| It’s all known that, military flight procedures are very complicate tasks, which require much brain load, as well as physical load. After the huge load exceeding flight personnel’s compensatory capability, they would expose to fatigue state, which would have adverse effect on physiological and psychological function. This state can cause the declining of flight performance, even impairs flight safety. Though there are many methods to assess fatigue state, but many methods have its own weakness. In recent years, more attention from researchers has been paid to the upright balance function as a result of its distinctive strengthens. Moreover, upright balance function has been tested sensitive to fatigue, and correlated with scores of some subjective scales. As for fatigue due to flight tasks, upright balance function also will play a role in this kind of fatigue. So this project will be studied through the following three parts:Part one: Role of static upright balance in assessment of fatigue due to task-loadObjective: To study the effect of 4 hours task-load on static postural control under 4 different upright postures. Based on the sensitive parameters of the selected posture sensitive to task-load, static upright balance index(SUBI) would be computed. And further correlation between SUB index and level of task load would be analyzed.Methods: 30 eligible male subjects who were selected randomly from one aviation college were asked to perform simulated combined flight tasks consecutively for 4 hours. And then their static balance function of 4 different postures was tested at 0 h, 1 h, 2 h, 3 h and 4 h during the period, as well as the tasks scores. As for the analyzing strategy, tasks scores of post task-load were compared with the scores at 0h firstly, which would make us know what the level of task load is. Secondly, the different changing traits of the four postures were analyzed with task-load continuing. And then those sensitive parameters were constructed into a static upright balance index by principle component analysis. Besides, then correlation between SUB index and task load would be analyzed.Results: After tasks are finished, the mean multi-tasks score of subjects was decreased significantly(F=4.658,P=0.008),as well as the score of dual-tasks(F=18.428,P<0.001), which showed that 4h task-load made subjects be in fatigue state; There were interaction between lasting time of task-load and some time-domain parameters of four postures, including effective value area(F=3.974,P=0.005), mean displacement of COP on Y axis(F=2.761,P=0.032), and weight distribution of left heel(F=5.612,P<0.001)and toes(F=5.446,P=0.001). While the posture which interfered proprioceptive sense of lower extremity was most instable. And in this condition, the gravity center of subjects moved forward instinctively, which may caused by the proprioceptive sense sensitive to task load. Then, seven sensitive parameters which had changed statistically at 3rd hour were formulated into a static upright balance index by principle component analysis as the following: SUBI=3.065F1+5.346F3+13.161F4+21.954F6+37.446WD2+115.454 EVA +114.183SDy+23.746. Besides, the linear correlation between static balance index and task-load was tested directively. And the correlation between tasks scores and static balance function was similar as the relationship between tasks scores and task load level. Conclusions: In the one hand, the postures that proprioceptive sense of lower extremity was disturbed only was more sensitive to simulated flight tasks load than the other three in this experiment. Under this condition, subjects tended to maintain static upright balanceby leaning forward. In the other hand, static upright balance function could reflect the level of tasks load to some extend indirectly, and may have the early warning effect on task-load. These results would lay the theoretical foundation for application of static upright balance function in tasks-load assessment.Part two: Application strategy of static upright balance function in assessment of fatigue due to task-loadObjective: To explore the data distribution of sensitive parameters and static balance index which could provide the strategy for construction of reference standard. Methods: 108 eligible college students were recruited form one military university randomly, and their static balance function of sensitive postures which had been tested in Part One of this project was measured. The date distribution of sensitive parameters and computed balance index were tested by Kolmogorov – Smirnov method(significant level is 0.1). If the dates distribution of one parameter meet normal distribution, the different reference ranges including 80%, 90%, 95%, 99% would be made through normal distribution method. If its distribution is not normal, percentile method would be used to make the reference range.Results: After removing abnormal dates of seven sensitive parameters and one balance index, the distribution shape of three parameters including frequency-domain parameter F4, time-domain parameters WD2 and SUBI were normal. While the distribution of other five parameters was skew. So based on the corresponding distribution type of different dates, their different reference range would be made respectively.Conclusions: According to the strategy of reference standard of different parameters in no task-load state, we could know easily if one subject’s static upright balance function has exceeded the upper limit. And the more balance index exceeds upper bound, the higher level of task-load reflected by static balance function would be.Part three: Role of dynamic upright balance in assessment of fatigue due to task loadObjective: To study the effect of simulated flight task load on postural adjusting ability,and further those proper postural adjusting direction and parameters sensitive to task load would be selected.Methods: 42 eligible male students were selected from one college, and were divided into two groups: task load group and control group. The subjects in task group were asked to take a two-hour multi-task, while the other group will do nothing with those tasks. Before and after the task load, the subjective fatigue scores, reaction task score, static upright balance function and dynamic postural adjusting ability of different direction needed to be measured. Then, the difference between two groups in the subjective scores, reaction task scores and static upright balance function were tested to show the level of fatigue. Consequently, the dynamic postural control ability were analyzed with independent samples t test.Results: After 2 hours task load, the subjective fatigue score, and the rate of error in per second of volunteers have increased significantly, and the static upright balance index which suggested the level of task load has also increased siginificantly. These results showed that subjects in task load has becomed fatigue in some extent.Under effect of task load, degree of adjusting accuracy has declined obviously(t=2.117, P=0.040), when the center of pressure was moved to the front point. While body leaned to left upper point, the degree of accuracy(t=3.982, P=0.001)and postural stability(t=3.288, P=0.002) also get worse significantly, and its adjusting time became shorter(t=2.460, P=0.018). Compared with control group, stability of postural control in left point, right point and left back point also get worse significantly, while its degree of accuracy and adjusting time has no difference. Besides, there were no differences in the other four points.Conclusions: Postural adjusting ability in those positions belonging to left region were tested sensitive to fatigue due to task load, especially for stability ability parameters. So dynamic postural adjusting ability can be used to assess fatigue due to task load.Above all, the simulated flight task load in this program make subjects have fatigue, which affected upright balance function most in the condition of standing on the pad. Based on the sensitive parameters of sensitive posture, static upright balance functionindex could be constructed, and this index could reflect the level of task load. And according to the reference range of sensitive parameters, someone’s fatigue state could be detected easily, which could make medical servicemen take some effective methods to improve their work performance. Besides, postural stability ability parameters in those positions belonging to left region were tested sensitive to fatigue due to task load. And dynamic postural adjusting ability could be used to assess fatigue due to task load easily if reference standard of sensitive dynamic parameters could be made by the strategy of sensitive static parameters. So static and dynamic upright balance function could be used in the assessment of fatigue due to task-load. |
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