| Abstrakt: |
The aim of this study was to evaluate the effect of incremental cycling exercise test performed before and 24 hours after blood donation (withdrawal of 450 ml of blood) on the plasma volume and concentration of morphologic elements of blood. Thirteen subjects (mean +/- SD), age 23 +/- 3 years; body mass 75 +/- 10 kg; BMI 23.4 +/- 2 kg x m(-2); VO2max 2903 +/- 334 ml x min(-1), volunteered for this study. The exercise test started at the power output of 20 W with an increase by 20 W every 3 minutes--until exhaustion. This test was performed once in the control study (7-12 days before blood donation) and repeated 24 hrs after blood donation. The blood samples were taken from the antecubital vein, in a sitting position (1) at rest, (2) at the stage of 100 W power output, (3) at the end of the test (the stage of exhaustion) and (4) at 2 hours after the end of the test. The changes in plasma volume were evaluated according to changes in hemoglobin and hematocrit concentrations. The significance of differences in the studied variables were tested using Wilcoxon test. At the end of the exercise test a significant (p<0.05) decrease in plasma volume was found in both study. It amounted to--11.1 +/- 2.9% in the control study, and to--13.0 +/- 3.9% after blood donation. Within 2 hours after the end of the exercise test plasma volume returned to the pre-exercise value in the control study and exceeded the pre-exercise value by 3.9 +/- 6.7% (p<0.05) in the study performed after blood donation. The MCV, MCH, and MCHC values were not affected by the exercise performed before and after blood donation. In the control study, at the end of the incremental exercise test a significant increase in the leukocyte, lymphocyte and thrombocyte count was found. At 2 hours after exercise thrombocytes count returned to the pre-exercise level, whereas the exercise-induced leucocytosis remained at the end-exercise level. The lymphocyte count decreased to lymphopenic level. During the incremental exercise test performed after blood donation the changes in the concentration of the studied morphologic elements of blood were similar as in the control study. The only difference was noticed in the changes of lymphocyte count which returned to the pre-exercise level within 2 hours after exhaustion. Taking into consideration the changes in plasma volume it was found that during the incremental exercise tests (both in the control study and after blood donation) there was a significant (p<0.05) extra vascular escape of erythrocytes and thrombocytes. This was accompanied by a significant accumulation of neutrophils and lymphocytes in circulating blood. At 2 hours after the end of exercise, neutrophils count increases and lymphocytes migrate into peripheral lymphoid tissues, causing lymphopenia. |
