Muscle O-2 consumption by NIRS: a theoretical model

In the past, the measurement of O-2 consumption ((O) over dot(2) ) by the m uscle could be carried out noninvasively by near-infrared spectroscopy from oxyhemoglobin and/or deoxyhemoglobin measurements only at rest or during s teady isometric contractions. In the present study, a mathematical model is developed allowing calculation,together with steady-state levels of (O) ov er dot(2), of the kinetics of (O) over dot(2) readjustment in the muscle fr om the onset of ischemic but aerobic constant-load isotonic exercises. The model, which is based on the known sequence of exoergonic metabolic pathway s involved in muscle energetics, allows simultaneous fitting of batched dat a obtained during exercises performed at different workloads. A Monte Carlo simulation has been carried out to test the quality of the model and to de fine the most appropriate experimental approach to obtain the best results. The use of a series of experimental protocols obtained at different levels of mechanical power, rather than repetitions of the same load, appears to be the most suitable procedure.