Coagulation And Fibrinolytic Responses To Exercise In Hot And Cold Temperatures

Abstract

Most adverse cardiovascular events are the result of an occlusive blood clot. During exercise, ischemic risk transiently increases, possibly due to exertion-related changes in coagulation and fibrinolytic activity. Previous research suggests ambient temperature affects resting coagulation and fibrinolytic potential, but the effect of heat and cold on hemostasis during exercise is unknown. PURPOSE: To assess changes in coagulation and fibrinolysis during maximal exercise in hot and cold temperatures, and to compare those responses to exercise under normal, temperate conditions. METHODS: Fifteen healthy male subjects (25.3 ± 4.3 years) completed maximal cycle ergometer exercise tests in hot (30°C), temperate (20°C) and cold (5° or 8° C) temperatures. Blood samples were obtained before and immediately after exercise and analyzed by ELISA to determine plasma concentrations of thrombin-antithrombin complex (TAT), tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1). Results were analyzed with a two-factor ANOVA using temperature and time (pre-, post-exercise) as within-subjects factors. Post-hoc pairwise comparisons were made using Fisher‘s LSD method. RESULTS: VO2peak was not different among the three temperatures (temperate = 40.7±8.7, hot = 41.8±9.4, cold = 41.2±9.2 ml/kg/min, p>0.05). A main effect of time was observed for TAT (temperate = 0.45±0.26 - 1.04±0.44 ng/ml, hot = 0.64±0.55 - 1.18±0.95 ng/ml, cold = 0.88±0.57 - 1.34±0.79 ng/ml, PRE to POST, respectively, p<0.01) 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, p<0.01). A non-significant trend was observed for the PAI-1 response to exercise (temperate = 14.5±23.7 - 12.3±20.2 IU/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). Cold temperature resulted in significantly higher TAT concentrations than temperate conditions (p=0.05). No other main effects of temperature or time x temperature interactions were observed. CONCLUSIONS: The potential for clot formation is elevated during exposure to cold temperatures. These data suggest that risk of an ischemic event may be elevated in the cold.