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 [S_ed(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 S_ed(8) WBV exposure measures were not different between the two seat groups [VDV(8), P = 0.33; 0.35 (−0.32, 1.03); S_ed(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 S_ed(8)].