Motion sickness refers to a multi-system physiological syndrome caused by abnormal acceleration and motion vision scene immersion.It occurs commonly in transportation,military operations,space exploration and other fields.This article reviews recent advances in mechanism,prediction and assessment as well as control measures for motion sickness,and discusses possible research direction of motion sickness in the future.The biological basis for motion sickness sensory conflict theory has been expanded;genomic sequencing and artificial intelligence techniques have been used as novel tools for motion sickness prediction and evaluation.Acclimatization training,anti-motion sickness medication and non-drug symptom control measures used in combination is the key for motion sickness prevention and treatment.

Objective To explore the improving effects of motion sickness acclimatization training methods,namely sinusoidal vertical oscillation stimulation and sinusoidal vertical oscillation stimulation combined with visual virtual reality(VR)swell stimulation,on cognitive performance of individuals with extremely severe motion sickness.Methods A total of 90 individuals with extremely severe motion sickness screened by the Graybiel score during 6 h navigation were randomly divided into vertical group,vertical+VR group,and control group(n=30).The abilities of vigilance,memory,rapid calculation,information processing and visual manipulation were evaluated before and after the acclimatization training using a self-developed cognitive performance evaluation software.Results On the 1st day of training,the numbers of missed targets of the vertical group and vertical+VR group were increased in the vigilance test;the reaction time was prolonged in the short-term memory,rapid calculation,information processing and visual manipulation tasks;and the efficiency of rapid calculation was reduced.After acclimatization training,the numbers of missed targets were reduced to the baseline level in the vertical and vertical+VR groups,and the reaction time in the short-term memory,rapid calculation,information processing and visual manipulation tasks and the efficiency of rapid calculation were improved.Conclusion Motion sickness caused by vertical oscillation stimulation or vertical oscillation combined with visual VR swell stimulation can decrease vigilance,short-term memory,rapid calculation,information processing and visual manipulation abilities.Motion sickness acclimatization training can significantly improve the above cognitive abilities.

Objective To study the acclimatization time and effects for preventing motion sickness under sinusoidal vertical oscillation stimulation,visual virtual reality(VR)swell stimulation,and their combined stimulation.Methods Totally 120 individuals with extremely severe motion sickness during 6 h navigation were randomly divided into 4 groups(n=30):vertical group,VR group,vertical+VR group,and control group.The severity of symptoms during the training period was assessed daily by Graybiel scale,and the number of drops from flexible treadmill in the VR group was recorded.The Graybiel score of 0 for 3 d and/or the number of drops for 0 were considered as complete acclimatization.The training effect was validated by navigation under more severe sea conditions.Results The Graybiel scores of the vertical group and vertical+VR group,as well as the number of drops of the VR group were decreased with the increase of training days,and reached the acclimatization level on the 3rd,5th,and 2nd training day,respectively.The longest acclimatization time in the vertical,vertical+VR,and VR groups was 8,8,and 5 d,with an average acclimatization time of 3.6,3.9,and 2.7 d,respectively;the acclimatization rates within 5 d were 93.33％(28/30),76.67％(23/30),and 100.00％(30/30),respectively;the proportions of individuals with effective acclimatization training in the verification voyage were 86.67％(26/30),96.67％(29/30),and 66.67％(20/30),respectively;and the training efficiency was 85.19％,96.30％,and 62.97％,respectively.Conclusion Three training methods all have effects on motion sickness acclimatization,and the acclimatization period is 5-8 d.The acclimatization effects of the vertical oscillation and vertical oscillation+VR training are better than the VR training.

Objective To observe the effect of the supine-posture ripple wood training in preventing motion sickness caused by linear acceleration.Methods Totally 61 motion sickness sensitive males were screened by a vertical oscillation simulator and divided into mildly sensitive group(Graybiel score 1-15,n=28)and severely sensitive group(Graybiel score 16,n=33).The participants in the 2 groups received 5-d ripple wood training,30 min/d.The movement frequency of the ripper wood was maintained at 0.25-0.35 Hz,with an acceleration of 0.15-0.25 g.Graybiel score during the training period was recorded.The static balance function test was conducted before and after training on the 1st and 5th day.Results During the training period,the Graybiel scores and motion sickness incidence in the severely sensitive group were decreased with the increase of training days,and all participants achieved complete acclimatization on the 4th day.The Graybiel scores of the mildly sensitive group were low during the whole period,and the complete acclimatization period was 2 d.There was no significant difference in the sway area of the severely sensitive group in static balance function test before and after training(P＞0.05).The mean velocity of the severely sensitive group in static balance function test was significantly increased after training versus before training on the 1st day(P＜0.01),and there was no significant difference before and after training on the 5th day(P＞0.05).There were no significant differences in the sway area or mean velocity of the mildly sensitive group during the whole training period(all P＞0.05).The validation experiment showed that the motion sickness incidence and the symptom severity were significantly decreased in both groups;the motion sickness incidence of the mildly sensitive group decreased from 100.00％(28/28)to 35.71％(10/28);the incidence of severe symptoms in the severely sensitive group decreased from 100.00％(33/33)to 6.06％(2/33)and the vomiting incidence decreased from 96.97％(32/33)to 6.06％(2/33).Conclusion The supine-posture ripple wood training has great effect in preventing motion sickness,with widespread use and simple operation.

Objective To observe the changes of plasma gastrointestinal hormones in motion sickness sensitive and insensitive individuals before and after vertical oscillation stimulation,and to construct a susceptibility prediction model for motion sickness.Methods A total of 60 healthy male volunteers were enrolled to receive sinusoidal vertical oscillation stimulation for 45 min.The motion sickness susceptibility questionnaire(MSSQ)was filled out before the experiment.Immediately after motion,the severity of motion sickness was evaluated by Graybiel scale.The motion sickness sensitive(Graybiel score≥8 and MSSQ susceptibility index＞21,n=15)and insensitive(Graybiel score≤2 and MSSQ susceptibility index＜5,n=15)participants were screened.Plasma levels of glucagon-like peptide-1(GLP-1),cholecystokinin(CCK),leptin,ghrelin,neuropeptide Y(NPY)and orexin A(OXA)were detected by enzyme-linked immunosorbent assay before and after vertical oscillation stimulation.Logistic regression model was used to analyze the predictive effect of plasma gastrointestinal hormone levels on susceptibility to motion sickness,and a combined predictive model was established.Receiver operating characteristic(ROC)curve was used to analyze predictive value of the model.Results Ghrelin and CCK levels were significantly increased in the sensitive group after stimulation compared with those before stimulation(both P＜0.01),while NPY and leptin levels were significantly decreased(both P＜0.01).Similar results were also observed when compared with the insensitive group after stimulation.Multivariate logistic regression analysis showed that plasma ghrelin,CCK and NPY were independent predictors of susceptibility to motion sickness.The established susceptibility prediction model for motion sickness was logit(P)=-0.051 ×ghrelin+0.060× NPY-0.169 ×CCK+33.397.ROC curve analysis showed that area under curve(AUC)value of the prediction model was 0.988,the sensitivity and specificity were 100.0％and 93.3％,respectively,and the prediction effect was better than ghrelin,CCK and NPY alone(AUC=0.792,0.880,0.838).Conclusion The changes of peripheral gastrointestinal appetite regulating hormone levels may be related to the susceptibility to motion sickness.The combined use of these indicators can predict the susceptibility to motion sickness.