The effect of exogenous nitrate (NO3-), ingested as beetroot juice (BRJ), was examined as a potential ergogenic aid for repeated sprint tests (RSTs) in both normoxia (NORM) and hypoxia (HYPO). Low oxygen (O2) availability, whether metabolically or through the environment, may be important for the efficacy of NO3- supplementation because NO3- is reduced to Nitric Oxide (NO) under conditions independent of O2. Eleven male (age = 21 ± 2 years, VO2peak = 68.8 ± 8.2 ml·kg-1·min-1) and 4 female (age = 21 ± 2 years, VO2peak = 58.4 ± 3.5 ml·kg-1·min-1) highly endurance trained cross-country skiers performed RSTs in four conditions: NORM preceded by BRJ; NORM preceded by PLA; HYPO preceded by BRJ; and HYPO preceded by PLA. Physiological responses including changes in resting blood pressure, within session mean heart rate, O2 saturation, and pre and post RST blood parameters were compared. A significant simple main effect was observed in mean arterial pressure (MAP) at 150 minutes [p = 0.045] post supplement ingestion demonstrating reduced MAP with BRJ (93.7 ± 3.8 mmHg) compared with PLA (95.9 ± 5.0 mmHg). Despite a slight reduction in MAP, no significant interaction for FiO2 x supplement [p = 0.88] was found on power output (PO). No significant main effect for supplement [p = 0.45] was observed on PO, but a significant main effect for fraction of inspired O2 [p = 0.001] was observed on PO with improved performance in NORM (231 ± 71 W) compared with HYPO (214 ± 64 W). BRJ does not appear to be an ergogenic aid for highly endurance trained cross country skiers performing RSTs in either NORM or HYPO.
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