exercise, with effects being greatest during moderate and heavy intensity exercise [57]. Variability in findings around effects of nitrate supplementation on both economy and performance can be explained, in theory [19,56] and by meta-analysis, by a number of factors including the supplementation protocol (amount, type and timing) [58], the type of exercise [57] and the training status and aerobic fitness of the subject group [59,60]. The apparent lack of effect in elite endurance athletes may be a function of their athletic status (e.g., due to a superior background NO production or reduced number of Type II muscle fibres in which nitrate supplementation might be most suited to targeting conditions of hypoxia or acidosis [19,56,61,62]) as well as an interaction with the conditions of use.…”

Suplementos ergogénicos: la evidencia más allá de una moda

“…El NO es conocido como un potente vasodilatador que favorece la irrigación sanguínea hacia los músculos, mejorando el aporte de sustratos energéticos para la respiración aeróbica como oxígeno, ácidos grasos, glucosa; así como la remoción de intermediarios y desechos metabólicos (Betteridge et al, 2016). Además, el rol ergogénico de la producción de NO parece estar relacionado con el tipo de fibra muscular, siendo las fibras tipo II (glucolíticas de contracción rápida) las que se verían más beneficiadas (Hlinský et al, 2020 et al, 2009). La mayoría de los estudios de intervención que han evaluado el impacto del NO 3 sobre el rendimiento deportivo, se han realizado con jugo de remolacha.…”

“…El efecto ergogénico se ha reportado mayormente en hombres jóvenes, sanos y que realizan actividad física recreativa, aunque el efecto de la suplementación se considera leve (Senefeld et al, 2020). Los efectos ergogénicos del NO 3 se han reportado mayormente en protocolos de suplementación crónica y no en suplementación aguda (Hlinský et al, 2020).…”