Coagulation and fibrinolytic responses to exercise and cold exposure.

This study examined the effect of acute cold exposure on coagulation (PTT) and fibrinolysis (ELT), and the effect of cooling on subsequent exercise-induced coagulation and fibrinolytic responses. Ten male volunteers were tested at 5 degrees C and 28 degrees C on alternate days. Each subject began by sitting quietly for 60 min. Each then exercised on a cycle ergometer at 50 W for 5 min followed by 150 W for 10 min. Venous blood samples were taken before rest, after rest, and after exercise for each temperature on each of the two days. PTT, ELT, and hematocrit (HCT) were determined at each interval. Rectal temperature (Tre) and mean skin temperature (Tsk) were assessed at 15-min intervals throughout. Tsk was stable under neutral conditions but declined rapidly in the cold environment. Tre response was more complex but was significantly different for one contrast only (CE less than NE). ELT was shortened to 74, 62, and 44% while HCT increased to 107, 107, and 111% of pretest values for CR, NE, and CE, respectively. No significant change was noted for PTT. It is concluded that acute cold exposure as well as exercise stress results in an increase in ELT activity of blood; simultaneous enhancement of the coagulation status of the blood in response to stress is not inextricably linked to an elevation of fibrinolytic activity, a result that questions the importance of the Hageman factor dependent pathway between coagulation and fibrinolysis.