Abstract

Maximal VO2 on the treadmill (VO2max) and on the bicycle ergometer (VO2peak), maximal cardiac output (Qmax), by a CO2 rebreathing method, maximal heart rate (HRmax), blood hemoglobin concentration (Hb), and hematocrit (Hct) were measured on six subjects before (B) and 3 weeks after (A) prolonged exposure to chronic hypoxia. It was observed that after high-altitude exposure VO2max, VO2peak, and Qmax were lower than before, whereas Hb and Hct were larger and HRmax was unchanged. Thus, the calculated stroke volume of the heart and the Hb flow at VO2 peak were lower in A than in B, whereas the arteriovenous O2 difference was greater in A than in B. At any given submaximal work load, VO2 and HR were the same in B and in A, whereas Q was lower in A by about 2-3/min. However, because of the increased Hb, leading to a higher arterial O2 content, at any work load the O2 flow remained unchanged. Verf.-Referat