Comparison of muscle oxygen consumption measured by near infrared continuous wave spectroscopy during supramaximal and intermittent pedalling exercise

The two purposes of the present study were 1) to determine the oxygen consumption in working skeletal muscle from the oxygenation measured by near-infrared continuous-wave spectroscopy (NIRcws) with the arterial occlusion method during the resting condition, INTVT and INTMAX and 2) to examine whether the decline rate of oxygenation is related to maximal oxygen uptake. Eight healthy males (aged 19.8 +/- 0.4 yr, height 166.9 +/- 17.4 cm, weight 62.1 +/- 2.5 kg, and maximal oxygen uptake [(V) over dot O(2)max] 55.9 +/- 1.9 ml/kg.min(-1)) took part in this study. The oxygenation was measured by NIRcws during the Wingate anaerobic test (WAnT) and two intermittent pedalling exercises of VT (INTVT) and maximal (INTMAX) work intensity. The decline rates of oxygenation obtained during the resting condition, INTVT and INT(MAX)with arterial occlusion were 0.43 +/- 0.05%/sec, 4.94 +/- 0.31%/sec, and 8.16 +/- 0.38%/sec, respectively, and that during the WAnT without arterial occlusion was 8.73 +/- 0.49%/sec. The decline rate of oxygenation during the WAnT was significantly (p < 0.0001) related to maximal oxygen uptake ((V) over dot O-2-max). These findings indicate that O-2 is utilized from the early phase, even during a supramaximal pedalling exercise, and that the oxidative metabolic capacity may be a factor contributing to supramaximal exercises. Therefore the arterial occlusion method with NIRcws is suitable for the evaluation of the muscle O-2 consumption during exercise noninvasively.