Physical effort-induced decrease in apparent whole blood Hb-oxygen affinity normalized for intraerythrocytic pH (pHe) at low initial values of pHe.

Effect of physical effort on haemoglobin-oxygen affinity was studied in whole blood of 28 healthy males. In persons showing decrease in pH gradient between plasma and erythrocytes after physical effort, a parallel decrease in apparent, normalized for intraerythrocytic pH (pHe), Hb-oxygen affinity was noted. An increase in pH gradient after exercise was accompanied by increase in apparent, corrected for pHe, Hb-oxygen affinity and in blood Hb content. Correlation between exercise-induced changes in Hb-oxygen affinity and in pH gradient (-0.66) was highly significant (p less than 0.001). It is suggested that both parameters may be increased by recruitment into circulation of old erythrocytes from spleen. Decrease in both parameters may be related to low values of intraerythrocytic pH before effort. Groups of persons differing in exercise-induced changes of Hb-oxygen affinity did not differ in maximal oxygen utilization.