Effects of LBNP + specific physical exercises on leg venous hemodynamics during a 28-days -6 degrees head-down bedrest.

The mechanisms underlying increased venous distensibility during exposure to microgravity are not well known yet. However, there seems to be evidence indicating that skeletal muscle changes resulting from exposure to microgravity play a very important role. The purpose of this experiment was to test the hypothesis that leg muscles could play an important role in the changes of leg venous distensibility observed in simulated microgravity. Twelve subjects were submitted for 28 days to a -6 degrees head-down bedrest. Changes in leg vein hemodynamics (filling and emptying) have been measured by mercury strain gauge plethysmography with venous occlusion. Six of these subjects trained their lower limbs with isometric and isokinetic exercises during bedrest (group CM), while the other 6 subjects (control group, C) had no training.