The effect of exercise on bleeding time and local production of prostacyclin and thromboxane

Exercise at a heart rate corresponding to 30% \(\dot V_{O_{2max} } \) for 15 min was associated with an increase in the volume of bleeding time blood from a mean of 133 µl before exercise to a mean of 218 μl during and immediately after the exercise. There was similarly an increase in thromboxane B₂ production from 6.40 nmol·l⁻¹ before to 11.50 nmol·l⁻¹. Most subjects also showed an increase in the length of the bleeding time and in the production of bleeding time 6-keto-PGF_1α. The extent of increase in the bleeding time and in production of 6-keto-PGF_1α was quite variable, with subjects showing the largest increases in bleeding time also demonstrating the greatest increases in 6-keto-PGF_1α (r=0.76,P=0.004). The ingestion of aspirin before exercise markedly inhibited basal bleeding time thromboxane B₂ production and blocked the exercise-associated increments in thromboxane B₂ and 6-keto-PGF_1α production. While the aspirin itself increased the length of the bleeding time, there was not any further increase associated with exercise. In contrast to the effects of acute short-term exercise, long-distance running was associated with a significant decrease in bleeding time, but no change in bleeding time blood volume, bleeding time thromboxane B₂, or bleeding time 6-keto-PGF_1α. The results show that acute low-level exercise can be associated with significant changes in the volume of blood oozing from a bleeding time incision and in the amount of thromboxane production stimulated at the incisional site. Following exhaustive exercise of long duration, the above changes are no longer seen.