Dose-response Effects of Dietary Nitrate on Running Time-to-exhaustion and Neuromuscular Fatigue: a Randomized Crossover Exploratory Pilot Study

Overview

Background: Dietary nitrate is a natural compound found in vegetables such as beetroot and leafy greens. Previous research suggests that consuming nitrate before exercise may improve endurance and physical performance. However, it is still unclear whether higher doses provide greater benefits, particularly in recreationally trained individuals. Purpose: This study aimed to investigate whether different doses of dietary nitrate taken before exercise influence endurance performance and muscle fatigue during a running test in recreationally trained men. Methods: This randomized, double-blind, placebo-controlled crossover pilot study compared the effects of a placebo and three different doses of dietary nitrate consumed before exercise. On separate occasions, participants completed the same treadmill running test to exhaustion after ingesting the assigned supplement. Measures of muscle performance, blood lactate concentration, and perceived exertion were collected before and after exercise to evaluate the effects of dietary nitrate supplementation.

Dietary nitrate (NO₃-), naturally present in vegetables such as beetroot and leafy greens, can be converted into nitric oxide (NO) through the nitrate-nitrite-NO pathway. Nitric oxide plays an important role in regulating blood flow, muscle contractility, mitochondrial efficiency, and oxygen utilization during exercise. For these reasons, dietary nitrate supplementation has attracted considerable interest as a nutritional strategy to enhance exercise performance. Previous studies have reported improvements in endurance performance following acute dietary nitrate supplementation, particularly with doses between 5 and 9 mmol. However, the optimal dose for maximizing potential ergogenic effects remains uncertain, especially in recreationally trained individuals. Furthermore, limited evidence is available regarding the dose-response relationship between nitrate supplementation and exercise-induced neuromuscular fatigue. This pilot study was designed to evaluate the acute effects of three different doses of dietary nitrate compared with placebo using a randomized, double-blind, placebo-controlled crossover design. Each participant completed four experimental trials, receiving placebo or one of three nitrate doses in a randomized order before performing an identical treadmill running test to exhaustion at the speed corresponding to the second ventilatory threshold (VT2). Neuromuscular performance, blood lactate concentration, and perceived exertion were assessed before and after exercise using standardized procedures. The findings of this study are expected to contribute to a better understanding of the dose-response relationship of acute dietary nitrate supplementation and to support the design of larger clinical trials investigating its effects on endurance performance and neuromuscular function.