title: Effect of short-term exposure to whole body vibration in humans: relationship between wakefulness level and vibration frequencies.
abstract: The purpose of this study was to clarify the influence of different vibration frequencies on wakefulness level. Subjects were 7 healthy male university students aged 21.9+/-1.6 years (mean). All students were non-smokers. Three exposure conditions were used (10 Hz vibration, 20 Hz vibration, and no vibration). Whole-body vertical vibration was applied to subjects sitting on a car passenger seat using a whole-body vibration shaker (CV-300, Akashi) at a single frequency (10 or 20 Hz) at an acceleration level of 0.3 ms(-2) r.m.s. for 24 min. The objective wakefulness level based on EEGs was evaluated in terms of the alpha attenuation coefficient (AAC) obtained by the Alpha Attenuation Test (AAT). As parameters of psychological stress, salivary 3-methoxy-4-hydroxyphenylglycol (MHPG) and homovanillic acid (HVA) were used. The subjective wakefulness level was evaluated using a questionnaire based on the Kwansei Gakuin Sleepiness Scale (KSS), which is a scale developed for the Japanese based on the Stanford Sleepiness Scale (SSS). The KSS score, representing the subjective wakefulness level, decreased after the exposure irrespective of the exposure condition, but the decrease was not significant. The AAC, representing the objective wakefulness level, significantly decreased only after vibration exposure (10 Hz/20 Hz) but did not differ between the two vibration frequencies. No significant changes were observed after exposure to whole-body vibration in MHPG or HVA as parameters of vibration-related stress. The AAC decreased after exposure to whole-body vibration (10 Hz/20 Hz), suggesting a decrease in the wakefulness level. However, no differences were observed in the influence of the two different vibration frequencies test.
authors.affiliation: Department of Environmental Medicine, Kurume University School of Medicine, Asahi-machi, Kurume, Japan. yuka0503@med.kurume-u.ac.jp
authors.forename: Yuka
authors.initials: Y
authors.lastname: Satou
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Ishitake
authors.forename: Hideo
authors.initials: H
authors.lastname: Ando
authors.forename: Kaori
authors.initials: K
authors.lastname: Nagatomi
authors.forename: Michiko
authors.initials: M
authors.lastname: Hoshiko
authors.forename: Yoshiyasu
authors.initials: Y
authors.lastname: Tsuji
authors.forename: Hideki
authors.initials: H
authors.lastname: Tamaki
authors.forename: Akira
authors.initials: A
authors.lastname: Shigemoto
authors.forename: Midori
authors.initials: M
authors.lastname: Kusano
authors.forename: Mihoko
authors.initials: M
authors.lastname: Mori
authors.forename: Kunio
authors.initials: K
authors.lastname: Hara
mesh_terms: D000328:Adult; D004569:Electroencephalography; D006719:Homovanillic Acid / Q000032:analysis; D006801:Humans; D008297:Male; D008734:Methoxyhydroxyphenylglycol / Q000032:analysis; D012463:Saliva / Q000737:chemistry; D014732:Vibration; D014851:Wakefulness
chemical_list: D008734:Methoxyhydroxyphenylglycol; D006719:Homovanillic Acid