Gender difference in subjective response to whole-body vibration under standing posture

Abstract

The aim of this study was to examine whether there exist gender differences in subjective response to whole-body vibration (WBV) under standing posture. Totally twenty-four participants (twelve males and twelve females) rated the discomfort of the test stimuli. The test stimuli included fore-and-aft (x), lateral (y), and vertical (z) vibration of three intensity levels (0.2, 0.4, and 0.8 m/s(2) r.m.s., unweighted), each of which had a constant power spectrum density at frequencies ranging from 1.0 to 20 Hz. The order of the test stimuli was fully randomized, and each stimulus was repeated three times. Subjective scale for discomfort caused by whole-body vibration exposure was obtained for each direction by using the category judgment method. Also, the mean Stevens' power law exponent was obtained for females and males at each vibration direction. The power exponents for females were significantly higher than those for males under fore-and-aft and lateral WBV exposure. Subjective discomfort scales obtained under fore-and-aft and lateral vibration exposure exhibited significant gender differences: the upper limits of categories up to "4: uncomfortable" for females were observed to be higher than those for males while the upper limits of category "5: very uncomfortable" for females were lower than those for males. In contrast, no significant gender differences were observed in the subjective discomfort scale or in the power law exponent for vertical WBV exposure. Our results suggest that females are subjectively more sensitive than males for fore-and-aft and lateral WBV exposure, especially at higher vibration magnitude. Therefore, the differential effects in subjective responses to WBV in females and males should be taken into account in the ISO standard currently used in discomfort evaluation.