Ambient temperature affects thrombotic potential at rest and following exercise.

INTRODUCTION: During exercise, ischemic risk increases, possibly due to changes in coagulation and fibrinolytic activity. Previous research suggests ambient temperature affects resting thrombotic potential, but the effect of heat and cold on hemostasis during exercise is unknown. The purpose of this study was to assess changes in coagulation and fibrinolysis during maximal exercise in hot and cold temperatures, and to compare those responses to exercise under temperate conditions. MATERIALS &
METHODS: Fifteen healthy men completed maximal exercise tests in hot (30°C), temperate (20°C) and cold (5° - 8°C) temperatures. Blood samples were obtained before and immediately after exercise and analyzed for concentrations of thrombin-antithrombin III (TAT), active tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1). Results were analyzed by ANOVA.
RESULTS: A main effect of time was observed for TAT (temperate=1.71 ± 0.82 - 2.61 ± 0.43 ng/ml, hot=1.81 ± 0.73 - 2.62 ± 0.67 ng/ml, cold=2.33 ± 0.65 - 2.89 ± 0.81 ng/ml, PRE to POST, respectively) and tPA activity (temperate=0.72 ± 0.44 - 2.71 ± 0.55 IU/ml, hot=0.72 ± 0.38 - 2.64 ± 0.61 IU/ml, cold=0.86 ± 0.45 - 2.65 ± 0.77 IU/ml, PRE to POST, respectively). A trend was observed for the PAI-1 response to exercise (temperate=14.5 ± 23.7 - 12.3 ± 20.2I U/ml, hot=15.1 ± 26.5 - 10.0 ± 15.1 IU/ml, cold=10.5 ± 10.4 - 7.9 ± 9.7 IU/ml, PRE to POST, respectively, p=0.08). TAT concentrations were significantly higher in cold compared to temperate and hot conditions.
CONCLUSION: Coagulation potential is elevated during exposure to cold temperatures. These data suggest that risk of an ischemic event may be elevated in the cold.