Summary
Background: There is a high prevalence of injury and low back pain prevalence associated with professional drivers, including mobile police officers. In particular, the reduction in lumbar lordosis has been hypothesized as a contributing risk factor for injury during prolonged seated periods. Furthermore, the use of the mobile data terminal (MDT) and the protective equipment worn by officers creates a unique interface between the occupant and the car seat. Purpose: To evaluate a novel thoracic support that was designed to address the unique seated working demands of mobile police officers. Methods: Fourteen participants: 7 male (21.3 (1.9) years, 1.71 (0.06) m, 75.1 (9.3) kg) and 7 female (23.3 (4.4) years, 1.69 (0.06) m, 68.2 (7.7) kg) were recruited from a university student population. Participants attended two 120 minute driving simulations on separate days; using a standard Crown Victoria Interceptor seat and the same seat equipped with a retrofitted surface mounted thoracic support. Time-varying spine postures, seat pressure measures and perceived discomfort were measured. Results: The introduction of a thoracic support changed postures, reduced lower seat back interface pressures but did not reduce discomfort compared to a standard seat during a 2 hour exposure period. Average discomfort scores were low with all values below 10mm out of a possible 100mm for both seating conditions. Discomfort was found to have small increases over time in the neck and right thigh with the support, but mean values remained low (under 3mm). Lumbar angles became more flexed with the support compared to a standard seat. Posterior pelvic rotation was reduced in female participants while in males there was greater posterior pelvic rotation with the support. There was a reduction in interface pressures on the bottom half of the seat back, the area where the duty belt is in contact with the seat. Conclusions: The postural and seat interface information support further field evaluations using a retrofitted thoracic insert as an in-vehicle ergonomic intervention for police officers. Further investigations focused on prolonged exposure to the intervention will guide future design iterations.