Detection of Oxygen Consumption in Different Forearm Muscles During Handgrip Exercise by Spatially Resolved Nir Spectroscopy

Muscle O2 kinetics during exercise in humans have been estimated by measuring blood flow, and arterial and venous O2 contents. To date, plethysmography and the ther-modilution method have been used for blood flow measurement. The blood flow values estimated by these methods have been considered to represent the average value for several working muscles. To estimate the venous O2 content, blood samples have been collected from the antecubital vein during handgrip exercise (Joyner et al.1992, Hartling et al. 1989) and from the femoral vein during \eg exercise (Costes et al. 1996, Richardson et al. 1995, Vollestad et al. 1990). Since these veins are relatively large, the venous O2 content estimated from the blood collected from them has also been considered to represent the average for several working muscles. Thus, in humans, O2 kinetics during exercise have been estimated as the average values for several working muscles, and differences in O2 kinetics between individual working muscles which contribute to the exercise have not been detected. The recent development of near-infrared (NIR) spectroscopy makes it possible to estimate changes in O2 levels in small blood vessels, capillaries, and intracellular O2 uptake sites (Mancini et al. 1994). The estimation of changes in O2 supply and consumption in muscle tissue has been achieved using the venous occlusion technique (Homma et al. 1996a), while tissue O2 saturation has been demonstrated using spatially resolved NIR spectroscopy (Farell et al. 1992, Tsunazawa et al. 1996). The aim of this study was to investigate differences in the O2 kinetics of two individual muscles, both working during handgrip exercise of various intensities, using spatially resolved NIR spectroscopy.