Exercise intensity: platelet function and platelet-leukocyte conjugate formation in untrained subjects

Strenuous and exhaustive exercise intensifies platelet activity as shown in the literature but effects of moderate exercise are still in discussion. The present study investigated effects of two different standardised exercise intensities controlled by individual anaerobic threshold (IAT) on platelet function and conjugate formation.

20 healthy male non-smokers underwent two exercises at 80% (moderate) of IAT which corresponded to about 57% of peak oxygen consumption (peak VO(2)) in our subjects and 100% (strenuous) of IAT, corresponding to about 69% peak VO(2). Blood samples were taken after 30 min rest and immediately after exercise. CD62P expression and differentiated platelet-leukocyte conjugates (CD45, CD14, CD41) as well as microparticles and platelet-platelet aggregates were detected flow cytometrically with and without TRAP-6-stimulation.

CD62P expression and the number of aggregates were increased (P< or =0.05) after exercise in the TRAP-stimulation experiment independent of exercise intensity. The number of platelet-granulocyte (rest 5.7+/-1.8 to post 8.1+/-1.7 (80%) vs. 6.2+/-1.9 to 10.3+/-2.0 (100%)), platelet-monocyte (5.3+/-3.6 to 8.5+/-3.7 (80%) vs. 7.4+/-3.5 to 11.7+/-4.8 (100%)), and platelet-lymphocyte conjugates (4.4+/-1.2 to 6.4+/-1.3 (80%) vs. 4.6+/-1.7 to 7.8+/-1.8% positive cells (100%)) were also higher after both exercises but increased significantly weaker (P< or =0.05) after moderate exercise. These results were confirmed by the TRAP-stimulation experiment.

Although moderate exercise led to an increase in platelet reactivity and platelet-leukocyte conjugate formation the changes in conjugate formation were significantly weaker compared to strenuous exercise. Therefore it is recommended that submaximal endurance performance should be individually developed in order for everyone to be able to carry out normal daily activities and also to exercise well below the IAT.