Abstract

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 Mean maximal oxygen consumption (Vo₂) (ml/kg per minute) achieved was 47.23 (5.02) in the referees and 30.1 (5.2) in sedentary controls. Total platelet count (×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). Similar trends were seen in sedentary controls.

Conclusion This study suggests that in an older athletic population, physical fitness does not protect against the prothrombotic effects of exercise. These data 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.