No abstract

The relevant literature on the long-term effects of whole-body vibration (wbv) was analyzed in order to obtain condensed information concerning a possibly higher health risk due to long-term exposure, the relationships between the quality of exposure (intensity, duration, frequency) and pathological effects, the significance of individual factors, conclusions for standard setting, and medical health care of workers exposed to wbv. Vibration exposure was characterized by measured values in one third of papers, whereas more than 30% of the publications selected did not contain any exposure data. Health data of about 43 000 workers exposed to wbv and 24 000 persons in control groups were reported. The results indicate an increased health risk of the spine and of the peripheral nervous system after intense long-term wbv. With a lower probability, the digestive system, the peripheral veins, the female reproductive organs, and the vestibular system were also affected. Long-term effects on other organs cannot be precluded. Wbv can worsen certain endogenous conditions. Specific diagnostic features of pathological changes induced by wbv with frequencies below 20 Hz do not exist. On average, the health risk increases with higher intensity or duration of exposure, however, quantitative exposure-effect relationships cannot be derived at present. Since wbv near the Exposure Limit of the International Standard IS 2631 is not completely safe, this survey provides arguments in favour of a lower limit. Contra-indications for professional exposure to wbv and further research needs are discussed.

The problem of a "vibration disease" caused by low-frequency whole-body vibration (wbv) is critically discussed. Disorders of the nervous, circulatory, and digestive systems are interpreted not to be predominantly wbv-specific, but to be related to the totality of working conditions. Long-term wbv exposure can probably contribute to the pathogenesis of disorders of female reproductive organs (menstrual disturbances, anomalies of position) and disturbances of pregnancy (abortions, stillbirths). Animal experiments suggest harmful effects on the fetus. WBV has a minor synergistic effect on the development of noise-induced hearing loss. Degenerative changes of the spine are more prevalent among wbv-exposed workers. Model calculations demonstrate an increased spinal load in pregnant women exposed to wbv or self-induced vibration, and illustrate a possibility for the comparison of data on stress, strain, and strength. The analysis of individual exposure-effect relationships is suggested as a future approach for evaluating potential occupation-related diseases.

A conceptual framework provides the possibility to identify factors determining the effects of whole-body vibration (WBV) on the spine and the internal stress-strain relationships. Epidemiological studies were critically evaluated with respect to their significance for the derivation of quantitative exposure-effect relationships. The approach of deriving such relationships from a comparison with self-generated accelerations during daily activities was considered as unsuited. Trunk muscle activity and control with apparently identical accelerations of body parts during selfgenerated and forced motions differ widely. Simple biodynamic models coupled with experimental in vivo and in vitro data permitted a preliminary deduction of quantitative relationships between WBV and spinal health with the consideration of individual factors and exposure conditions. Examples of anatomy-based verified finite element models and their application are provided. Such models are considered as a very promising instrument. They can be used to assess quantitatively preventive measures and design. Future research needs concern the examination of (1) the nonlinearity of biodynamics, (2) the effects of WBV in x-and y-axes, (3) the strength of the spine for shear, (4) the contact parameters between the seat and man, (5) the significance of postures and muscle activity, and (6) material properties of spinal structures.

: This experimental study aimed at acquiring detailed data about the human transmission behaviour as a basis for an improved estimation of the strain, induced by whole body vibration (wbv). Four male subjects were exposed to vertical sinusoidal wbv (2-12 Hz 1.5 and 3.0 ms-2 RMS).The steady state force response was measured at the input interface, and accelerations were registered at the seat, head, shoulder, and upper trunk. Transmissibilities and apparent mass as quotients of RMS-values were determined. In addition, the corresponding quotients of peak values, as well as their accompanying phase angles were calculated separately for maximum acceleration or minimal acceleration, and for the extreme values of apparent mass in relation to the body mass.