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Bentley R, Gray SR, Schwarzbauer C, et al. Dietary nitrate reduces skeletal muscle oxygenation response to physical exercise: a quantitative muscle functional MRI study. Physiol Rep. 2014;2(7)doi: 10.14814/phy2.12089.
Bentley, R., Gray, S. R., Schwarzbauer, C., Dawson, D., Frenneaux, M., & He, J. (2014). Dietary nitrate reduces skeletal muscle oxygenation response to physical exercise: a quantitative muscle functional MRI study. Physiological reports, 2(7), . https://doi.org/10.14814/phy2.12089
Bentley, Rachel, et al. "Dietary nitrate reduces skeletal muscle oxygenation response to physical exercise: a quantitative muscle functional MRI study." Physiological reports vol. 2,7 (2014). doi: https://doi.org/10.14814/phy2.12089
Bentley R, Gray SR, Schwarzbauer C, Dawson D, Frenneaux M, He J. Dietary nitrate reduces skeletal muscle oxygenation response to physical exercise: a quantitative muscle functional MRI study. Physiol Rep. 2014 Jul 22;2(7). doi: 10.14814/phy2.12089. Print 2014 Jul 01. PMID: 25052493; PMCID: PMC4187572.
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Physiol Rep. 2014 Jul 22;2(7). doi: 10.14814/phy2.12089. Print 2014 Jul 01.

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

Physiological reports

Rachel Bentley, Stuart R Gray, Christian Schwarzbauer, Dana Dawson, Michael Frenneaux, Jiabao He

Affiliations

  1. Aberdeen Biomedical Imaging Centre, School of Medicine and Dentistry, University of Aberdeen, Aberdeen, U.K.
  2. Musculoskeletal Research Programme, School of Medicine and Dentistry, University of Aberdeen, Aberdeen, U.K.
  3. Cardiovascular Research Programme, School of Medicine and Dentistry, University of Aberdeen, Aberdeen, U.K.

PMID: 25052493 PMCID: PMC4187572 DOI: 10.14814/phy2.12089

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.

© 2014 The Authors. Physiological Reports published by Wiley Periodicals, Inc. on behalf of the American Physiological Society and The Physiological Society.

Keywords: Magnetic resonance imaging; mitochondria; nitrate; peripheral vascular function; skeletal muscle exercise

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