Regular articleAN UPDATED REVIEW OF EPIDEMIOLOGIC STUDIES ON THE RELATIONSHIP BETWEEN EXPOSURE TO WHOLE-BODY VIBRATION AND LOW BACK PAIN
Abstract
The aim of this paper is to update the information on the epidemiologic evidence of the adverse health effects of whole-body vibration (WBV) on the spinal system by means of a review of the epidemiologic studies published between 1986 and 1996. In a systematic search of epidemiologic studies of low back pain (LBP) disorders and occupations with exposure to WBV, 37 articles were retrieved. The quality of each study was evaluated according to criteria concerning the assessment of vibration exposure, assessment of health effects, and methodology. The epidemiologic studies reaching an adequate score on each of the above mentioned criteria, were included in the final review. A meta-analysis was also conducted in order to combine the results of independent epidemiologic studies. After applying the selection criteria, 16 articles reporting the occurrence of LBP disorders in 19 WBV-exposed occupational groups, reached a sufficient score. The study design was cross-sectional for 13 occupational groups, longitudinal for 5 groups and of case-control type for one group. The main reasons for the exclusion of studies were insufficient quantitative information on WBV exposure and the lack of control groups. The findings of the selected studies and the results of the meta-analysis of both cross-sectional and cohort studies showed that occupational exposure to WBV is associated with an increased risk of LBP, sciatic pain, and degenerative changes in the spinal system, including lumbar intervertebral disc disorders. Owing to the cross-sectional design of the majority of the reviewed studies, this epidemiologic evidence is not sufficient to outline a clear exposure–response relationship between WBV exposure and LBP disorders. Upon comparing the epidemiological studies included in this review with those conducted before 1986, it is concluded that research design and the quality of exposure and health effect data in the field of WBV have improved in the last decade.
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A finite element method study of the effect of vibration on the dynamic biomechanical response of the lumbar spine
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A validated finite element model of the lumbosacral spine was utilized. The model incorporated a 40 kg mass on the upper side and a 400 N follower preload. As a comparison, another model without a coupled mass was also employed. A sinusoidal acceleration with an amplitude of 1 m/s2 and a frequency of 5 Hz was applied to the upper and lower sides of the model respectively.
When the coupled mass point is not introduced: in the case of upper-side excitation, the lumbar spine shows a significantly larger response in the x-direction than in the z-direction, while in the case of lower-side excitation, the lumbar spine experiences rigid body displacement in the z-direction without any movement, deformation, rotation, or stress changes in the x-direction. When the coupled mass point is introduced: both upper and lower-side excitations result in significant differences in z-directional displacement, with relatively small differences in vertebral rotation angle, disc deformation, and stress. Under upper excitation, low-frequency oscillations occur in the x-direction. In both types of excitations, the anterior-posterior deformation of the L2-L3 and L4-L5 intervertebral discs is greater than the vertical deformation. The peak (maximum) disc stress exceeds the average stress and stress amplitude across the entire disc. Regardless of the excitation type, the stress distribution within the disc at the moment of peak displacement remains nearly identical, with the maximum stress consistently localized on the anterior side of the L4-L5 disc.
Accurately simulating lumbar spine biodynamics requires the inclusion of the upper body mass in the lumbosacral spine model. The physiological curvature of the lumbar spine could escalate the risk of lumbar spine vibration injuries. It is more instructive to apply local high stress in the disc as a lumbar spine vibration safety evaluation parameter.
Vibration reduction and energy harvesting of a human-seat-boat-water dynamic interaction system excited by waves
2023, Ocean EngineeringA vibration isolation means for a human-seat-boat-water dynamic interaction system subject to sea waves is proposed, for which to be numerically analyzed, the governing equations with numerical solution approaches are developed. The key idea is adopting electromagnetic isolators to replace often-used seat-damper to reduce vibrations by harvesting wave energy. The human body is modelled as a mass supported by a spring-damper connected to a seat, that through the electromagnetic isolator connected to a boat simplifying as a uniform beam-like vessel travelling in sea way. The wave force in the model is an approximate form commonly used in dynamic analysis of marine engineering, consisting of three components proportional to the relative motion of ship to the water, which adds additional mass, stiffness, and damping onto the ship. The parameters in the simulations are chosen from the practical designs or experimental/numerical reports. The simulation results reveal the effects of integrated interactions on the natural frequencies and dynamic responses of the ship subjected to short/long water waves and show very large reductions of human vibration level and effectively collecting wave energy. This confirms the proposed numerical model for ship vibration reduction and wave energy collection is attractive to simulate this complex integrated interaction system, and the proposed means based on electromagnetic isolators is no doubt to realize the aim of the paper. Some guidelines for designing this type of isolators are presented, which would be one of further develop directions for the global plan seeking/collecting green energies.
The objective of this study was to determine and compare the influence of osteoporosis on biomechanics of the spine after lumbar interbody fusion (LIF) surgery or non-fusion dynamic stabilization (NFDS) surgery under whole body vibration (WBV) which is typically present in moving vehicles.
Based on a previously validated finite element (FE) model of normal human lumbosacral spine, four surgical models including LIF, LIF with osteoporosis (LIF-OST), NFDS, and NFDS with osteoporosis (NFDS-OST) were constructed. Biomechanical responses of the surgical models to an axial cyclic load were calculated using transient dynamic analysis. Response parameters include vibration amplitudes of the endplate stress and screw stress at surgical L4–L5 level, vibration amplitudes of the disc bulge and intradiscal pressure at adjacent L3–L4 level.
Osteoporosis increased vibration amplitudes of all these investigated response parameters. Further, we found that vibration amplitudes of the endplate stress and screw stress for the LIF-OST model were significantly higher than those for the NFDS-OST model, but there was very small difference in vibration amplitudes of the disc bulge and intradiscal pressure between the LIF-OST and NFDS-OST models.
For both the LIF and NFDS surgeries, osteoporosis might increase the risk for implant failure and accelerate adjacent segment degeneration (ASD) under WBV. When osteoporosis occurs, LIF might be associated with a higher likelihood of implant failure at the surgical level compared with NFDS, and the surgical approach (LIF or NFDS) might have little influence on biomechanics of the adjacent level.
Whole-Body Vibration Exposure vis-à-vis Musculoskeletal Health Risk of Dumper Operators Compared to a Control Group in Coal Mines
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Measurements of WBV exposure were taken at the operator–seat interface using a human vibration analyzer for 110 dumper operators in three coal mines. This vibration measurement was supplemented by a questionnaire survey of 110 dumper operators exposed to WBV and an equal number of workers not exposed to WBV. The relative risk of musculoskeletal disorders (MSDs) has been assessed through the case-control study design.
ISO guidelines were used to compare the health risk. It was observed that the prevalence of pain in the lower back was 2.52 times more in the case group compared to the control group. The case group of Mine-2 was 2.0 times more prone to vibration hazards as compared to Mine-3.
The case group is more vulnerable to MSDs than the control group. The on-site measurement as well as the response of the dumper operators during the questionnaire survey corroborates this finding.
Effect of Whole-Body Vibration Exposure in Vehicles on Static Standing Balance after Riding
2023, VibrationApplication of neural network in prediction of frequency response of drivers during driving
2023, Proceedings - 2023 IEEE 23rd International Conference on Bioinformatics and Bioengineering, BIBE 2023