Whole-body vibration

Whole-body vibration is not relevant to this book. 

Iritton, J. C, Rubin, C. T., Qin, Y, and McLeod, K. J. (1997). Whole Body Vibration in the Skeleton Development of a Resonance-Based Testing Device, Annals of Biomedical Engineering, 25 831-839. 

Frequency Weighting. The inverse frequency contour (i.e., reciprocal) to an equinoxious contour should be applied to a stimulus containing many frequencies to produce an overall magnitude that appropriately combines the contributions from each fr uency. The frequency weightings most commonly employed for whole-body and hand-transmitted vibration are shown in Fig. 10.1 (ISO 2631-1,1997 ISO 5349-1, 2001). The range of frequencies is from 1 to 80 Hz for whole-body vibration, and from 8 to 1250 Hz for vibration entering the hand. A frequency weighting for shocks may also be derived from a biodynamic model (see Dynamic Response Index (DRI) in Sec. 10.3.1). 

A second function, used for exposure to whole-body vibration, is the vibration dose value, VDV, for which F aJ,t)) = ajf) and m = r = 4. The function is thus ... 

Chronic exposure to whole-body vibration may result in an increased risk of low back pain, sciatic pain, and prolapsed or herniated lumbar disks compared to control groups not exposed to vibration. These injuries occur predominantly in crane operators, tractor drivers, and drivers in the transportation industry (Bovenzi and Hulshof, 1998). However, it is difficult to differentiate between the roles of whole-body vibration and ergonomic risk factors, such as posture, in the development of these disorders. 

Ityury from Shock and Impact. Physiological responses to shocks and objects impacting the body include those discussed for whole-body vibration. For small contact areas, the injuries are often related to the elastic and tensile limits of tissue (Haut, 1993 von Gierke et al., 2002). The respcmses are critically dependent on the magnitude, direction, and time history of the acceleration and forces entering the body, the posture, and on the nature of any body supports or restraints (e.g., seat belt or helmet). 

Vibration Perception. The perception of vibration depends on the body site and on the stimulus firequency. The thresholds in Table 10.2 are typical of those for healthy adults, and are expressed as instantaneous RMS accelerations (i.e., with T 1 s in Eq. (10.2)). The value for whole-body vibration is given in terms of a frequency-weighted acceleration, and so is applicable to vibration at frequencies from 1 to 80 Hz. The values for hand-transmitted vibration are for sinusoidal stimuli applied to the fingertips of males (M) and females (F) at the specified frequencies. 

The assessment of whole-body vibration onploys the VDV averaged over 8 hours [i.e., T = 28,800 s in Eq. (10.6)], with fiequency weighting for vertical vibration and frequency weighting Wj for horizontal vibration. It is believed that the higher-power metrics, as recommended here, better represent the hazard presented by motion containing transient events, particularly when these become small-magnitude shocks or impacts. The most appropriate metric, however, remains a subject for research. 

Vibration Isolation. Excessive whole-body vibration is most commonly encountered in transportation systems, where it predominandy affects seated persons. In consequence, an effective rem ial measure is to reduce the vertical component of vitHation transmitted through seats (and, where... 

Vibration-Isolated Tool Handles. Vibration isolation systems have been applied to a range of powered hand tools, often with dramatic consequences. For example, the introduction of vibration-isolated handles to gasoline-powered chain saws has significantly reduced the incidence of HA VS among professional saw operators. Unfortunately, such systems are not provided for the handles of all consumer-grade chain saws. The principle is the same as that describe for whole-body vibration isolation, but in this case the angular resonance frequency can be 350 rad/s (i.e.,/o 55 Hz) and still effectively reduce chain-saw vibration. The higher resonance frequency results in a static deflection of the saw tip relative to the handles that, with skill, does not impede the utility of the tool. 

Bovenzi, M., and C. T. J. Hulshof An Updated Review of Epidemioiogic Studies of the Relationship Between Exposure to Whole-Body Vibration and Low back Pain, J. Sound Vib., 215 595 (1998). 

ISO 2631 -1, Mechanical Vibration and Shock—Evaluation of Human Exposure to Whole Body Vibration—Part I General Requirements, 2d ed.. International Organization for Standardization, Geneva, 1997. 

The ride and comfort improvements in modem tmcks should have reduced these problems. However, with the improved ride drivers now tend to try to spend more consecutive horns behind the wheel, exposing themselves to longer continuous periods of whole body vibration. The vibration is less, but longer continuous exposure may be offsetting the gains. 

Exposure of the whole body to vibration (usually through the feet/buttocks when riding in a vehicle). Whole body vibration may increase the risk for injury, including low back pain and internal organ disruption. See also Ergonomics Segmental Vibration (Hand-Arm Vibration). 

Riding on machines and vehicles can create whole body vibrations and injuries. Designs for suspensions and seating may reduce the potential for such injuries." ... 

Studies on whole body vibration suggest that truck drivers, tractor drivers, and heavy equipment operators have a greater incidence of back troubles than do people in other kinds of jobs. Drivers of such vehicles experience low frequency vibration in the 4-8 Hz range while seated. Spinal compression, length of exposure, and other factors may contribute to damage. Other factors may also contribute. 

For several decades, the International Organization for Standardization (ISO) published several standards for shock and vibration of equipment. ISO also published standards for human exposure to mechanical vibration and shock. One standard addresses hand-arm vibration syndrome (HAV). Another addresses whole-body vibration (WBV). 

Figure 23-8. Health risks from whole body vibrations from vehicles. Refer to the source for additional implementing details. (FromMIL-STD- 1472G)...

ISO 5349, Mechanical Vibration Measurement and Assessment of Human Exposure to Hand-Transmitted Vibration, International Standards Organization, Geneva. ISO 2631, Guide for the Evaluation of Human Exposure to Whole-Body Vibration, ISO, Geneva. 

Individuals subject to whole-body vibration have experienced visual problems vertebral degeneration breathing problems motion sickness pains in the abdomen, chest, and jaw backache joint problems muscle strain and problems with their speech. Although there are still many questions regarding vibration, it is definite that physical problems can transpire from exposure to vibration. 

These Regulations are designed to protect persons from the risk to their health and safety of the effects of exposure to vibration. There are two types of vibration, hand-arm vibration (HAV) and whole-body vibration. Regular and frequent exposure to HAV can lead to permanent health effects. This is most likely when contact with a vibrating tool or work process is a regular part of a person s job. Too much exposure to HAV can cause hand-arm vibration syndrome (HAVS) and carpal tunnel syndrome (CTS). HAVS affects the nerves, blood vessels, muscles and joints of the hand, wrist and arm. Carpal tunnel syndrome is a nerve disorder which may involve pain, tingling, numbness and weakness in parts of the hand. 

Whole-body vibration, particularly when combined with poor postures... 

Whole body vibration levels must be minimized. Critical whole body resonance frequencies are between 2-200 Hz. 

Ergonomic design problems and whole-body vibration... 

Some of the hazards associated with this vehicle are collisions with pedestrians, other vehicles or structures, such as scaffolding. They can be struck by falling materials and tools or be overloaded. The person driving the truck can be thrown from the vehicle, come into contact with moving parts on the truck, suffer the effects of whole body vibrations due to driving over potholes in the roadway and suffer from the effects of noise and dust. 

Table 17.2 Machines which could produce significant whole-body vibrations...

The Control of Vibration at Work Regulations introduce, for both hand-arm and whole-body vibrations, a daily exposure limit and action values. These values are as follows ... 

The Regulations require that where there is a likelihood of WBV, the employer must undertake a risk assessment. The HSE Guidance document, L141, gives detailed advice to help with this risk assessment and on estimating daily exposure levels. Whole-body vibrations risks are low for exposures around the action value and usually only simple control measures are necessary. 

Do machines comply with maximum permitted levels of whole-body vibration exposure levels ... 

For work equipment first provided to employees for use prior to 6 July 2007 and where compliances with the exposure limit values is not possible, employers have until 2010 to comply and, in the case of agriculture and forestry, 2014 (for whole body vibration). 

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