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

Bentley, Rachel, Gray, Stuart R., Schwarzbauer, Christian, Dawson, Dana, Frenneaux, Michael and He, Jiabao (2014) Dietary nitrate reduces skeletal muscle oxygenation response to physical exercise: A quantitative muscle functional MRI study. Physiological Reports, 2 (7). ISSN 2051-817X

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Abstract

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:	Article
Additional Information:	© 2014 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited
Uncontrolled Keywords:	sdg 7 - affordable and clean energy ,/dk/atira/pure/sustainabledevelopmentgoals/affordable_and_clean_energy
Faculty \ School:	Faculty of Medicine and Health Sciences > Norwich Medical School
UEA Research Groups:	Faculty of Medicine and Health Sciences > Research Groups > Cardiovascular and Metabolic Health
Depositing User:	Pure Connector
Date Deposited:	24 Mar 2015 16:04
Last Modified:	07 Oct 2024 15:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/52840
DOI:	10.14814/phy2.12089

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