Professional heavy equipment vehicle operators suffer from a high prevalence of occupational injuries and illnesses. Among all injuries, fall-related injuries during vehicle ingress and egress have accounted for a large proportion of both fatal and non-fatal injuries in the US. The rate of these fall-related injuries has been much higher (up to 8 times) during egress as compared to ingress of vehicles. A likely cause for the disproportionally high fall-related injury rates during egress is a loss of postural stability. Prolonged exposure to Whole Body Vibration (WBV) compromises postural stability and thereby can increase the risks of falling. Off- road heavy equipment vehicle operators are particularly at a greater risk, because they are exposed to a higher level of WBV as compared to on-road vehicle operators. Furthermore, the predominant WBV exposure axis in off-road heavy equipment vehicles is not necessarily limited to the vertical (z-axis), but can often include significant fore-aft (x-axis) and/or lateral (y-axis) components. The nature of the additional impact of multi-axial WBV exposure on postural stability is poorly understood at present. Moreover, there is a lack of scientific studies to evaluate effective engineering interventions to mitigate multi-axial exposures during vehicle operation. We propose a repeated-measures laboratory study to identify the relative impacts of single- and multi- axial WBV exposure on postural stability, and to determine the effectiveness of a newly-invented innovative engineering control to mitigate multi-axial WBV exposure and associated postural instability. WBV exposures will be simulated in the laboratory by replicating actual field-measured vibration profiles from off-road heavy equipment vehicles on a motion platform. To determine whether multi-axial WBV exposure will have a greater impact on postural stability compared to vertical-dominant WBV, we will assess functional limits of stability, postural stability in standing balance, and anticipatory postural adjustments preceding functional tasks such as level gait and stair descent. We will also test whether the use of a multi-axial suspension seat will alleviate the adverse effects of multi-axial WBV on postural stability measures more effectively than a single-axial passive suspension seat. Results of this project can support future efforts to reduce the risks of fall-related injuries and therefore improve the occupational health and well-being for off-road vehicle operators. This project supports the NIOSH National Occupational Research Agenda, especially for the transportation and mining sectors, and the Musculoskeletal Health Research Priorities (NOT-OH-16-012), by clearly delineating the relative impacts of single- and multi-axial WBV exposures on postural stability among off-road vehicle operators, providing the neurophysiological underpinnings relating the type and extent of WBV with the risk of fall-related injuries, and by evaluating innovative engineering controls that may effectively reduce exposure to multi-axial WBV.
This project will determine if exposure to multi-axial whole body vibration (WBV) with significant lateral components will have additional impacts on postural stability as compared to vertical-dominant WBV; and whether the use of a multi-axial suspension seat (a new engineering intervention) will more effectively reduce overall WBV exposure and improve associated postural stability in comparison to a conventional single-axial passive suspension seat.