Effects of changes in work methods on musculoskeletal load. An intervention study in the trailer assembly.

The purpose of this case study was to identify the work cycles imposing high loads on the upper limb and low-back among trailer assembly workers for an ergonomic intervention. Several changes in work methods, tools and work organisation were implemented. The number of repetitions of fundamental work cycles and wrist posture were recorded from the video. Exposure imposed on the upper extremity in driving screws and drilling was computed based on experiments on force and time requirements. In lifting or carrying, the dose imposed on the low-back was computed based on the load moment on the L5/S1 disk and duration of the cycle. It was shown that after the intervention most workers worked less with deviated wrist and the cumulative exposure on the upper extremity was lower in furniture fixing tasks. Lifting with twisted torso was reduced. It was concluded that with relatively simple and low-cost solutions exposure to important risk factors of upper extremity and low-back disorders could be reduced.