| Summary: | The purpose of the current study was to assess the effects of acute and short-term nitrate (NO<sub>3</sub><sup>−</sup>)-rich beetroot juice (BR) supplementation on performance outcomes and muscle oxygenation during bench press and back squat exercise. Fourteen recreationally active males were assigned in a randomized, double-blind, crossover design to supplement for 4 days in two conditions: (1) NO<sub>3</sub><sup>−</sup>-depleted beetroot juice (PL; 0.10 mmol NO<sub>3</sub><sup>−</sup> per day) and (2) BR (11.8 mmol NO<sub>3</sub><sup>−</sup> per day). On days 1 and 4 of the supplementation periods, participants completed 2 sets of 2 × 70%1RM interspersed by 2 min of recovery, followed by one set of repetitions-to-failure (RTF) at 60%1RM for the determination of muscular power, velocity, and endurance. Quadriceps and pectoralis major tissue saturation index (TSI) were measured throughout exercise. Plasma [NO<sub>3</sub><sup>−</sup>] and nitrite ([NO<sub>2</sub><sup>−</sup>]) were higher after 1 and 4 days of supplementation with BR compared to PL (<i>p</i> < 0.05). Quadriceps and pectoralis major TSI were not different between conditions (<i>p</i> > 0.05). The number of RTF in bench press was 5% greater after acute BR ingestion compared to PL (PL: 23 ± 4 vs. BR: 24 ± 5, <i>p</i> < 0.05). There were no differences between BR and PL for RTF for back squat or power and velocity for back squat or bench press (<i>p</i> > 0.05). These data improve understanding on the ergogenic potential of BR supplementation during resistance exercise.
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