A Randomized Controlled Trial of a Truck Seat Intervention: Part 1—Assessment of Whole Body Vibration Exposures

Abstract

Full-time vehicle and heavy equipment operators often have a high prevalence of musculoskeletal disorders, especially low back pain (LBP). In occupations requiring vehicles or heavy equipment operation, exposure to whole body vibration (WBV) has been consistently associated with LBP. LBP is the most common cause of work-related disability and continues to be the leading cause of morbidity and lost productivity in the US workforce. Using a parallel randomized controlled trial design, over a 12-month period, this study evaluated two different seating interventions designed to reduce WBV exposures. Forty professional truck drivers were initially recruited and randomly assigned to one of two groups: (i) a passive suspension/control group-20 drivers who received a new, industry-standard air-suspension seat, and (ii) an intervention group-20 drivers who received an active-suspension seat, which has been shown to reduce vertical WBV exposures by up to 50% compared to passive seats. WBV exposures from the truck seat and floor were collected during driver's full shifts (6-18 h) before (pre-intervention) and after the intervention (0, 3, 6, and 12 months post-intervention) per International Standards Organization (ISO) 2631-1 and 2631-5 WBV standards. After subject dropout and turnover, 16 truck drivers remained in each group. The pre-intervention WBV data showed that there were no differences in the daily equivalent time-weighted average WBV exposures [A(8)], vibration dose values [VDV(8)], and static spinal compression doses [Sed(8)] between the two groups (P's > 0.36). After the new seats were installed, the A(8) values showed that the active suspension/intervention group experienced much greater reduction in the vertical (z) axis [~50%; P = <0.0001; Cohen's d effect size (95% CI) = 1.80 (1.12, 2.48)] exposures when compared to in the passive suspension/control group [~20%; P = 0.23; 0.33 (-0.36, 1.02)]. The post-intervention z-axis VDV(8) and Sed(8) WBV exposure measures were not different between the two seat groups [VDV(8), P = 0.33; 0.35 (-0.32, 1.03); Sed(8), P = 0.61; 0.08 (-0.59, 0.76)]. These study findings indicate that, relative to the current industry-standard, passive air-suspension seats which are ubiquitous in all semi-trucks today, the active suspension seat dramatically reduced average continuous [A(8)] WBV exposures but not periodic, cumulative impulsive exposures [VDV(8) and Sed(8)].

Health effects associated with occupational exposure to hand-arm or whole body vibration

“…The published computational models are consistent with data collected in humans showing that the resonant frequency of the human body is between 5–10 Hz (Zeeman et al 2015; Matsumoto,Griffin 2002; Qiu,Griffin 2010; Basri,Griffin 2011), and that the resonant frequency of the human hand-arm system is between 100–300 Hz depending on the location of the measurement (Dong, Welcome, et al 2004; Dong, Welcome,Wu 2005; Dong et al 2006; Wu et al 2007; Wu et al 2008). These models, along with experimental data collected in human and animal subjects have helped predict how various interventions may reduce the transmission of vibration from a vehicle or tool to the body (Krajnak et al 2015; Hewitt et al 2015; Md Rezali,Griffin 2016; Welcome et al 2016; Md Rezali,Griffin 2017; Basri,Griffin 2014; Qiu,Griffin 2012; Jonsson et al 2015; Beard,Griffin 2013; Ji, Eger,Dickey 2017; Du et al 2018; Johnson et al 2018).…”

“…Because many patients seen for back pain do not have injuries to their spine or disks, which are can be detected using imaging methods, understanding the contribution of soft tissue injury (i.e., skeletal muscle, tendons, ligaments) to the incidence of back pain is critical for identifying interventions that will prevent injuries (Du et al 2018; Bovenzi et al 2015; Bovenzi 2010; Palmer et al 2003; Bovenzi 1996; Bovenzi,Zadini 1992). Data collected in humans, have been used to alter seat design to reduce vibration transmission and improve comfort in vehicles (Qiu,Griffin 2012; Beard,Griffin 2013; Basri,Griffin 2014; Jonsson et al 2015; Ji, Eger,Dickey 2017; Du et al 2018; Johnson et al 2018). Mental fatigue and stress can also exacerbate pain, therefore, taking breaks to stretch and help maintain mental alertness may also improve pain perception (Yung et al 2017; Tachi et al 2004).…”

Comparison of Whole-Body Vibration Exposures When Operating a City Bus with an Active, Passive and Static Suspension Bus Seat

“…This is the first time an active suspension seat, designed for use in semitrucks, was installed and evaluated in a municipal bus. Similar to the active suspension seat's performance in semitrucks (Johnson et al, 2018), the active suspension bus seat substantially reduced WBV exposures below what is achievable with the industry-standard, passive air suspension seat. On city streets and freeways, the active suspension seat WBV exposures were 40 to 60% lower than the exposures measured with the industry-standard passive, air-suspension seats.…”

“…In summary, just as in semitrucks, the active suspension seat reduced the bus drivers WBV exposures by 40% to 60%; this is a substantial reduction in exposure and extremely effective for a relatively low-cost engineering control (relative to the cost of modifying the bus cab or bus suspension). A recent randomized controlled trial comparing WBV exposures and self-reported low back pain (LBP) between a group of truck drivers that received active suspension seats and a second group that received new passive, air suspension seats, demonstrated that truck drivers that received active suspension seats not only experienced a 50% reduction in their WBV exposures but also experienced a clinically meaningful 30% reduction in self-reported low back pain (LBP), whereas a 15% reduction in WBV exposures (Johnson et al, 2018) and no change in LBP was reported in the drivers that received the passive air suspension seats (Kim et al, 2018).…”

Effects of Multi-axial Whole Body Vibration Exposure on Postural Stability

“…Each participant was exposed to 4 hours of WBV with a 30-minute break in the middle, in three different experimental conditions: multiaxial, vertical-dominant, and no WBV exposure (control condition). To create vertical-dominant and multi-axial WBV exposures in a laboratory setting, actual field-measured tri-axial floor vibration profiles, collected from long-haul trucks and various mining vehicles (Johnson, Zigman, Ibbotson, Dennerlein, & Kim, 2018;J. H. Kim, Marin, & Dennerlein, 2018), were played onto a 6-degree-of-freedom motion platform.…”