Purpose Physical fitness may confer protection from thrombosis; however, exercise-induced platelet activation may be involved in the triggering of acute vascular events. This study aimed to assess haemostatic responses to acute exercise in trained and sedentary middle-aged subjects. Methods 21 first class Scottish football referees and 15 sedentary controls performed a treadmill exercise test. Blood sampling was performed before, immediately after and 30 minutes post-exercise. Samples were analysed for platelet count, prothrombin time, activated partial thromboplastin time (APTT) and serum fibrinogen. Platelet activation was assessed using flow cytometry with CD62 (P-selectin) and antifibrinogen antibodies at rest and in response to ADP and epinephrine. Results Total platelet count (x 10(-9)/l) increased immediately post-exercise (228.2 (40.5), 278.6 (48.9) p = 0.001) remaining elevated at 30 minutes in both groups. APTT (s) was reduced immediately post-exercise (32.15 (3.1), 29.7 (3.94) p = 0.001) with a further reduction seen at 30 minutes (32.15 (3.1), 28.4 (3.31) p = 0.001). In the referees, percentage CD62 expression increased immediately post-exercise (0.688 (0.52), 1.42 (1.3) p = 0.008). Percentage antifibrinogen expression increased post-exercise (5.19 (4.31), 13.01 (14.24) p = 0.017), with a further increase at 30 minutes (5.19 (4.31), 20.47 (26.8) p = 0.02). Conclusion This study suggests that in an older athletic population, physical fitness does not protect against the prothrombotic effects of exercise. Our data would suggest that during a football match when referees achieve approximately 80% of peak VO2 (23) they may be at risk of significant platelet activation. Prophylactic platelet inhibition should be considered in this group after appropriate screening and risk stratification.
