The Effects of Beetroot Juice Supplementation on Oxygen Cost of Vigorous Intensity Aerobic Exercise in Trained Endurance Athletes

Nitric oxide (NO) regulates many physiological processes critical to exercise performance. Beetroot juice (BRJ) supplementation has been shown to increase plasma nitrate, increasing NO availability. The present study investigated the effects of BRJ supplementation during vigorous intensity aerobic exercise. Using a repeated measures crossover design with a 1-wk washout period, 11 Division III collegiate distance runners (mean ± SD: age = 20.3 ± 1.1 yr; VO2 peak = 55.5 ± 8.1 mL·kg-1 ·min-1 ) consumed 120 mL·d-1 of BRJ or placebo (PL) for 4 consecutive days. On day 5 the subjects completed 5 min of treadmill running at 65%, 85%, and 100% of volume of oxygen uptake reserve (VO2R) separated by 2 min each. There were no statistically significant interactions between treatment and exercise intensity for VO2, HR, RER, and RPE. The main effect of treatment was statistically significant for VO2, where BRJ (2.43 ± 0.18 L·min-1 ) was lower compared to PL (2.49 ± 0.17 L·min-1 ), P=0.029. The main effect of treatment was not statistically significant for HR, P = 0.490; RER, P=0.462; or RPE, P=0.471. These results suggest that a 4-day treatment of 120 mL·d-1 of BRJ reduces VO2 during vigorous intensity aerobic exercise in welltrained endurance athletes.