The microvibrations of the body, an index for examination stress

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Abstract
Changes of whole-body microvibrations (MV) were quantitatively analyzed in 123 voluntary subjects during two examination situations and compared with the results obtained during the ensuing vacation. The force oscillations in the three space directions were measured during quiet bipedal standing and simultaneously recorded as a time function with the rectified and integrated force-time function (= rectified impulse). The rectified impulses related to body weight were used as a measure for the MV. Immediately before the examinations, all the subjects showed high values. These decreased significantly in the control measurement if the subjects passed the exams, but remained relatively high in the subjects who failed. In all three measurements, smokers and candidates who took tranquillizers before the exams show higher MV values than do the other subjects. Females are less tense than males, a difference particularly significant in the vertical (z) direction. The rectified impulse in this direction correlates positively with the estimated cardiac output. Body weight and body length show a positive correlation with the MV values in the horizontal forward-backward (x) and vertical (z) direction. The measurement of the whole-body MV enables quantitative evaluation of the complex load due to an examination situation. The hypothesis that different types of stress or personality affect given directions in space requires further investigation.