This study evaluated the prediction that postural instability would precede the subjective symptoms of motion sickness in a fixed-base flight simulator. Eight males and 6 females aged 20-42 (mean age 28) sat in a cockpit in a video projection dome and were exposed to optical flow that oscillated in the roll axis with exposure durations typical of flight simulation. The frequencies of oscillation were those that characterize spontaneous postural sway during stance. Head motion was measured prior to and during exposure to imposed optical flow. Six participants were classified as motion sick, either during or after exposure to the optical oscillation. Prior to the onset of subjective symptoms, head motion among participants who later became sick was significantly greater than among participants who did not become motion sick. Results support the postural instability theory of motion sickness.
Abstract