The High Incidence, Heat Acclimatization And Re-adaptation After Regression Of Motion Sickness In Dampness-heat Environment

Motion sickness is considered to be a physical response to unfamiliar or incompatible motion patterns (linear motion or angular acceleration), of which main signs and symptoms include dizziness, nausea, vomiting, epigastric distress, cold sweating and pallor related to autonomic nervous system. Motion sickness is classified into car sickness, sea sickness, air sickness and etc. The mechanism of motion sickness is a quite complicated physical process, which meanwhile is influenced by various environmental factors. It shows that dampness-heat environment is not the direct cause of motion sickness but an important factor resulting in increase in incidence and aggravation of motion sickness. If the body is exposed to the dampness-heat environment, motion sickness will be easily induced under the same condition of acceleration and vestibular irritation.With continuous economic development of China, it gradually becomes more dependent on the ocean, namely more needs for the sources of the ocean. Therefore, it is urgent to protect our interests of vast ocean area. During voyage, the incidence rate of motion sickness is approximately more than 70% attributing to severe non-battle casualties. Nowadays, one of areas under threat is ocean territory (South China Sea, East China Sea and Southeast Coast of China and so on). These areas are military significance and of great importance to China's economy. In addition, these ocean territory and precious sources of China mostly locate in tropics and subtropics, in which the temperature and humidity is high. As a result, the occurrence of motion sickness is quite easy. Under this condition, it is of great importance for the Chinese military to protect our ocean territory. And motion sickness would cause non-battle casualties. Consequently, the solution to the problem of motion sickness under heat-dampness environment should be given priority. Hence, it is of far-reaching significance to establish an appropriate training method to reduce incidence of motion sickness under dampness-heat environment.The study was divided into three parts (experiments). There were 459 male cadets as subjects enrolled in the first experiment, who were given induction tests of motion sickness under room temperature (20℃, humidity 60%)and dampness-heat environment (38℃, humidity 80%). Levels of motion sickness of subjects were evaluated according to Graybiel's Score and difference between incidence under room temperature and under dampness-heat environment was discussed. In the second experiment,60 subjects suffering from motion sickness were randomly selected from 459 volunteers participating in the previous experiment. Those selected were randomized into experimental group and control experiment with 30 subjects in each group. Subjects in two groups were matched statistically. Those in experimental group were trained systematically for 10 times under dampness-heat environment (38℃, humidity 80%). Those in control group weren't trained. The induction tests were carried out after training of the experimental group and Graybiel's Score was used for evaluation. After ten times of training, incidences of two groups were observed and compared. In the last experiment, subjects in the experimental group were given induction tests ender dampness-heat environment after three months without any training. It showed that all of them didn't acclimate to dampness-heat environment and had regressed to untrained states. Then, they were re-trained to acclimate to dampness-heat environment. The time subjects spent in recovery from regression after training was observed.In the first experiment, Graybiel's Score of subjects under room temperature and dampness-heat environment were 6.53±7.36 and 7.55±6.75 (S=2756.5, P=0.0025) individually. Levels of subjects under room temperature and dampness-heat environment were defined according to Graybiel's Score, which were classified from non-symptom (N) to extreme severity (F). The number of each level in control group and experimental group were as follows: N 46,Ⅰ37,Ⅱb 47,Ⅱa 62,Ⅲ39 and F 30; N 47, I 37,Ⅱb 30,Ⅱa 32 andⅢ51 and F 64(S=2410.50, P=0.0007). In the second experiment, there were 29 subjects in each group because a subject withdrew and the one matched with it should be excluded according to the criteria. Graybiel's Score of experimental group and control group before and after training were as follows:experimental group 11.5±4.48, control group 10.5±4.67 before training (χ2=0.15, P=0.6973); experimental group 7.21±3.80, control group 10.52±4.52 after training (χ2=7.51, P=0.0082). The numbers in each level before and after training were as follows: experimental group N 2,Ⅰ0,Ⅱb 0,Ⅱa 0,Ⅲ21, F 6 (before training); N 0,Ⅰ3,Ⅱb 7, Ila 4,Ⅲ14, F 1 (after training); control group N 1, I 1,Ⅱb 0,Ⅱa 1,Ⅲ22, F 4 (before training); N 0, I 0,Ⅱb 5,Ⅱa 3, III 16, F 5 (after training). In the last experiment, subjects in the experimental group spent one month in gaining significant decrease in incidence of motion sickness in the previous experiments while they spent only 19 days in obtaining amelioration of incidence of motion sickness under the same training frequency and intensity.The following results can be obtained via the mentioned experiments:(1) The incidence rates and levels of motion sickness of heat-dampness environment group decreased significantly compared with those of control group. (2) The subjects in experimental group have acclimatized to motion sickness after training in the heat-dampness environment compared with the control group. (3) Acclimatization of the subjects in experimental group has degraded to untrained levels. Then they were trained again for only two-thirds of the time they spent in the previous training to be acclimatized to motion sickness.