ELIMINATION OR REDUCTION OF MOTION SICKNESS 



379 



flights (3| hours) and 12 percent on short 

 flights (40 minutes) (43). 



Susceptibility to Motion Sickness 



The number of persons motion sick on 

 any single cruise or flight is not necessarily- 

 equal to the number of persons who may be 

 motion sick at some time in their life. Thus, 

 the question, "Have you ever been sick?" 

 will be answered "yes" by a higher per- 

 centage of naval personnel than might ever 

 be observed to be sick on a single day aboard 

 ship. 



A group of 511 naval personnel with sea 

 experience gave questionnaire reports about 

 their frequency of seasickness (Table I) (19). 

 Only 192, or 37.6 percent, indicated they 

 were never seasick. Since the average 

 amount of sea duty was nearly two years in 

 this group, the men had had ample oppor- 

 tunity for exposure to all kinds of weather 

 at sea. The seven percent of the personnel 

 who said they were frequently or almost 

 always seasick to the point of nausea and 

 vomiting, represent the population who 

 would be most profitably screened before 

 sea duty. 



It is worth while to note that approxi- 

 mately one out of three men will never be 

 seasick. This relatively small number of 

 men who will never be seasick suggests that 

 it would be difficult to screen men to secure 

 a totally seasick-resistant group. 



A group of 1,560 male naval personnel 

 were given a questionnaire about their ex- 

 perience with various forms of motion sick- 

 ness (19) . Of all types of situations leading 

 to motion sickness, swings were most fre- 

 quently checked as producing symptoms 

 (Table II). (For any one question, the 

 number of cases is not equal to 1,560, because 

 of the lack of experience and an occasional 

 reject for an uninterpretable answer.) A 

 question about symptoms produced by ice 

 and roller skating was answered by only one 

 individual as almost always making him 

 sick; thus, the items in the questionnaire 

 were presumably answered with high dis- 



crimination. The information gathered by 

 this method approximates experimental ob- 

 servations. Of this group, 24.4 percent 

 indicated they had experienced some symp- 

 toms on a swing; whereas swing tests on 500 

 air force personnel revealed an incidence of 

 swing sickness of 28.6 percent (47). 



Elimination or Reduction of Motion 

 Sickness 



There are five general approaches to re- 

 ducing the incidence of motion sickness: (1) 

 elimination of susceptible personnel through 

 screening procedures, (2) acclimatization of 

 personnel by increasing daily exposure to 

 some form of adapting motion such as that 



TABLE I 



Susceptibility to Seasickness in 



Experienced Naval Personnel 



of a swing, (3) use of drugs, (4) design of the 

 craft or vehicle causing motion sickness, and 

 (5) control of auxiliary factors such as posi- 

 tion, posture, and vision. Each of these 

 approaches has its special advantages and 

 disadvantages. 



1. Screening procedures have the advan- 

 tage of supplying personnel who may require 

 little further attention. To the extent that 

 such procedures are effective, the use of 

 drugs, acclimatization periods, etc., is not 

 required. The disadvantages of screening 

 are that often it is not practical to eliminate 

 men who have special skills, and there may 

 not be a sufficiently large body of men to 

 draw upon to permit a necessary high rate 

 of elimination. 



2. Acclimatization to motion is a potenti- 

 ally useful technique in the treatment of 



