Effects of chronic beetroot juice supplementation on maximum oxygen uptake, velocity associated with maximum oxygen uptake, and peak velocity in recreational runners: a double-blinded, randomized and crossover study

Abstract

Purpose: This study investigated the effects of chronic 3-day beetroot juice (BRJ) supplementation on maximum oxygen uptake (VO_2max), velocity associated with VO_2max(vVO_2max), and peak velocity (V_peak) in recreational runners.

Methods: Thirteen male recreational runners (age 28.2 ± 3.0 years, height 176.8 ± 0.1 cm, body mass 74.4 ± 9.5 kg) performed four tests on a treadmill in a randomized, double-blind, crossover design: two maximum incremental tests to determine VO_2max and vVO_2max, and two tests to determine V_peak. Trials were performed following 3 days of supplementation of NO₃^--rich BRJ in natura (8.4 mmol NO₃^- day^{- 1}) or BRJ NO₃^--depleted placebo (0.01 mmol NO₃^- day^{- 1}), with the last dose being ingested 2 h before each test. During the tests, maximum heart rate (HR_max), maximal rating of perceived exertion (RPE_max), pre- and post-test glucose concentrations (Gluc_pre, Gluc_post), and peak blood lactate concentration were determined.

Results: VO_2max was higher following BRJ vs PLA (46.6 ± 6.4 vs 45.1 ± 5.8 mL kg^{- 1} min^{- 1}; P = 0.022), as well as vVO_2max (14.5 ± 0.8 vs 13.9 ± 1.0 km h^{- 1}P = 0.024) and V_peak (15.5 ± 1.1 vs 15.2 ± 1.2 km h^{- 1}P = 0.038), with no differences in the other variables.

Conclusion: Consumption of NO₃^--rich BRJ in natura (8.4 mmol NO₃^- day^{- 1}) once per day for 3 days improved VO_2max, vVO_2max and V_peak in recreational runners without changing the other analyzed variables.

Keywords: Exercise nutritional science; Nitrate supplementation; Nitric oxide; Physical endurance; Running.