Investigating the Consistency of Mental Fatigue Measurements by Visual Analog Scale (VAS) and Flicker Fusion Apparatus

Mental fatigue is defined as body or soul tiredness which can be caused by stress، overwork، excessive use of drugs or physical or mental illnesses. Fatigue is one of the reasons of productivity loss as well as occurring accidents. Therefore، mental fatigue measurement is of great importance. This study was aimed to determine the consistency of mental fatigue measurement by self-reported VAS and the flicker fusion apparatus. A descriptive study was conducted on 30 students. After they had accomplished mental tasks (i. e. mathematical problem solving and responding to MMPI questionnaire)، mental fatigued was measured by self-reported VAS and flicker fusion apparatus. To analyze the results، paired sample T-test and Spearman correlation test were applied in SPSS software version 11. 5 (P<0. 05). The results of mental fatigue measurements by both methods of self-reported VAS and the flicker fusion apparatus showed significant increase in mental fatigue after finishing each of the mental tasks. But the findings revealed no consistency between the two methods. Since self-reported VAS is a subjective technique، it seems that the lack of consistency between the two methods is due to its inefficiency in the mental fatigue measurement. Therefore، further studies with more precise methods such as EEG is suggested.