Motion sickness with combined fore-and-aft and pitch oscillation: effect of phase and the visual scene

Background: the view ahead influences the motion sickness of car passengers but has been found to have little influence on the sickness caused by low frequency fore-and-aft oscillation. Acceleration and deceleration of vehicles is accompanied by pitch motions that may influence sickness.Hypotheses: it was hypothesized that: 1) a visual scene would influence sickness caused by combined fore-and-aft and pitch oscillation; and 2) sickness would be dependent on the phase between the fore-and-aft oscillation and the pitch oscillation. Method: while viewing one of three visual scenes (internal view, blindfold, or external view), 6 groups of 20 subjects were exposed for 30 min to 1 of 2 motions (in-phase or out-of-phase combinations of 0.1 Hz fore-and-aft and pitch oscillation). The 0.1-Hz fore-and-aft oscillation at ± 1.26 ms-2 rms (displacement of ± 3.18 m) was combined with ± 3.69° pitch oscillation either in phase (so the pitch increased acceleration in the plane of the seat to ± 1.89 ms-2) or out of phase (to reduce acceleration to ± 0.63 ms-2). Results: with both types of motion (in-phase and out-of-phase oscillation) there was significantly less sickness with an external view than with an internal view or a blindfold. There was evidence of an interaction between the effects of viewing condition and the effect of the phase between the fore-and-aft and the pitch oscillation consistent with blindfolded subjects experiencing less sickness when they experienced greater forces. Conclusions: motion sickness caused by combined fore-and-aft and pitch oscillation depends on both the visual scene and the phase between the fore-and-aft and pitch motions. The minimization of sickness arising from such motions should involve the optimization of both the visual environment and the phase