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Abstract
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OBJECTIVES
Although musculoskeletal disorders of the low back have been linked to excessive whole body vibration during vehicle use, there is a need to explore head/neck vibration in occupational environments. Resonant frequencies may amplify vibration transmitted to the head/neck and increase risk of musculoskeletal disorders.
Methods
An observational fieldwork study directly measuring vibration exposure at the seat and head of 10 rural workers operating quad bikes over farm terrain for ∼30 min.
Results
Vertical axis root-mean-squared acceleration was higher at the head/neck compared to the seat. Mean spectral coherence was strong (>0.8) in the vertical axis from 1.3 to 4.9 Hz, indicating a strong relationship between vertical vibrations measured at the seat and the head. Power spectral densities demonstrated system amplification, with mean and peak seat-to-head transfer functions of 1.44 (95% CI ± 0.08) and 1.66 (±0.14), respectively, from 1.3 to 4.9 Hz. There was also a peak phase lag of −66.5° (±13.9°) at 4.9 Hz for head relative to seat measured vertical vibration, which may increase compressive loads of the cervical spine.
Conclusions
While it is unknown whether these amplified and out-of-phase vibrations measured at the head/neck increase the risk of musculoskeletal disorder, the current biodynamic response to vibration exposure may help explain previously reported high prevalence of neck pain in farmers that use quad bikes. Our future laboratory based studies will aim to validate these fieldwork seat and head data and explore the effect of such vibration transmission on spinal biomechanical models as well as on proprioceptive and perceptual pathways that may also relate to injury.
Language: en |