Low back injuries and driving postures in lift truck operators

Musculoskeletal disorders in the workplace continue to plague many organizations. Lift Truck (LT) operators are at an increased risk for low back injuries (LBP). Limited studies have analyzed driving postures and the risk of LBP during the normal operation of a LT. This study will quantify spinal loading along with the risk of developing a low back injury associated with operating a LT. A six station LT rodeo was constructed that simulated normal operating tasks. Two LT models, each from a different manufacturer, were used and five subjects (one female, four males) were recruited to drive each LT model. Four digital video cameras were attached to a roof mount on the LTs to capture operator postures during the driving tasks. Three stations were selected and collapsed into two tasks for analysis in this study. The two tasks were the operation of a narrow passage and the combined simulated rail car and pylon manoeuvrability task. 3D-Match, a posture matching program that estimates spinal loading values, was used to analyze the time spent in neutral, mild and severe postures and to estimate kinetic load at the lumbar spine. Spinal variables such as peak and cumulative spinal loading, shear loading, and moments were calculated. 58% of operating time was spent in axial twisting postures during a static work task while 27% of time was spent axial twisting during a dynamic work task. Peak compressive forces of 2863 N and shear loading of 368 N were below injury thresholds. Results showed that the more complex a task was, the greater the loading on the spine became. Operators spent a large portion of operating time in axial twisting postures. Peak compressive forces, shear loading and twisting moments were all below injury thresholds. It is apparent that while operating a LT, driving postures such as forward flexion, lateral bending and axial twisting during sitting alter loading on the spine depending on the operating task, LT model and whether operators are carrying or not carrying a load on the forks. LT operators adopt several awkward postures while performing everyday work tasks; however, it is still unknown whether these awkward and static postures play a major rote in the development of LBP. This study should be considered an initial step towards understanding postural stresses and spinal loading in LT operators. Cumulative compressive loading should be considered a more comprehensive and likely risk factor for injury in LT operators compared to peak compressive loading.