Effect of prolonged sitting on body-seat contact pressures among quay crane operators: A pilot study.

BACKGROUND Quay crane operators are specialized in moving containers to and from vessels while adopting constrained sitting postures for prolonged periods (4-6 consecutive hours) in a very challenging environment. Thus, they are exposed to discomfort or pain that may result in deterioration of their performance with consequent reduction of operational safety levels. Such discomfort can be indirectly and partially assessed by measuring contact pressure at the body-seat interface. OBJECTIVES The aim of the study was to assess the feasibility, usefulness, and effectiveness of monitoring the variations in seat-body interface pressure during a regular work shift of 4 hours performed in a simulated environment. METHODS Eight professional operators performed a four-hour shift in a realistic control station set inside a quay crane simulator. Seat-body contact pressures were measured at 10 Hz using two pressure-sensitive mats placed on the seat pan and the backrest. Raw pressure data were processed to extract pressure vs. time curves related to the whole seat surface and, for the seat pan only, values associated with four anatomical regions (i.e. left and right thighs and buttocks). RESULTS During the work shift, the mean backrest pressure was low and fairly constant. Seat pan pressure increased by 10%, rising from 7.4 (1.5) to 8.2 (2.3) kPa over the simulated shift. Detailed analysis of the four sub-regions revealed that as the trial progressed the mean contact pressure on buttocks decreased (-6% at the end of the trial) while thigh pressures increased (by 10 and 20% for right and left sides, respectively). CONCLUSIONS Although further studies with larger samples are needed, long-term monitoring of the body-seat contact pressures of crane operators in a simulated environment appears to be a useful tool to identify specific postural strategies to reduce discomfort originated by prolonged sitting posture.