Effects of long duration centrifugation on head movements and a psychomotor task.

Previous investigations suggest strong similarities between aftereffects of an 1.5-hour 3 gx centrifuge run (Sickness Induced by Centrifugation; SIC) and the Space Adaptation Syndrome (SAS). Head movements proved to be especially nauseogenic in both cases. Until recently, during SIC experimentation, the performance of head movements was not adequately operationalized, which hampered a statistical evaluation. For this purpose, a test was designed by which head movements in four directions (left, right, up, and down) were provoked and registered, once before and once after a 1-h 3 g centrifuge run. Subjects had to execute these head movements in order to perform well on a psychomotor task. The results indicate that the test described is sensitive in discriminating between subjects who are seriously affected after a long duration centrifugation and those who are not. Because differences in performance were found only on those parts of the task in which head movements were involved, objective evidence is obtained in favour of a vestibular cause in the etiology of SIC.