Possibility of Monitoring Mitochondrial Activity in Isometric Exercise using NIRS

Abstract

Oxygen debt is an old but as yet unresolved issue drawing debate that mitochondrial activity can be initiated as rapidly as the initiation of work output. Recent NMR studies suggest it may take 30 second to 1 min. (1) for mitochondria to fully engage for the amount of ATP required. This is different from In Vivo studies done previously (2). In this study, we aimed to solve the problem by directly monitoring tissue oxygenation. A great advantage of using near infrared spectroscopy is that it offers oxygen information from the tissue directly rather than from blood outflow and inflow. Additionally advantageous is that the procedure is non-invasive. The NIR gives information about changes in muscle oxygenation which consist of two factors: oxygen supply or blood flow, and oxygen demand or oxygen consumption. Thus we can obtain oxygen metabolism information in the case of known blood flow by calculating the amount of deoxyhemoglobin (HB) and oxyhemoglobin (HBO₂) in an optically visible volume of the muscle (a volume not equal to anatomical volume). This sensitive hemoglobin transmits oxygenation information from smaller vessels whose diameters are less than 2 mm (3). These smaller vessels are the target of interest because this is where the oxygen is extracted to the muscle cells.