Am J Physiol Heart Circ Physiol. 2026 Jun 2. doi: 10.1152/ajpheart.00383.2026. Online ahead of print.
ABSTRACT
Background: Near-Infrared Spectroscopy (NIRS) is a widely used technique allowing the non-invasive measurement of skeletal muscle microvascular and mitochondrial function. However, the association between NIRS technology measurements and mitochondrial function analyzed from muscle biopsy by high-resolution respirometry is not clear. Methods: Healthy adults (n=20; 10 females; age 25.3±4.6 years) participated in the study. A NIRS device was used to measure muscle oxygenation during a 5-min brachial occlusion. Muscle oxygen consumption (mVO) and the change in tissue saturation index (TSI) from baseline to the end of occlusion (ΔTSI Base-Min) were calculated. Muscle biopsy from the vastus lateralis was collected on a separate day to assess complex I mediated mitochondrial respiration. Results: mVO (from 0.021 to 0.070 mlO/min/100g), ΔTSI Base-Min (from 25.2 to 50.2 %) and complex I mediated mitochondrial respiration (from 9.7 to 57.3 pmol·mg⁻¹·s⁻¹) showed wide interindividual variation. Complex I mediated mitochondrial respiration was correlated negatively with mVO (r=-0.64, p=0.002) and ΔTSI Base-Min (r=-0.80, p=0.0003). In multivariate linear regression analysis (Enter-method), complex I mediated respiration was the only variable significantly associated with mVO and ΔTSI Base-Min when sex, body fat percentage and peak oxygen uptake (VOpeak) during cycle ergometer test were included in the analysis as confounding factors (Standardized Coefficients ß=-0.431, p=0.017 and ß=-0.691, p=0.0006, respectively). Conclusions: Our findings suggest that during 5-min occlusion, higher mitochondrial respiratory capacity is associated with lower mVO utilization. Lower oxygen utilization during occlusion may indicate a more efficient use of oxygen by mitochondria and better preserved energy metabolism.
PMID:42227998 | DOI:10.1152/ajpheart.00383.2026