Nuancing the relationship between motion sickness and postural stability

The most cited theory on motion sickness is the conflict theory by Reason and Brand (1975) [1], stating that motion sickness occurs due to a conflict between the senses and stored patterns of motion. In addition, there seems to be evidence for another theory stating that postural instability is a necessary and sufficient condition preceding motion sickness (Riccio and Stoffregen, 1991 [2]). A number of additional observations reviewed in this paper, however, are nuancing the relationship at issue, thus devaluating the latter theory. Moreover, a central mechanism as assumed before (Bos and Bles, 2002 [20]), driving both our posture and motion sickness symptoms, may explain why and when postural instability is correlated with sickness, and when it is not.

Research highlights
► Postural instability is correlated with motion sickness severity in many studies.
► This can be explained by an observer model.
► There are, however, certain exceptions to this correlation.
► Why postural instability is not a necessary nor a sufficient condition to get sick.