Prolonged physical conditioning and blood platelet release markers: a longitudinal study.

To study the long-term non-acute effect of endurance physical exercise on blood platelet activation, 20 sedentary males and 14 sedentary females were trained 3 to 4 times a week for 9 months. After 24 weeks all subjects ran a 15-km race; and after 36 weeks a half-marathon (21 km) race. Blood samples were drawn before the training programme and 5 days after both races. Median (interquartile range) platelet factor 4 and beta-thromboglobulin pretraining values for the total group were 9 (5-35) and 69 (40-495) IU/ml, respectively. During the course of the training programme, plasma platelet factor 4 concentrations rose steadily and significantly in both the male and female group (p < 0.05), together with a non-significant rise in plasma beta-thromboglobulin. At the end of the training procedure, 5 days after the half-marathon run, median (interquartile range) plasma factor 4 and beta-thromboglobulin concentrations for the total group were 150 (62-198) and 156 (84-288) IU/ml, respectively. No difference existed in median platelet factor 4 and beta-thromboglobulin concentrations of the male and female population before or during the training programme. In summary, the results of this study demonstrate that prolonged physical conditioning of increasing intensity is mainly associated with an elevation of the platelet protein platelet factor 4.