Evaluation of spinal loads and chair design in seated work tasks.

In this research, several methods were employed simultaneously in the evaluation of chair design and seated work tasks. These methods were grouped under four headings, namely biomechanical load, posture, discomfort and body height shrinkage. The methods were used in both field and laboratory studies. The tasks investigated included forward force development, assembly work with restricted knee-room, vision to one side, grinding, punch press work and fork lift truck driving. Two or more chair designs were compared for each task. The results from the methods were in agreement with one another. It was shown that more flexed spinal postures caused increased biomechanical load on the spine, increased discomfort and increased body height shrinkage. The methods were found to have limitations in different situations.