Effects of exercise and conditioning on clotting and fibrinolytic activity in men

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Abstract
Sixty healthy men in three physical fitness categories (sedentary, on no organized fitness program; joggers, running 5-15 miles/wk; and marathoners, running > 50 miles/wk) were evaluated for changes in blood clotting and fibrinolytic activity before and after maximum exercise on a treadmill according to the Bruce protocol. The rate of blood clotting, as measured by prothrombin times, partial thromboplastin times and thrombin times, was accelerated by exercise (all P < 0.005). The ability of euglobulin clots and plasma clots to lyse incorporated 125I-fibrin, termed 125I-euglobulin clot lysis (IEL) and 125I-plasma clot lysis (IPCL), were used as indexes of fibrinolytic activity. Marathoners had greater increases in fibrinolytic activity with exercise (76% compared with 63% for joggers and 55% for sendentary subjects by IEL; 427% compared with 418% for joggers and 309% for sedentary subjects by IPCL; all P < 0.05). Fibrin degradation products increased with exercise (P < 0.005 for the total group of 60 subjects). The absolute concentrations of .alpha.2-plasmin inhibitor, .alpha.2-macroglobulin, and antithrombin III increased with exercise (all P < 0.005), but when concentrations were corrected for acute shifts of plasma water during exercise, the quantity of these inhibitors actually decreased (all P < 0.005). The changes in clotting assays with exercise were not significantly correlated with changes in whole blood lactate, blood pyruvate, or rectal temperatures. Fibrinolytic assays before and after exercise correlated poorly to moderately with blood lactates (IEL:r = 0.441 and r = 0.425, respectively; IPCL: r = 0.294 and r = 0.544, respectively; all P < 0.05) but not with blood pyruvates or rectal temperatures. The increases in fibrinolytic activity with exercise were similarly moderately correlated with increases in serum lactate (IEL: r = 0.439 and IPCL: r = 0.564; both P < 0.05). These results suggest that conditioning enhances the fibrinolytic response to exercise.