Performance of near-infrared spectroscopy in measuring local O-2 consumption and blood flow in skeletal muscle

The aim of this study was to investigate local muscle O-2 consumption (musc (V) over dot o(2)) and forearm blood flow (FBF) in resting and exercising m uscle by use of near-infrared spectroscopy (NIRS) and to compare the result s with the global musc(V) over dot o(2) and FBF derived from the well-estab lished Fick method and plethysmography. musc(V) over dot o(2) was derived f rom 1) NIRS using venous occlusion, 2) NIRS using arterial occlusion, and 3 ) the Fick method [musc(V) over dot o(2(Fick))]. FBF was derived from 1) NI RS and 2) strain-gauge plethysmography. Twenty-six healthy subjects were te sted at rest and during sustained isometric handgrip exercise. Local variat ions were investigated with two independent and simultaneously operating NI RS systems at two different muscles and two measurement depths. musc(V) ove r dot o(2) increased more than fivefold in the active flexor digitorum supe rficialis muscle, and it increased 1.6 times in the brachioradialis muscle. The average increase in musc(V) over dot o(2(Fick)) was twofold. FBF incre ased 1.4 times independent of the muscle or the method. It is concluded tha t NIRS is an appropriate tool to provide information about local musc(V) ov er dot o(2) and local FBF because both place and depth of the NIRS measurem ents reveal local differences that are not detectable by the more establish ed, but also more global, Fick method.