Blood Fibrinolytic Activity in Man

Abstract

This investigation was undertaken in normal subjects to define the relationship between the intensity of exercise and magnitude of fibrinolytic response and to examine the effect of diurnal variations on the exercise response. Fibrinolytic activity was measured on fibrin plates and expressed as mm2. Diurnal variations occurred with lowest activity at 8:00 AM (mean, 66 mm2), and peak activity between 5:00 and 8:00 PM (mean, 266 mm2, P<0.001). Five minutes of maximal treadmill exercise caused a marked increase in mean activity from 90 to 658 mm2 (P<0.001). Five minutes of 70% maximal exercise produced no significant increase, but 30 minutes increased activity to 626 mm2 (P<0.005). In contrast, 30 minutes of 40% maximal exercise produced a small elevation from 80 to 173 mm2 (P<0.005). Maximal and 40% maximal exercise evoked greater responses at 4:00 PM than 8:00 AM. Exercise produces increases in fibrinolytic activity which are related to the relative intensity of exercise, its duration, and the time of day ...