Effect of submaximal and incremental upper extremity exercise on platelet function and the role of blood shear stress

Introduction: Platelets are involved in the pathogenesis of atherosclerosis. Although physical exercise is recommended to prevent atherosclerosis, the effect of exercise on platelet function and the underlying mechanisms of these effects are not completely understood. Accordingly, we aimed to examine the effect of different intensities acute arm exercises on platelet function. In addition, we evaluated the effect of lipid peroxidation and fluid shear rate on platelet response. Materials and methods: Twenty four healthy sedentary male volunteers aged 18–24 years performed submaximal and incremental exercises by upper extremity ergometer. The shear rate in the right artery was measured by Power Doppler Ultrasound (US) at rest and immediately after exercise. Pre and postexercise maximum intensities of ADP and collagen-induced platelet aggregation were measured using the impedance technique. Bioluminescent detection of thrombin-induced platelet ATP release and measurement of thromboxane B₂ (TxB₂) levels (as a marker of thromboxane A₂ (TxA₂) formation) by enzyme-linked immunoassay were performed before and after exercise. Results and conclusion: Shear rate increased after both submaximal and incremental exercise. Collagen-induced platelet aggregation increased after submaximal exercise, while ADP-induced aggregation and thromboxane B₂ levels did not alter with this protocol. Incremental exercise caused increased collagen and ADP-induced platelet aggregation and thromboxane B₂ levels. Neither of the protocols altered platelet ATP release. It was shown that acute upper extremity exercise increased platelet aggregation, without an increase in platelet release. Collagen-induced signalling pathways were more sensitive than those induced by ADP. The increase in thromboxane B₂ after incremental exercise implied increase in thromboxane A₂ formation and lipid peroxidation. Despite a significant correlation between platelet aggregation and thromboxane B₂ levels at rest, we found no clear-cut relationship between thromboxane A₂ formation, blood shear rate and platelet response to exercise.