Noninvasive measurement of forearm oxygen consumption during exercise by near infrared spectroscopy

The evaluation of the oxygen consumption (VO2) related to muscle metabolic changes can be a very useful assessment for clinical and physiological interpretations. Local VO2 can be evaluated by measuring the VO2 changes on the whole body but this measurement is subject to a large variability and requires the assumption of a constant basal metabolism. Otherwise methods for the measurement of local VO2 are invasive and difficult to apply in dynamic conditions. A simple and non-invasive technique for the measurement of skeletal muscle VO2 could find many physiological and clinical applications in the evaluation of muscle metabolism particularly under different workload conditions. Near infrared (NIR) spectroscopy has been developed experimentally and clinically for the non-invasive monitoring of changes in brain and muscle oxygenation (Jobsis-Vander Vliet, 1977). Changes in NIR light propagation across skeletal muscle are affected by scattering and absorption effects due to haemoglobin (Hb) and myoglobin (Mb). Trends in human skeletal muscle deoxygenation have been studied previously during cuff ischaemia at rest and with extreme exercise (Hampson & Piantadosi, 1988; Chance et al., 1988; Chance et al., 1992; De Blasi et al., 1992). Although the NIR spectrum of Mb overlaps that of Hb (De Blasi et al., 1991), recently magnetic resonance spectroscopy has been employed to separate the responses of Mb and Hb to mild and severe deoxygenation (Wang et al., 1990).