Absorption of energy during vertical whole-body vibration exposure.
Absorbed power (PAbs) during exposure to vertical whole-body vibration in a sitting posture was measured on 15 male and 15 female subjects. Different experimental conditions were applied, such as vibration level (0.5-1.4 m s(-2)) and frequency (2-100 Hz), body weight (54-93 kg) and, relaxed and erected upper body positions. Results show that PAbs was strongly related to the frequency of the vibration, peaking within the range of 4-6 Hz. The peak was predominantly located in the lower end of this range for females and for the relaxed sitting position. PAbs increased with acceleration level and body weight. Almost a ten-fold increase in PAbs was observed at the critical frequency when the vibration exposure was raised from 0.5 to 1.4 m s(-2). If risk assessment is based on the assumption that the amount of PAbs, independent of the frequency of the vibration, indicates a hazard, then the ISO-standard 2631 under- and overestimates the risk at frequencies below and above about 6 Hz, respectively. The results also indicate a need for differentiated guidelines for females and males. Many types of vehicles produce whole-body vibration with frequencies which coincide with the range where the highest PAbs was observed. PAbs is a 'new' concept for measurement of whole-body vibration exposure. Although not yet thoroughly evaluated, this measure may be a better quantity for risk assessment than those specified in ISO 2631 since it also takes the dynamic force applied to the human body into account.
Lundström
R
R
Department of Technical Hygiene, National Institute for Working Life, Umeå, Sweden. Ronnie.Lundstrom@niwl.se
Holmlund
P
P
Lindberg
L
L
D000042:Absorption / Q000502:physiology; D000054:Acceleration; D000328:Adult; D001835:Body Weight / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D011187:Posture / Q000502:physiology; D012044:Regression Analysis; D014732:Vibration