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An experiment was engaged in to explore the mechanism that may cause disruption of manual control performance during vibration exposure. The experiment was conducted in which 8 subjects performed three simple tasks in static conditions and during exposure to whole-body vertical (Z-axis) vibration at 0.5 and 4.0 Hz, at an acceleration magnitude of 2.1 meters per square second r.m.s. Vibrations of 0.5 and 4.0 Hz caused marked increase in control activity at frequencies of up to about 1 Hz compared to the condition without vibration.

Analysis of the transmission of roll and pitch seat vibration to the head in seated subjects revealed that the head moved in the pitch, vertical and fore-and-aft axes when the subject experienced pitch seat vibrations and in the roll, lateral and yaw axes when the subject experienced roll seat vibrations. Subjects' head motion was less when their backs were not in contact with the backrest than when their backs rested against the backrest. Alteration of the position of center of rotation along different axes affected head motion in different planes.

An experimental comparison of vibrotactile thresholds on the finger in nine male subjects using two alternative systems, where one supports push force, contact force and the surround, which are absent in the other system, reveals that vibrotactile threshold estimations should include the vibrational frequency, area of vibrational contact, the condition of the contact region, contact force, push force, finger temperature and the waveform distortion. The method with controlled push force, contact force and surround offers greater repeatability in the estimation of vibrotactile thresholds.

The effects of vibration on the ability to accomplish tasks were studied. Performance declined as a function of exposure time to vibration but did not negatively weigh on accomplishment of performance. Subjects tend to respond to perceived movements more slowly because of fatigue and reduced motivation over time. Fourteen healthy, right-handed male volunteers from the student and faculty body of University of Southampton participated in the study for five days in 1990.