Influence of Chronic Nitrate-Rich Beetroot Juice Supplementation on the Endurance Performance of Active Winter Triathletes: A Randomized Controlled Trial.

Objective: The impact of high-nitrate beetroot juice (BRJ) supplementation has seen a recent explosion of interest in sports science. This study examined the potential influence of 7-day BRJ supplementation on the endurance performance of winter triathletes.
Methods: Eighty young active winter triathletes (44 males, age = 21.50 ± 1.15 yrs; 36 females, age = 20.66 ± 1.45 yrs) participated in this study and were provided with either BRJ (6.5 mmol NO ₃ ^- /70 mL) or a placebo (PL, 0.065 mmol NO ₃ ^- /70 mL) for 7 days (a dose of ×3 per day) in a randomized, double-blind design. The athletes then completed a submaximal treadmill run, intraday cycling exhaustion testing, and a 10-km cross country (XC) skiing competition on the second day.
Results: There was a significant decrease in the oxygen uptake, respiratory exchange ratio, and blood lactic acid level ( p <  0.05) between the BRJ and PL treatment groups during V ₃ speed running (males: 13.3 km·h ^-1 , females: 11.6 km·h ^-1 ). BRJ treatment also remarkably increased the time to exhaustion (TTE) during cycling exhaustion testing (males: p  = 0.02, females: p  = 0.04). No significant differences were observed in medium- or low-speed submaximal treadmill runs and 10-km XC skiing performance.
Conclusions: One week of daily nitrate-rich BRJ supplementation improved running economy at high speed during the submaximal treadmill running test and extended the TTE of athletes during cycling exhaustion testing. However, BRJ supplementation did not improve the performance in 10-km on-snow time trials in XC skiing. Regarding nutritional strategies to improve endurance performance in exercise training and competition, these results should be carefully considered owing to the different motor skill levels and competitive abilities of participants.