Downregulation of platelet activation markers during long-term immobilization

Immobilization and sedentary lifestyle are risk factors for venous thromboembolism and cardiovascular disease, yet little is known about platelet function during long-term physical inactivity. Our aim was to investigate platelet activation markers and their coupling to standardized immobilization: platelet-derived growth factor (PDGF-BB) and P-selectin. We studied 15 healthy females participating in the Women International Space simulation for Exploration study. Following a 20-day ambulatory control period, the subjects underwent 60 days of bed rest in head-down tilt position (−6°) 24 hours a day, finalized by 20 days of recovery. The subjects were randomized into two groups during bed rest: a control group (n = 8) that remained physically inactive and an exercise group (n = 7) that participated in both supine resistance and aerobic exercise training. Blood samples for the analysis of platelet activation markers were collected at baseline (5 days before bed rest), after 44 days of bed rest and 8 days into...