Off-vertical rotation: a convenient precise means of exposing the passive human subject to a rotating linear acceleration vector.

Abstract : A rotating chair modified to permit tilting of a subject up to 20 degrees from the upright was used to expose 100 normal men to an unusual vestibular stimulus, eliciting manifestations including the clinical picture of motion sickness. Through stepwise increases in angular velocity of the chair, subjects were rotated at 10 degrees tilt until they experienced mild motion sickness (a predetermined endpoint) or until a terminal velocity of 25 rpm was reached. Eighty-eight men reached the predetermined endpoint; seven additional men reached it only when the tilt angle was increased to 20 degrees; the remaining five men were shown to be highly insusceptible. The accuracy and flexibility of the method should prove to be useful in ranking persons according to their susceptibility to motion sickness and in studying the symptomatology, including the underlying central nervous system mechanisms. (Author)