Abstract

The purpose of this study was to determine the relationship between oxygen uptake (VO2) kinetics and oxygen supply system during constant-load exercise in the supine position. The main exercises which were carried in supine position were moderate at an intensity corresponding to 80 % of ventilatory threshold (VT) and heavy at an intensity corresponding to 20 % of the difference between VT and peak VO2. Oxygenation level was obtained from inactive muscle by near-infrared spectroscopy (NIRS). This index is used to express the distribution of oxygen supply to inactive muscle during exercise. After an exponential rise in VO2 (primary component), VO2 during moderate exercise reached a steady state, while during heavy exercise it continued to increase gradually (slow component). The HR kinetics which reflected systemic O2 supply in the supine position was similar to that of VO2 in main exercise tests. However, time constants of primary and slow components in VO2 were not significantly related to those in HR in each exercise mode. Furthermore, oxygenation level decreased after about 0.5 min from the onset of exercise and showed a minimum value at about 2 min and then recovered to the initial level during moderate and heavy exercises. Since there were no significant correlation coefficients in the time constant between VO2 and HR in each component in each exercise mode and since O2 supply to active muscle is affected by systemic O2 supply and distribution of O2 supply to inactive muscle, it is unlikely that VO2 is related to O2 supply to active muscle in supine position. Verf.-Referat