Health Adult Subjects
Conditions
Keywords
beetroot juice, exercise tolerance, muscle power, recreational athletes, acute supplementation
Brief summary
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.
Detailed description
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.
Interventions
DIETARY_SUPPLEMENTDietary Nitrate
Participants received a single acute dose of dietary nitrate before exercise. Three doses were evaluated (4.8 mmol, 8.1 mmol, and 11.3 mmol), administered approximately 2.5 hours before the treadmill running test.
OTHERPlacebo
Participants received a nitrate-depleted placebo beverage approximately 2.5 hours before the treadmill running test.
Sponsors
Universidad Autonoma de Madrid
Study design
Allocation
RANDOMIZED
Intervention model
CROSSOVER
Primary purpose
OTHER
Masking
TRIPLE (Subject, Investigator, Outcomes Assessor)
Eligibility
Sex/Gender
MALE
Age
18 Years to No maximum
Healthy volunteers
Yes
Inclusion criteria
* Male adults aged 18 to 40 years. * Recreationally trained, performing endurance or combined endurance/resistance exercise at least 3 times per week for the previous 6 months. * Maximal oxygen uptake (VO₂max) consistent with recreational training status. * Able to perform maximal treadmill running exercise. * Willing and able to comply with all study procedures. * Provided written informed consent before participation
Exclusion criteria
* Current smoking or use of nicotine products. * History of cardiovascular, pulmonary, metabolic, neurological, or musculoskeletal disorders that could affect exercise performance or participant safety. * Current use of medications or dietary supplements known to influence nitric oxide metabolism or exercise performance (e.g., nitrate supplements, phosphodiesterase-5 inhibitors, antibacterial mouthwash). * Allergy or intolerance to beetroot or any component of the study supplements. * Following a vegetarian or vegan diet, or habitually consuming a high-nitrate diet. * Consumption of alcohol, caffeine, or strenuous physical exercise within the period restricted by the study protocol before each experimental visit. * Failure to comply with pre-test dietary or behavioral instructions. Participation in another clinical trial within the previous 30 days. * Any condition that, in the opinion of the investigators, could interfere with study participation or interpretation of the results.
Design outcomes
Primary
| Measure | Time frame | Description |
|---|---|---|
| Time to Exhaustion (TTE) | Baseline (single exercise session, approximately 2.5 hours after supplementation) | Time to exhaustion during a constant-speed treadmill running test performed at the speed corresponding to the second ventilatory threshold (VT2). Time was recorded in seconds from the start of the test until volitional exhaustion. |
Secondary
| Measure | Time frame | Description |
|---|---|---|
| Countermovement Jump (CMJ) Height | Immediately before supplementation exercise and immediately after exercise | Vertical jump height assessed using a countermovement jump test before and immediately after the treadmill running test to evaluate lower-limb neuromuscular performance. |
| Drop Jump (DJ) Height | Immediately before exercise and immediately after exercise | Vertical jump height measured during a drop jump test before and immediately after the treadmill running test to assess reactive neuromuscular performance. |
| Isometric Deadlift Peak Force | Immediately before supplementation and immediately after exercise | Peak force generated during an isometric deadlift test performed before and immediately after the treadmill running test. |
| Blood Lactate Concentration | Immediately before exercise and immediately after exercise | Blood lactate concentration measured from capillary blood samples before and immediately after the treadmill running test. |
| Rating of Perceived Exertion (RPE) | Immediately after exercise | Perceived exertion assessed using the Borg Rating of Perceived Exertion Scale immediately after completion of the treadmill running test. |
Countries
Spain
Contacts
STUDY_DIRECTORHelios Pareja Galeano
Universidad Autonoma de Madrid
Outcome results
None listed