Rotation at 30 RPM about the A axis after 6 hours in the 10 degree head-down position: effect on susceptibility to motion sickness.

Intraindividual differences in susceptibility to motion sickness were measured in 14 subjects for two conditions of rotation at 30 rpm in the 10 degree head-down position. In one condition, subjects were in the 10 degree head-down position for 6 h prior to the onset of rotation; in the other condition, the delay was only 15 min. In both conditions, there were changes in vital capacity, indicating a redistribution of movable body fluids. Subjects tended to be less susceptible to motion sickness when they were recumbent for 6 h prior to rotation. These results are countervidence for the hypothesis that shifts of body fluid are responsible in large part for the motion sickness elicited in orbital space flight.