Effects of Dietary Nitrate Supplementation on Physiological Responses, Cognitive Function, and Exercise Performance at Moderate and Very-High Simulated Altitude

Abstract

Purpose: Nitric oxide (NO) bioavailability is reduced during acute altitude exposure, contributing toward the decline in physiological and cognitive function in this environment. This study evaluated the effects of nitrate (NO3−) supplementation on NO bioavailability, physiological and cognitive function, and exercise performance at moderate and very-high simulated altitude.Methods:Ten males (mean (SD): trueV˙O2max: 60.9 (10.1) ml·kg−1·min−1) rested and performed exercise twice at moderate (~14.0% O2; ~3,000 m) and twice at very-high (~11.7% O2; ~4,300 m) simulated altitude. Participants ingested either 140 ml concentrated NO3−-rich (BRJ; ~12.5 mmol NO3−) or NO3−-deplete (PLA; 0.01 mmol NO3−) beetroot juice 2 h before each trial. Participants rested for 45 min in normobaric hypoxia prior to completing an exercise task. Exercise comprised a 45 min walk at 30% trueV˙O2max and a 3 km time-trial (TT), both conducted on a treadmill at a 10% gradient whilst carrying a 10 kg backpack to simulate altitude hiking. Plasma nitrite concentration ([NO2−]), peripheral oxygen saturation (SpO2), pulmonary oxygen uptake (trueV˙O2), muscle and cerebral oxygenation, and cognitive function were measured throughout.Results: Pre-exercise plasma [NO2−] was significantly elevated in BRJ compared with PLA (p = 0.001). Pulmonary trueV˙O2 was reduced (p = 0.020), and SpO2 was elevated (p = 0.005) during steady-state exercise in BRJ compared with PLA, with similar effects at both altitudes. BRJ supplementation enhanced 3 km TT performance relative to PLA by 3.8% [1,653.9 (261.3) vs. 1718.7 (213.0) s] and 4.2% [1,809.8 (262.0) vs. 1,889.1 (203.9) s] at 3,000 and 4,300 m, respectively (p = 0.019). Oxygenation of the gastrocnemius was elevated during the TT consequent to BRJ (p = 0.011). The number of false alarms during the Rapid Visual Information Processing Task tended to be lower with BRJ compared with PLA prior to altitude exposure (p = 0.056). Performance in all other cognitive tasks did not differ significantly between BRJ and PLA at any measurement point (p ≥ 0.141).Conclusion: This study suggests that BRJ improves physiological function and exercise performance, but not cognitive function, at simulated moderate and very-high altitude.

Effects of daily ingestion of sodium bicarbonate on acid-base status and anaerobic performance during an altitude sojourn at high altitude: a randomized controlled trial

“…Dietary strategies have previously been used to attenuate the impaired exercise performance under hypoxic conditions [11][12][13]. Among these, supplementation with sodium bicarbonate (NaHCO 3 ) as an alkalotic buffer is an interesting approach to alleviate the elevated acidic stress during exercise above the lactate threshold under hypoxic conditions [11].…”

Impact of Dietary Nitrate Supplementation on Executive Function During Hypoxic Exercise

“…Indeed, a previous study showed that a single dose of NO À 3 supplementation can modulate the cerebral hemodynamics assessed by near-infrared spectroscopy (NIRS), and potentially improve executive performance in normoxia (Wightman et al, 2015). However, others have not found an improvement of executive performance with a single dose of NO À 3 supplementation during exercise in normoxia (Thompson et al, 2014), and at rest and during exercise in hypoxia (Lefferts et al, 2016;Shannon et al, 2017). In addition to these previous studies that have investigated effects of a single dose of NO À 3 supplementation on executive function, only in normoxia, consecutive days of NO À 3 supplementation improved executive performance during exercise under normoxia (Thompson et al, 2015).…”

The interactive effects of acute exercise and hypoxia on cognitive performance: A narrative review

“…22 Thus, the notion that decreased arterial desaturation is responsible for cognitive impairment appears to be extended to exercising under hypoxia. Both Bouak et al 28 and Shannon et al 32 have previously indicated that cognitive performance was impaired during/after exercise under severe hypoxia, but not moderate hypoxia. 28,32 These findings suggest that the severity of hypoxia is a critical factor in determining cognitive performance when acute exercise is performed in hypoxia.…”

“…In contrast, spatial span task performance was not impaired in the present study. The results of Bouak et al 28 and Shannon et al 32 suggest that the severity of hypoxia is one of the factors that affect the combined effects of acute exercise and hypoxia on cognitive performance.…”