The Effect of Oral Contraceptives and Exercise on Hemostatic and Fibrinolytic Mechanisms in Trained Women

Abstract

Exercise increases clotting and fibrinolytic activity in humans. This has also been reported for oral contraceptive agents (OCA). We studied the effects of strenuous exercise and OCA on a number of hematological variables in 20 highly trained female athletes. Ten had been using OCA for more than a year (users). The other ten served as the control group (non-users). All subjects were exercised to exhaustion by means of a graded exercise test on a bicycle ergometer. Biochemical and cellular assays for the determination of plasma volume changes and used to standardize the intensity of exercise were performed in pre- and post-exercise blood samples. Procoagulant activity of factors XII, XI and VII were determined. High molecular weight kininogen (HMWK), α₂ -macro-globulin, and C1 -esterase inhibitor were quantified by rocket Immunoelectrophoresis using monospecific antisera. Synthetic chromogenic peptide substrates were used for the determination of plasminogen, prekallikrein, α₂,-antiplasmin, and antithrombin III. The two groups examined were anthropometrically and physically very well matched. The pre-exercise results of the groups of users demonstrated a significantly higher factor XII and plasminogen level, together with a significantly lower C1-esterase inhibitor level compared to the pre-exercise data of the group of non-users. No significant differences in pre-exercise values of factor XI, factor VII, HMWK, α₂-macro-globulin, prekallikrein, α₂-antiplasmin, and antithrombin III were observed between the groups. Exercise induced a significant decrease in all clotting and fibrinolytic variables, except factor VII and α₂-antiplasmin in the group of users. In the group of non-users, significant post-exercise decreases were observed in factor XII, HMWK, prekallikrein, and α₂-macro-globulin only. Results indicate a potentiating effect of OCA on post-exercise hemostatic and fibrinolytic changes.

Key words

oral contraceptives - exercise - clotting - fibrinolysis - training