While standing on a force platform, participants were subjected to passive restraint by being strapped to a vertical surface at the head, shoulders, hips, and knees. Despite the restraint, small movements of the body were possible. During restraint, there was no imposed motion of any kind. Twenty-two percent of participants became motion sick, suggesting that passive restraint during stance may be inherently nauseogenic. Motion sickness was preceded by changes in displacements of the center of pressure. During passive restraint, the amplitude of center of pressure displacements tended to increase over time for the participants who later reported motion sickness, whereas for participants who did not report motion sickness, center of pressure displacements tended to be stable over time. The results are consistent with predictions made by the postural instability theory of motion sickness (Riccio & Stoffregen, 1991).
Bibliographical noteFunding Information:
This research was supported by the National Institute on Deafness and Other Communication Disorders (R01 DC005387-01A2) and by the National Science Foundation (BCS-0236627). Thanks to Nat Hemasilpin for motion control programming and control systems engineering.