title: Motion sickness from combined lateral and roll oscillation: effect of varying phase relationships.
abstract: BACKGROUND
  Previous studies have investigated motion sickness caused by combined lateral and roll oscillation occurring in phase with each other. In tilting trains there can be a phase difference between the two motions.
  
  
  OBJECTIVE
  It was hypothesized that sickness caused by combined lateral and roll oscillation would depend on the phase between the lateral acceleration and the roll displacement.
  
  
  METHODS
  At intervals of at least 1 wk, 20 subjects were seated in a cabin and exposed to four 30-min exposures of combined 0.2 Hz sinusoidal lateral acceleration (+/- 1.26 ms(-2)) and 0.2 Hz roll displacement (+/- 7.32 degrees). The roll oscillation had one of four phases relative to the lateral oscillation: 1) 0 degrees delay (giving 100% compensation of the lateral acceleration); 2) 14.5 degrees delay (75% compensation); 3) 29 degrees delay (50% compensation); and 4) 29 degrees advance (50% compensation). Subjects gave ratings of sickness at 1-min intervals.
  
  
  RESULTS
  Sickness was greatest with no delay (100% compensation). Increasing the delay to 14.5 degrees (75% compensation) and to 29 degrees (50% compensation) decreased sickness. Less sickness occurred when the roll displacement led the lateral acceleration by 29 degrees (phase advance) than when the roll displacement followed the lateral acceleration by 29 degrees (phase delay).
  
  
  CONCLUSIONS
  With combined lateral and roll oscillation, sickness depends on the phase between the two motions. Increasing the delay in the roll motion reduces sickness, but also reduces the compensation. There is less sickness when the roll displacement leads the lateral acceleration than when the roll displacement lags the lateral acceleration.
authors.affiliation: Human Factors Research Unit, Institute of Sound and Vibration Research, University of Southampton, Southampton SO17 1BJ, England.
authors.forename: Judith A
authors.initials: JA
authors.lastname: Joseph
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Griffin
mesh_terms: D000054:Acceleration; D000293:Adolescent; D000328:Adult; D004198:Disease Susceptibility / Q000503:physiopathology; D006801:Humans; D008297:Male; D009038:Motion; D009041:Motion Sickness / Q000503:physiopathology*; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric; D011795:Surveys and Questionnaires