Haemostatic changes in long-distance runners and their relevance to the prevention of ischaemic heart disease.

Haemostatic changes may explain the paradoxical observations that regular exercise helps to prevent ischaemic heart disease but the risk of myocardial infarction and sudden death is actually increased during exercise. This study measured relevant haemostatic variables in 100 athletes before and after races of 10-26.2 miles duration and compared resting levels in athletes with 25 non-exercising controls. Prothrombin time, kaolin cephalin clotting time, fibrinogen, factor VII, factor VIII clotting (one and two stage), von Willebrand factor antigen, euglobulin clot lysis time, fibrin degradation products, full blood count, mean platelet volume, and platelet aggregation to collagen, adrenalin and adenosine diphosphate were measured. The immediate post-race results showed the familiar rise in platelet count and factor VIII clotting but there was no evidence of consumption or thrombin modification of factor VIII clotting. Platelet aggregation to adrenalin was reduced after the race and fibrinolysis was increased (P less than 0.05). The athletes at rest showed no significant differences from controls in their coagulation factor levels but showed increased fibrinolytic activity and reduced platelet aggregation to adrenalin (P less than 0.05). These results suggest a hypocoagulable rather than a hypercoagulable state during running and are consistent with the epidemiological evidence that such exercise is beneficial in the prevention of ischaemic heart disease.