Abstract

The P02 at which hemoglobin is half-saturated with 02 (P50) at 37 degrees C., PC02 = 42 Torr, measured pH and (2,3-diphosphoglycerate-to-hemoglobin concentration ratio (2,3-DPG)/(Hb)) values, Hills coefficient (n) at rest, and maximal 02 consumption (V02 max) were determined in 11 world-class professional bicycle racers off season (control, C), after 3 mo of 3 h daily training (preseason, PrS), and after additional 6 mo of competitions (competitive season, CoS). The results indicate that the P50 observed in trained athletes was the same as that of a comparable group of sendentary subjects (Sed) under the same conditions of pH, PCO2, and (2,3-DPG)/(Hb) and was similar to that obtained after normalization in respect to pH and the (2,3-DPG)/(Hb); (2,3DPG)/(Hb) increased as a function of training; the slope of the central portion of the 02 equilibrium curve (OEC) was nearly unaffected by endurance training; and V02 max increased in the course of training 7 and 9 , respectively. The V02 max predicted on the basis of a computer simulation does not increase significantly as a consequence of the measured rise in (2,3-DPG). Therefore, the observed increase of V02 max cannot be explained with adaptive changes of the OEC. The present results differ from previous findings reported in other types of athletes. Verf.-Referat