Factors affecting operator exposure to whole-body vibration

Authors: Wesley Killen and Tammy Eger

Factors affecting operator exposure to whole-body vibration (PDF)

Motorized vehicle operators can be exposed to whole-body vibration (WBV) levels associated with increased risk for low-back problems, neck problems, and muscle fatigue2,4,5. Reducing exposure to WBV can be accomplished through control strategies targeting machine, environment, and operator factors.

Vehicle factors:
Vehicles that are older or poorly maintained have been found to produce greater levels of WBV6. Regular maintenance of the engine, suspension, and tire pressure is required to minimize WBV. Seat selection is also critical. Several researchers have shown that seats can amplify vibration if the correct seat is not paired with the right vehicle7,13. Seats are capable of minimizing WBV exposure1,15; however, it can be difficult for the vehicle purchaser to know which seat is the “best”, and it should not be automatically assumed that the newest suspension seats will be optimal7,15.  Purchasers are encouraged to ask the vehicle manufacturer for information on the vibration attenuation capabilities of the seat, and whether the seat was tested within the work conditions that the purchaser intends to use the vehicle and seat.

Environmental factors:
Driving surfaces should be properly maintained to remain as smooth as possible7,11. Rough terrain is most problematic at increased operating speeds6, 7. In addition to general roughness, the safety standards8,9 are clear that significant jolts or bumps may be particularly detrimental to operator health and safety. Regular inspection is recommended to report roadway problems that require repair.  Floor surfaces and docking plates in warehouses should also be maintained to prevent jolts, and impacts.

Operator factors:
Sitting for prolonged periods of time is associated with increased risk for LBP10. LBP risk is increased further when workers are exposed to WBV4, and further still when workers are exposed to WBV with the back in a non-neutral posture (flexed forward; twisted; lateral bend)3, 4. LBP risk can be reduced if the vehicle cab and seat offer enough adjustability for the driver to maintain a neutral driving posture2,3. Training should be provided for each vehicle/seat combination so drivers know how the seat can be adjusted to suit their body dimensions and weight.  Furthermore, it is important that seats are adjusted according to manufacturer specifications, typically midway in its vertical travel when the operator is seated, in order to avoid end-stops.  Workers should also be encouraged to make small modifications to their sitting posture throughout a shift. Lastly, workers should take a few minutes to walk when they first exit a vehicle before performing any lifting or heavy physical work14.
Posture is also important for vehicles that are operated from a standing position. Vibration will be transmitted up through the body to a much greater extent if the operator assumes a stiff, straight-legged stance15. Therefore, operators should assume a relaxed posture with knees slightly flexed during operation.

Motorized vehicle operators can be exposed to whole-body vibration (WBV) levels associated with increased risk for low-back problems, neck problems, and muscle fatigue2,4,5. Reducing exposure to WBV can be accomplished through control strategies targeting machine, environment, and operator factors.

Vehicle Factors:
Vehicles that are older or poorly maintained have been found to produce greater levels of WBV6. Regular maintenance of the engine, suspension, and tire pressure is required to minimize WBV. Seat selection is also critical. Several researchers have shown that seats can amplify vibration if the correct seat is not paired with the right vehicle7,12. Seats are capable of minimizing WBV exposure1,16; however, it can be difficult for the vehicle purchaser to know which seat is the “best”, and it should not be automatically assumed that the newest suspension seats will be optimal7, 16.  Purchasers are encouraged to ask the vehicle manufacturer for information on the vibration attenuation capabilities of the seat, and whether the seat was tested within the work conditions that the purchaser intends to use the vehicle and seat.

Environmental Factors:
Driving surfaces should be properly maintained to remain as smooth as possible7,11. Rough terrain is most problematic at increased operating speeds6, 7. In addition to general roughness, the safety standards8,9 are clear that significant jolts or bumps may be particularly detrimental to operator health and safety. Regular inspection is recommended to report roadway problems that require repair.  Floor surfaces and docking plates in warehouses should also be maintained to prevent jolts, and impacts.

Operator Factors:
Sitting for prolonged periods of time is associated with increased risk for LBP10. LBP risk is increased further when workers are exposed to WBV4, and further still when workers are exposed to WBV with the back in a non-neutral posture (flexed forward; twisted; lateral bend)3, 4. LBP risk can be reduced if the vehicle cab and seat offer enough adjustability for the driver to maintain a neutral driving posture2,3. Training should be provided for each vehicle/seat combination so drivers know how the seat can be adjusted to suit their body dimensions and weight.  Furthermore, it is important that seats are adjusted according to manufacturer specifications, typically midway in its vertical travel when the operator is seated, in order to avoid end-stops.  Workers should also be encouraged to make small modifications to their sitting posture throughout a shift. Lastly, workers should take a few minutes to walk when they first exit a vehicle before performing any lifting or heavy physical work13.
Posture is also important for vehicles that are operated from a standing position. Vibration will be transmitted up through the body to a much greater extent if the operator assumes a stiff, straight-legged stance14. Therefore, operators should assume a relaxed posture with knees slightly flexed during operation.

Driver training programs should also review the importance of reporting vehicle and road maintenance problems.  Drivers should be encouraged to follow posted driving speeds and where feasible reduce speeds in areas with rough road or floor conditions.  Driving speeds should also be lowered when mobile equipment designed to carry large loads (e.g. Haulage truck) are empty, as WBV exposure is increased when driven empty7.

Conclusion

Motorized vehicle operators are at risk for low-back and neck disorders from daily exposure to WBV.  The following control strategies are recommended to mitigate injury risk:

  • Remove the worker from the vibration source
  • Purchase equipment with lower vibration emissions and adjustable seating
  • Install suspension and seating suited to the conditions
  • Maintain equipment and roadways
  • Reduce driving speed
  • Maintain a neutral driving posture
  • Reduce consecutive hours of exposure to WBV
  • Avoid lifting or heavy physical work immediately following exposure to WBV
  • Avoid driving over rough terrain if possible, and/or slow driving speeds over rough roads and floor surfaces

Key messages

  • Evidence continues to support the association between prolonged whole-body vibration exposure and an increased risk for lower-back disorders in motorized-vehicle operators.
  • Seat performance, road conditions, and driving speeds influence whole-body vibration exposure.
  • The first line of prevention is purchasers consulting with manufacturers to select equipment with the lowest vibration emission values based on proper seat installation and suspension systems.
  • Best practices to limit a worker’s risk of developing a low-back disorder include: purchase vehicles with lower vibration exposure emissions; maintain vehicles and roadways; consider a reduction in operating speeds where feasible; maintain a neutral trunk and neck posture, with the back supported when driving; avoid lifting or heavy physical work immediately after driving and consider a reduction in daily driving time.

Implications for the prevention of MSD

Long term exposure to whole-body vibration puts workers at an increased risk for low-back and neck disorders. The hierarchy of controls should be followed to mitigate injury risk.  Equipment with lower vibration emissions should be purchased, vehicles and roadways should be maintained, lower driving speeds should be considered, neutral driving postures should be adopted, and heavy physical work should be avoided immediately after exposure to WBV.

References

  1. Blood, R.P., Ploger, J.D., Yost, M.G., Ching, R.P., and Johnson, P.W. (2010). Whole body vibration exposures in metropolitan bus drivers: A comparison of three seats. Journal of Sound and Vibration, 329, 109-120.
  2. Boshuizen, H.C., Bongers, P.M. & Hulshof, C.T.J. (1990). Self-reported back pain in tractor drivers exposed to whole-body vibration. International Archives of Occupational and Environmental Health, 62, 109-115.
  3. Bovenzi, M., Pinto, I., and Stacchini, N. (2002) Low back pain in port machinery operators. Journal of Sound and Vibration, 253(1), 3-20.
  4. Bovenzi, M., Schust, M., Menzel, G., Prodi, A., & Mauro, M. (2015). Relationships of low back outcomes to internal spinal load: a prospective cohort study of professional drivers. International archives of occupational and environmental health, 88(4), 487-499.
  5. Burström, L., Nilsson, T., & Wahlström, J. (2015). Whole-body vibration and the risk of low back pain and sciatica: a systematic review and meta-analysis. International archives of occupational and environmental health, 88(4), 403-418.
  6. Cann, A.P., Salmoni, A.W. & Eger, T.R. (2004). Predictors of whole-body vibration exposure experienced by highway transport truck operators. Ergonomics, 47(13), 1432-1453.
  7. Eger, T.R., Contratto, M.S., and Dickey, J.P. (2011). Influence of driving speed, terrain, seat performance and ride control on predicted health risk based on ISO 2631-1 and EU Directive 2002/44/EC. Journal of Low Frequency Noise, Vibration, and Active Control, 30(4), 291-312.
  8. International Standards Organization (ISO): Evaluation of Human Exposure to Whole-Body Vibration, (ISO 2631-1), Geneva, 1997.
  9. International Standards Organization (ISO): Mechanical vibration and shock – Evaluation of human exposure to WBV. Part 5: Method for evaluation of vibration containing multiple shocks, (ISO 2631-5), Geneva, 2004.
  10. Lis, A. M., Black, K. M., Korn, H., & Nordin, M. (2007). Association between sitting and occupational LBP. European Spine Journal, 16(2), 283-298.
  11. Motmans, R. (2012). Reducing whole body vibration in forklift drivers. Work, 41(Supplement 1), 2476-2481.
  12. Paddan, G. S., & Griffin, M. J. (2002). Effect of seating on exposures to whole-body vibration in vehicles. Journal of Sound and Vibration, 253(1), 215-241.
  13. Palmer, K. T., Griffin, M. J., Syddall, H. E., Pannett, B., Cooper, C., & Coggon, D. (2003). The relative importance of whole body vibration and occupational lifting as risk factors for low-back pain. Occupational and Environmental Medicine, 60(10), 715-721.
  14. Pel, J.J.M., Bagheri, J., van Dam, L.M., vanden Berg-Emons, H.J.G., Horemans, H.L.D., Stam, H.J., & vander Steen, J. (2009). Platform accelerations of three different whole-body vibration devices and the transmission of vertical vibrations to the lower limbs. Medical Engineering & Physics. 31(8), 937-944.
  15. Xiaoxu, J., Eger, T., & Dickey, J. (2015) Development of a seat selection algorithm to match industrial seats with specific forestry vibration exposures. International Journal of Forest Engineering. 26:1, 48-59.

Last updated: 2016

Disclaimer: Position papers are funded by the Centre of Research Expertise for the Prevention of Musculoskeletal Disorders, which receives funding through a grant provided by the Ontario Ministry of Labour. The views expressed are those of the authors and do not necessarily reflect those of the Centre nor of the Province.