Motion sickness, body movement, and claustrophobia during passive restraint.

Standing participants were passively restrained and exposed to oscillating visual motion. Thirty-nine percent of participants reported motion sickness. Despite passive restraint, participants exhibited displacements of the center of pressure, and prior to the onset of motion sickness the evolution of these displacements differed between participants who later became sick and those who did not. Claustrophobia occurred during restraint, but only among participants who became motion sick. The results are consistent with the postural instability theory of motion sickness. We discuss the possible relation between claustrophobia symptoms, postural movements and motion sickness incidence.