The effect of three weeks ergometer training (Tr) 5 times a week for 45 min at 70% VO2max by 6 subjects on erythrocyte turnover and haemoglobin O2 affinity has been studied. Increased reticulocytosis could be observed from the second day after beginning Tr until a few days after its end, probably caused by increased erythropoietin release by the kidney. Erythrocyte destruction was most pronounced in the first and markedly reduced in the third week of Tr. Elevated glutamate oxalacetate transaminase activity and creatine as well as lowered mean corpuscular haemoglobin indicate a younger erythrocyte population in the first week of recovery. Total blood volume increased during the course of Tr by 700 ml, mainly caused by a raised plasma volume (74%). Red cell volume increased later with maximal values one week after Tr (+280 ml). In this week the standard oxygen dissociation curve was most shifted to the right (P50 increased from 3.77 +/- 0.05 kPa to 3.99 +/- 0.07 kPa) and the Bohr coefficients had their lowest values. Both effects are completely explainable by the haemoglobin O2 binding properties of young erythrocytes. After training, all parameters of physical performance (VO2max, maximal workload, heart rate during rest and exercise) were markedly improved, indicating fast adaptation mechanisms. The increased erythrocyte turnover, including higher erythropoiesis, seems to be one important part of these effects.

Three O2 dissociation curves from venous blood [taken at rest (A), after in vitro acidification with lactic acid (B), and after exhaustive exercise (C)] were determined in eight athletes twice in a year in detrained and fully trained state. The steepness of the standard O2 dissociation curve becomes greater during the training period (increase in Hill's n from 2.68 +/- 0.10 to 2.96 +/- 0.15). There was a concomitant small rise in the intraerythrocytic organic phosphate concentrations. Bohr coefficients (BC) were calculated for blood O2 saturations ranging from 10 to 80% by comparing the dissociation curves A and B ("in vitro" BC) and curves A and C ("in vivo" BC). In detrained and trained state the in vivo BC show their maximal values at low saturation levels, in contrast the in vitro BC exhibit maximal values at middle saturations. During the training period there was an increase in the in vivo BC as well as in the in vitro BC at low saturations. These alterations may lead to augmented O2 extraction from a given volume of blood by up to 15% during heavy work in trained state. The reason for these observations could be an altered erythrocyte population.

Oxygen dissociation curves (ODC) in whole blood and organic phosphate concentrations in red cells were determined in 10 highly trained male athletes (TR), 6 semitrained subjects (ST) who played sports regularly at low intensities and 8 untrained people (UT). In all groups standard ODCs (37 degrees C, pH 7.40, PCO2 approximately 43 Torr) at rest and after a short exhaustive exercise were nearly identical, but PO2 values measured immediately after blood sampling and corrected to standard conditions tended to fall to the right of the in vitro ODC. Elevated P50 in the physically active [28.65 +/- 1.4 Torr (3.81 +/- 0.18 kPa) in ST, 28.0 +/- 1.1 Torr (3.73 +/- 0.15 kPa) in TR, but 26.5 +/- 1.1 Torr (3.53 +/- 0.15 kPa) in UT] were partly caused by different [DPG] (11.9 +/- 1.3 mumol/GHb in UT, 13.3 +/- 1.5 mumol/GHb in TR, 13.8 +/- 2.2 mumol/gHb in ST). There were remarkable differences in the shape of the curves between the groups. The slope "n" in the Hill plot amounted to 2.65 +/- 0.12 in UT, 2.74 +/- in ST and 2.90 +/- 0.11 in the TR (2 p against UT less than 0.001), leading to an elevated oxygen pressure of about 2 Torr (0.27 kPa) at 20% saturation and an augmented oxygen extraction of 5--7 SO2 at a PO2 of about 15 Torr (2kPa), which might be favorable at high workloads. The reason for the phenomenon could be an increased amount of young red cells in the blood of TR, caused by exercise induced hemolysis.

Influences exerted by altitude were investigated in eight male and three female physical education students (age 26 1 SE years) during and after a ski course lasting 2 weeks. Measurements of acid-base status, oxygen dissociation curve (ODC), and different constituents of blood were performed before ascent at Hannover (55 m above sea level), after 7 and 14 days in the mountains (2200 m), and after 5, 11, and 17 days back at Hannover. Physical performance was tested at Hannover only. No significant alkalosis was observed at altitude; the red cell pH decreased by 0.05 units. In vitro buffering of blood against CO2 (-[HCO3 J/pH) improved remarkably at the end of the mountain stay by 14 mmol/1; similarly, in vivo [Lac]/pH of blood was increased by 11 mmol/1 during the 1st week after return. The ODC showed an elevation of the standard half saturation pressure (P50, pH 7.4) at altitude from 335 0.08 to 3.98 0.03 kPa. The cause was a changed Donnan equilibrium of the erythrocytes resulting from increased 2,3-diphosphoglycerate and decreased potassium concentrations. After return to Hannover the slope n of the ODC rose from 2.7 0.1 to 3.1 0.1, possibly because of a greater percentage of young red cells. The changes of buffering and ODC might contribute to a slightly improved exercise performance after the altitude stay.