Influence of Gravitoinertial Force Level on Apparent Magnitude of Coriolis Cross-Coupled Angular Accelerations and Motion Sickness,

Abstract : The Skylab astronauts showed a great decrease in susceptibility to motion sickness during exposure to Coriolis cross-coupled angular accelerations when tested in orbital flight. In fact, none of them reached to motion sickness endpoint inflight although each of them had preflight. We have been attempting to determine whether this decreased susceptibility is related entirely to adaptation or in part to changes in vestibular and sensory-motor function that occur virtually immediately in the microgravity conditions of orbital flight. To resolve this issue we have tested subjects separately in the free fall and high force phases of parabolic flight maneuvers and measured (1) susceptibility to motion sickness during Coriolis stimulation as a function of force level and (2) the perceived intensity of Coriolis cross-coupled angular accelerations as a function of force level. The findings are clear cut: subjects exhibit fewer and less severe symptoms of motion sickness when tested in free fall than they do for the same Coriolis stimulation in 1G; they exhibit much earlier and much more severe symptoms when tested in 2G. Ratings of the apparent intensity of Coriolis stimulation show the same pattern; subjects find that executing head movements in free fall at a particular velocity of rotation is much less stressful than in 1G; in 2G, the perceived intensity and associated discomfort are greatly increased.