Dietary nitrate reduces skeletal muscle oxygenation response to physical exercise: a quantitative muscle functional MRI study

Bentley, R., Gray, S.R. , Schwarzbauer, C., Dawson, D., Frenneaux, M. and He, J. (2014) Dietary nitrate reduces skeletal muscle oxygenation response to physical exercise: a quantitative muscle functional MRI study. Physiological Reports, 2(7), e12089. (doi: 10.14814/phy2.12089) (PMID:25052493) (PMCID:PMC4187572)

107753.pdf - Published Version
Available under License Creative Commons Attribution.



Dietary inorganic nitrate supplementation (probably via conversion to nitrite) increases skeletal muscle metabolic efficiency. In addition, it may also cause hypoxia‐dependent vasodilation and this has the potential to augment oxygen delivery to exercising skeletal muscle. However, direct evidence for the latter with spatial localization to exercising muscle groups does not exist. We employed quantitative functional MRI (fMRI) to characterize skeletal muscle oxygen utilization and replenishment by assessment of tissue oxygenation maximal change and recovery change, respectively. Eleven healthy subjects were enrolled, of whom 9 (age 33.3 ± 4.4 years, five males) completed the study. Each subject took part in three MRI visits, with dietary nitrate (7cl concentrated beetroot juice) consumed before the third visit. During each visit fMRIs were conducted concurrently with plantar flexion exercise at workloads of 15% and 25% maximum voluntary contraction (MVC). No significant changes were found between visits 1 and 2 in the fMRI measures. A decrease in maximal change was found at 15% MVC in soleus between visits 2 and 3 (5.12 ± 2.36 to 2.55 ± 1.42, P = 0.004) and between visits 1 and 3 (4.43 ± 2.12 to 2.55 ± 1.42, P = 0.043), but not at 25% MVC or within gastrocnemius. There was no difference in recovery change between visits. We found that dietary nitrate supplementation reduces tissue oxygenation alterations during physical exercise in skeletal muscle. This effect is more prominent in muscles with predominantly type 1 fibers and at lower workloads. This indicates that in healthy subjects dietary nitrate predominantly affects skeletal muscle energy efficiency with no change in oxygen delivery.

Item Type:Articles
Glasgow Author(s) Enlighten ID:Gray, Professor Stuart
Authors: Bentley, R., Gray, S.R., Schwarzbauer, C., Dawson, D., Frenneaux, M., and He, J.
College/School:College of Medical Veterinary and Life Sciences > School of Cardiovascular & Metabolic Health
Journal Name:Physiological Reports
Publisher:Physiological Reports
ISSN (Online):2051-817X
Copyright Holders:Copyright © 2014 The Authors
First Published:First published in Physiological Reports 2(7):e12089
Publisher Policy:Reproduced under a Creative Commons License

University Staff: Request a correction | Enlighten Editors: Update this record