To better understand seating biomechanics, the normal and shear forces, chair positions, and seated postures of twenty-three mid-sized male subjects were measured and analyzed. These data were examined in relation to one another and the affects of chair position on both body posture and support forces were determined. Force data were collected and analyzed for both static and dynamic conditions using six multi-axis force plates mounted to an experimental chair under the thighs, under the buttocks, behind the pelvis, behind the thorax, and to a steering wheel and foot support. Postural data and chair movement data were collected using a motion measurement system.

These data were analyzed to determine what degree of motion was necessary in the experimental chair, in terms of recline and back support articulation, to produce statistically significant postural and loading changes for the mid-sized men. Significant differences were found across the subject sample in both the static and dynamic test trials.

The support force data in conjunction with subject anthropometry were also used to estimate the internal loading in the lumbar spine and evaluate that loading for one subject as his posture was varied.

Currently, the data presented for this dissertation are the only data of their kind. It is expected that the availability of these data will have a significant impact on seating design, seating evaluation and the tools used for design and evaluation.