Effect of roll oscillation frequency on motion sickness

BACKGROUND: In many environments associated with motion sickness there are low frequency motions in several axes, including roll. Roll motion has often been assumed to be a cause of motion sickness, either alone or in combination with motions in other axes. However, there have been no systematic studies of the effects of roll frequency on sickness. HYPOTHESIS: It was hypothesized that sickness caused by roll oscillation would depend on the frequency of roll. METHOD: There were 100 male subjects (aged 18 to 26 yr) who participated in a laboratory study. Prior to experiencing motion, all subjects completed a motion sickness history questionnaire giving information on travel and motion sickness experience. The seated subjects were exposed within a closed cabin to 30 min of sinusoidal roll motion at one of five frequencies: 0.025 Hz, 0.05 Hz, 0.10 Hz, 0.20 Hz, or 0.40 Hz. At each frequency, the cabin oscillated through +/-8 degrees about a center of rotation located on the seat surface. Ratings of motion sickness were obtained at 1-min intervals. RESULTS: Subject illness ratings were positively correlated with their previous motion sickness, although at each frequency the amount of sickness was small. Overall, there was no significant difference in the sickness ratings produced by the five motions. CONCLUSIONS: The frequency dependence of motion sickness produced by roll oscillation differs from that associated with vertical and horizontal oscillation. Motion sickness associated with pure roll oscillation of a seat will usually be less than the sickness associated with pure translational oscillation of the seat or the sickness associated with combined translation and rotation.