Nitrate-rich beetroot juice ingestion reduces skeletal muscle O 2 uptake and blood flow during exercise in sedentary men
Dietary nitrate supplementation has been shown to reduce pulmonary O uptake during submaximal exercise and enhance exercise performance. However, the effects of nitrate supplementation on local metabolic and haemodynamic regulation in contracting human skeletal muscle remain unclear. To address this...
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Published in | The Journal of physiology Vol. 599; no. 23; pp. 5203 - 5214 |
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Main Authors | , , , , , |
Format | Journal Article |
Language | English |
Published |
England
01.12.2021
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Subjects | |
Online Access | Get full text |
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Summary: | Dietary nitrate supplementation has been shown to reduce pulmonary O
uptake during submaximal exercise and enhance exercise performance. However, the effects of nitrate supplementation on local metabolic and haemodynamic regulation in contracting human skeletal muscle remain unclear. To address this, eight healthy young male sedentary subjects were assigned in a randomized, double-blind, crossover design to receive nitrate-rich beetroot juice (NO3, 9 mmol) and placebo (PLA) 2.5 h prior to the completion of a double-step knee-extensor exercise protocol that included a transition from unloaded to moderate-intensity exercise (MOD) followed immediately by a transition to intense exercise (HIGH). Compared with PLA, NO3 increased plasma levels of nitrate and nitrite. During MOD, leg
and leg blood flow (LBF) were reduced to a similar extent (∼9%-15%) in NO3. During HIGH, leg
was reduced by ∼6%-10% and LBF by ∼5%-9% (did not reach significance) in NO3. Leg
kinetics was markedly faster in the transition from passive to MOD compared with the transition from MOD to HIGH both in NO3 and PLA with no difference between PLA and NO3. In NO3, a reduction in nitrate and nitrite concentration was detected between arterial and venous samples. No difference in the time to exhaustion was observed between conditions. In conclusion, elevation of plasma nitrate and nitrate reduces leg skeletal muscle
and blood flow during exercise. However, nitrate supplementation does not enhance muscle
kinetics during exercise, nor does it improve time to exhaustion when exercising with a small muscle mass. KEY POINTS: Dietary nitrate supplementation has been shown to reduce systemic O
uptake during exercise and improve exercise performance. The effects of nitrate supplementation on local metabolism and blood flow regulation in contracting human skeletal muscle remain unclear. By using leg exercise engaging a small muscle mass, we show that O
uptake and blood flow are similarly reduced in contracting skeletal muscle of humans during exercise. Despite slower
kinetics in the transition from moderate to intense exercise, no effects of nitrate supplementation were observed for
kinetics and time to exhaustion. Nitrate and nitrite concentrations are reduced across the exercising leg, suggesting that these ions are extracted from the arterial blood by contracting skeletal muscle. |
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ISSN: | 0022-3751 1469-7793 |
DOI: | 10.1113/JP281995 |