Near-infrared diffuse correlation spectroscopy tracks changes in oxygen delivery and utilization during exercise with and without isolated arterial compression

Near-infrared diffuse correlation spectroscopy (NW-DCS) is an emerging technology for simultaneous measurement of skeletal muscle microvascular oxygen delivery and utilization during exercise. The extent to which NIR-DCS can track acute changes in oxygen delivery and utilization has not yet been fully established. To address this knowledge gap, 14 healthy men performed rhythmic handgrip exercise at 30% maximal voluntary contraction, with and without isolated brachial artery compression, designed to acutely reduce convective oxygen delivery to the exercising muscle. Radial artery blood flow (Duplex Ultrasound) and NIR-DCS derived variables [blood flow index (BFI), tissue oxygen saturation (St(O2)), and metabolic rate of oxygen (MRO2)] were simultaneously measured. During exercise. both radial ariery blood flow (+51.6 +/- 20.3 mL/min) and DCS-derived BFI (+155.0 +/- 82.2%) increased significantly (P < 0.001), whereas St(O2) decreased -7.9 +/- 6.2% (P = 0.002) from rest. Brachial artery compression during exercise caused a significant reduction in both radial artery blood flow ( -32.0 +/- 19.5 mL/min. P = 0.001) and IX:S-derived BFI (-57.3 +/- 51.1%. P = 0.01) and a further reduction of St(O2) (-5.6 +/- 3.8%, P = 0.001) compared with exercise without compression. MRO2 was not significantly reduced during arterial compression (P = 0.83) due to compensatory reductions in S driven by increases in deoxyhemoglobin/myoglobin (+7.1 +/- 6.1 mu M, P = 0.01; an index of oxygen extraction). Together, these proof-ofconcept data help to further validate NIR-DCS as an effective tool to assess the determinants of skeletal muscle oxygen consumption at the level of the microvasculature during exercise.