The effects of acute exercise and increased atmospheric pressure on the hemostatic mechanism and plasma catecholamine levels.

The hemostatic response to acute exercise and increased atmospheric pressure was studied in 20 healthy male subjects (18-35 yr of age) exercised to volitional exhaustion on a cycle ergometer in a hyperbaric chamber at 3 atmospheres absolute (ATA). As a means of comparison, 6 of the 20 subjects were exercised in the same manner at 1 ATA. Similar increases in fibrinolytic activity (FA), Factor VIII activity (VIII:C), von Willebrand factor antigen (vWF:Ag) and plasma catecholamine levels were observed following acute exercise at 1 ATA and at 3 ATA. There were no changes in the levels of plasminogen, antithrombin III, Protein C or Fibrinopeptide A (FPA) with exercise either at 1 ATA or at 3 ATA. In addition, there were no changes in plasma catecholamine levels or any of the hemostatic variables measured when atmospheric pressure was increased from 1 ATA to 3ATA without exercise. These findings demonstrate that increasing atmospheric pressure from 1 ATA to 3 ATA does not alter the exercise-induced changes in hemostasis. Therefore, exercise or physical exertion at 3 ATA for a time period not to exceed 30 min does not perturb the hemostatic mechanism and increase the risk of bleeding or thrombosis.