Impact on hemostatic parameters of interrupting sitting with intermittent activity

Introduction: Excessive sitting has been associated with an elevated risk of vascular conditions, particularly venous thrombosis. Interrupting sitting time with intermittent physical activity can reduce venous stasis; however, impacts on other aspects of thrombogenesis are less understood. Purpose: To examine the effects of interrupting sitting time on blood coagulation and blood volume parameters in sedentary, middle-age, overweight/obese adults (11 men and 8 women; age = 53.8 T 4.9 yr, body mass index = 31.2 T 4.1 kgImj2; mean T SD). Methods: The randomized three-period, three-treatment acute crossover trial consisted of uninterrupted sitting and sitting interrupted by 2-min bouts of either light- or moderate-intensity treadmill walking every 20 min. In each trial condition, blood samples were collected at baseline before the consumption of a standardized meal (j2 h) and postintervention (5 h). Results: Plasma fibrinogen increased from baseline with uninterrupted sitting (0.24 gILj1, 95% confidence interval = 0.13–0.34, P G 0.001). Lightintensity but not moderate-intensity activity breaks attenuated the increase by 0.17 gILj1 (95% confidence interval = 0.01–0.32, P G 0.05). There were no between-condition differences in prothrombin time, activated partial thromboplastin time, von Willebrand
factor, D-dimer, or platelet count. Uninterrupted sitting reduced plasma volume and increased hematocrit, hemoglobin, and red blood cell count; effects attenuated by both light- and moderate-intensity breaks (P G 0.05). White blood cell count increased with uninterrupted sitting and further increased with moderate-intensity breaks. Mean platelet volume increased with moderate-intensity but not lightintensity breaks or uninterrupted sitting. Conclusion: Uninterrupted sitting increased fibrinogen and reduced plasma volume, with associated increases in hemoglobin and hematocrit. Activity breaks attenuated these responses, indicative of an ameliorating influence on the procoagulant effects of uninterrupted sitting.

Effects of long-term head-down-tilt bed rest and different training regimes on the coagulation system of healthy men

Immobility plus preexisting chronic disease or acute trauma can activate the coagulation system, thus increasing the risk for thromboembolic events. The effects of long-term bed-rest immobility and microgravity on the coagulation system of healthy persons (e.g., during crewed Mars missions) have not yet been studied. The main objective of the second Berlin BedRest Study (BBR2-2) "Coagulation Part" was to investigate adaptations of the hemostatic system during long-term bed rest (60 days) under simulated microgravity (6° head-down-tilt [6°HDT]) and after mobilization in three different volunteer groups (randomly assigned to CTR= inactive control group; RE= resistive exercise only group; and RVE= resistive exercise with whole-body vibration group). In 24 males (aged 21-45 years), before, during, and after long-term bed rest, key parameters of coagulation were measured from venous blood samples: D-dimer (DD), thrombin-antithrombin III complex (TAT), and prothrombin fragment F1 + 2 (PT-F1 + 2). Additionally, modified rotational thrombelastometry (ROTEM (®) ) analysis was performed. Times of exploratory analyses were as follows: baseline data collection 2 days before bed rest (BDC-2); eight different days of 6°HDT bed rest (HDT1-HDT60), and two different days after reambulation (R + 3 and R + 6). We found significant changes in DD, TAT, and PT-F1 + 2 over the total time course, but no consistent effect of physical interventions (RE, RVE) on these parameters. Notably, no parameter reached levels indicative of intravascular thrombin formation. All ROTEM® parameters remained within the normal range and no pathological traces were found. Sixty days of 6°HDT bed rest are not associated with pronounced activation of the coagulation system indicative of intravascular thrombus formation in healthy volunteers independent of the training type during the bed rest.