Effect of temporal relationship between respiration and body motion on motion sickness.

BACKGROUND: This study investigated the effect controlling the phase of respiration on the development of nausea provoked by periodic motion at 0.2 Hz which is maximal for provocation of motion sickness. METHODS: Subjects were exposed to 60 degrees peak-peak, pitch backwards from upright motion while viewing a video of the environment with 180 degrees phase delay. Motion duration was a maximum of 30 min and frequency was set to match individuals' spontaneous respiration. Conditions were: A, spontaneous breathing; B, inspiration cued to begin when head-down; C, inspiration cued to begin when upright; D, inspiration cued with a +/-18 degrees desynchronizing phase drift with respect to the tilt cycle. Nausea was rated and ventilation was recorded. RESULTS: Magnitudes of nausea ratings were ordered D