Background-Exercise may activate platelets and leukocytes and promote throm
bosis. The effects of aspirin treatment on the prothrombotic effects of exe
rcise have not been established.
Methods and Results-A total of 15 healthy men performed exhaustive exercise
without and with 1 week of pretreatment with aspirin (500 mg/day). Before
and immediately after exercise, platelet aggregability ex vivo was measured
by filtragometry, and venous blood samples were obtained. Whole-blood flow
cytometry was used to determine platelet and leukocyte activation and plat
elet-leukocyte aggregates. Exercise increased platelet P-selectin expressio
n, CD11b expression in neutrophils and lymphocytes, and platelet and leukoc
yte responses to thrombin. ADP. platelet activating factor, and N-formyl-me
thionyl-leucyl-phenylalanine (fMLP) in vitro. Consistent with enhanced plat
elet and leukocyte activation, more circulating platelet-platelet and plate
let-leukocyte aggregates were detected after exercise (P<0.001 for both). F
iltragometry readings were shortened, and plasma soluble P-selectin and pro
thrombin fragment 1+2 were elevated. Aspirin markedly reduced the urinary e
xcretion of 11-dehydrothromboxane B-2, decreased P-selectin expression in s
ingle platelets at rest (P<0.05), and inhibited fMLP-induced neutrophil CD1
1b expression, but it did not attenuate exercise-induced increases in plate
let aggregability, platelet P-selectin expression, leukocyte CD11b expressi
on, platelet-leukocyte aggregate formation, soluble P-selectin, or prothrom
bin fragment 1+2.
Conclusions-Exercise induced platelet and leukocyte activation and platelet
-leukocyte aggregation in vivo, and it increased platelet and leukocyte res
ponsiveness to in vitro stimulation. Aspirin treatment attenuated certain s
igns of platelet activity in vivo at rest and fMLP-induced neutrophil activ
ation in vitro, but it did not attenuate the prothrombotic effects of exerc
ise.