Do the kinetics of peripheral muscle oxygenation reflect systemic oxygen intake?

To examine whether the kinetics of local muscle oxygenation reflect systemic oxygen intake, we measured the kinetics of local muscle oxygenation and systemic oxygen consumption (VO2). This study included 16 healthy males who performed an exercise tolerance test on a bicycle ergometer. During the exercise test, expiratory gas analysis was performed with an expiratory gas analyzer, and the kinetics of vastus lateralis muscle oxygenation were determined by near-infrared spectroscopy (NIRS). Oxygenated hemoglobin (OxyHb) and tissue blood oxygen saturation (StO2) gradually decreased during the exercise test, while deoxygenated hemoglobin (DeoxyHb) gradually increased. We examined correlations between the mean values of these parameters, which were calculated by time-integrating the values obtained using NIRS and dividing them by the integral time, and VO2. There was a marked positive correlation between DeoxyHb and VO2 (r = 0.893-0.986), and a marked negative correlation between StO2 and VO2 (r = 0.859-0.995). There was a negative correlation between VO2 and OxyHb (r = 0.726-0.978), and no correlation between TotalHb and VO2. These results suggest that the kinetics of peripheral muscle oxygenation reflect systemic VO2.