Evidence that myoglobin PO 2 is a non-invasive measure of in vivo skeletal muscle mitochondrial PO 2 during exercise in humans

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ID: 327513
2026
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Abstract
Muscle mitochondrial partial pressure of oxygen (P mito O 2 ) is a key determinant of skeletal muscle oxygen consumption (V̇O 2 ), metabolism, gene regulation, and adaptation in health and disease. Yet P mito O 2 remains difficult to measure directly in vivo in humans during exercise. Myoglobin-associated PO 2 (P Mb O 2 ), measured non-invasively using proton magnetic resonance spectroscopy, may provide a measure of P mito O 2 during maximal exercise in humans because Mb is coupled to mitochondrial oxygen availability and P Mb O 2 falls in the low PO 2 range expected for P mito O 2 in vivo. However, it remains unknown whether P Mb O 2 during maximal exercise varies systematically with muscle V̇O 2max , as would be expected if P Mb O 2 reflects P mito O 2 in vivo. We analyzed data from five initially sedentary males before and after 8 weeks of single-leg knee-extensor exercise (KE) training. During maximal KE under 0.12, 0.21, and 1.00 fractions of inspired oxygen (F I O 2 ), we measured P Mb O 2 using myoglobin desaturation measured by proton magnetic resonance spectroscopy and muscle V̇O 2max from leg blood flow and the arterial–femoral venous O 2 content difference. Across F I O 2 conditions, muscle V̇O 2max varied systematically with P Mb O 2 both before and after training, consistent with O 2 -dependent mitochondrial respiration. When interpreted within a canonical hyperbolic framework, the V̇O 2 –P Mb O 2 relationship yielded low apparent mitochondrial P 50 values that were broadly consistent with values reported for human skeletal muscle isolated mitochondria studied in vitro. A complementary linear P 50 analysis that did not assume a hyperbolic relationship supported the same interpretation. Together, these findings provide data-supported, proof-of-concept evidence that P Mb O 2 reflects in vivo P mito O 2 during maximal exercise in humans.
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openalex_W7207808238 Use this key to autocite in the manuscript while using SciMatic Manuscript Manager or Thesis Manager
Authors Ryan M. Broxterman, Bradley A. Ruple, Peter D. Wagner, Russell S. Richardson
Journal Food & function
Year 2026
DOI
10.1152/function.022.2026
URL
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