Effect of seating, vision and direction of horizontal oscillation on motion sickness

Background: Low frequency horizontal oscillation can cause motion sickness in some forms of transport but the influence of the characteristics of the motion and the visual and postural conditions of the body on sickness are n ot known. Hypotheses: It was hypothesised that body position, vision and di rection of motion will have an effect on motion sickness. Method: There wer e 72 seated subjects who were exposed to horizontal oscillation at 0.25 Hz, 0.7 ms(-2) r.m.s. (peak-to-peak displacement of 0.8 m) for up to 30 min wh ile in 1 of 6 conditions. Three conditions involved fore-and-afr motion and three involved lateral motion. For motion in each axis, subjects sat withi n a dosed cabin with either: a) a high backrest with their eyes open; b) a low backrest with their eyes open; or c) a low backrest with their eyes clo sed and blindfolded. Subjects provided ratings of their motion sickness sym ptoms at I-min intervals during the 30-min exposures. Results: The most nau seogenic stimulus was fore-and-aft motion with a low backrest and the eyes open. Self-ratings of motion sickness susceptibility provided by subjects b efore participating in the experiment were positively correlated with their illness ratings during the experiment. Conclusions: Restraint to the upper body during exposure to horizontal acceleration may reduce the susceptibil ity to motion sickness caused by horizontal oscillation. The relative nause ogenicity of fore-and-aft and lateral oscillation depends on the support gi ven to the upper body. In the conditions of the experiment the effects of t he postural support given to the subjects and their prior susceptibility to motion sickness were greater than any effect of the visual conditions.