The effect of dietary nitrate supplementation on resistance exercise performance: A dose-response investigation

Dietary nitrate (NO3-) can enhance skeletal muscle contractile function and explosive-type exercise by modulating type II muscle fibers; however, limited attention has been directed at exploring the optimal dosing guidelines and potential performance-enhancing effects of NO3- supplementation during resistance-type exercise. The purpose of our investigation was to examine potential dose-response effects of concentrated NO3--rich beetroot juice on neuromuscular performance during resistance exercise. Eighteen resistance-trained men were assigned in a double-blind, randomized, crossover design, to four conditions to consume beetroot juice containing: negligible NO3- (PL); similar to 6 mmol NO3- (BR-LOW); similar to 12 mmol NO3- (BR-MOD); and similar to 24 mmol NO3- (BR-HIGH). Participants completed 1 set of vertical countermovement jumps (CMJ), 2 sets x 3 repetitions of barbell back squats, and 2 sets x 3 repetitions of barbell bench press 2.5 h post-supplementation. Plasma [NO3-] increased in a dose-dependent manner (P < 0.01). Plasma [nitrite] ([NO2-]) increased in all BR conditions compared to PL (P < 0.05), such that BR-MOD vs. BR-LOW (P < 0.01) and BR-LOW vs. PL (P < 0.01), but BR-HIGH was not different compared to BR-MOD (P > 0.05). Performance was not different between conditions in CMJ, 50% one-repetition maximum (1RM) and 75%1RM back squats, or 50%1RM and 75%1RM bench press (P > 0.05). The change in plasma [NO2-] was significantly correlated with peak power (r = - 0.65, P = 0.003), mean power (r = - 0.52, P = 0.03), and mean velocity (r = - 0.48, P = 0.04) during 50%1RM back squats following BR-LOW vs. PL but not in other conditions (P > 0.05). This study indicates that dietary NO3- does not impact resistance exercise performance at any of the doses assessed in the current study.