Can daily centrifugation prevent the haematocrit increase elicited by 6-degree, head-down tilt?

A measure to counteract the effects of low or zero gravity is required for long-term space flight, such as the manned Mars mission scheduled by the Na tional Aeronautics and Space administration (NASA) for 2014. We conducted a series of centrifugation experiments with humans, using a short-arm centri fuge (radius 1.8 m, made by First Medical Co., Tokyo, Japan), We employed 6 -degree, head-down tilt (HDT) for 4 days to simulate space flight. Ten heal thy male volunteers underwent 4-day HDT and a 2-G daily centrifuge load for 60 min in the +Gz direction and measurements, such as haematocrit, 24-h ur ine volume, body weight and electrocardiogram (ECG) were made. There was no significant increase in the haematocrit during the HDT period, although ou r previous studies had shown a significant increase during HDT. A 60-min da ily load of +2 Gz appears to be effective in reversing the haematocrit incr ease due to 4-day HDT.