Hemostatic and Inflammatory Responses to Exercise Induced Heat Stress in Normally Trained Males
Authors:
Melanie A. Cyr, Alexandra G. Harding, Anne Ledyard, Mikayla R. Nemes
Advisor:
Dr. Denise L. Smith
Abstract:
Purpose:
The purpose of this study is to examine the hemostatic and inflammatory responses
to an acute bout of exercise in the heat as compared to in thermoneutral conditions
in normally trained males.
Methods:
Nine healthy normally trained men reported between 6:30 and 9:30am and cycled at
60%VO2max for 30 min on two occasions; one exercise bout was in a thermoneutral (TN)
condition and the other was in heat stressed (HS) condition, with the order randomly
assigned. Blood was drawn from the antecubital vein before exercise following five
minutes rest on the cycle ergometer, and also immediately post-exercise.
Results:
Fibrinogen levels increased during exercise with no difference between conditions.
Plasminogen activator inhibitor (PAI-1) increased significantly with exercise in the
heat, but did not change significantly in the TN condition. There was no significant
main effect for time or condition on platelet function, prothrombin time (PT), or
activated partial thromboplastin time (aPTT). Cell adhesion molecules did not change
significantly during exercise in either the HS or TN condition, despite a strong trend
for a significant time effect. The cytokine response showed no changes during exercise
and no significant differences between conditions for both interleukin-10 (IL-10)
and tumor necrosis factor-a (TNF-a).
Conclusions:
The activation or depression of coagulation, fibrinolysis, and inflammation varies
between a thermoneutral and heat stress exercise condition, and over time. During
exercise induced heat stress, coagulation activity increased, fibrinolysis decreased,
and there was no change in PT, aPTT, platelet function, sVCAM-1 concentration, as
well as no change in IL-10 or TNF-?. In the thermoneutral environment there was an
increase in clotting activity, no change in, and no change in sVCAM-1 concentration,
PT, aPTT, platelet function, or the inflammatory response. The reported increase in
fibrinogen concentration in both conditions, but an increase in PAI-1 only in the
heat, suggests increased clotting activity during exercise performed in the heat.
This imbalance between clotting and fibrinolysis is the pathogenesis for cardiovascular
events, and requires further investigation.