Functional Stability Limits during Reaching Tasks

Abstract

There is a need for stability constraints to be incorporated into ergonomic job analyses. The purpose of this study was to define functional stability limits for persons performing various reaching tasks. Forty-seven volunteers stood on a force plate and leaned as far as possible anterior, posterior and right and left diagonally. Functional stability limits were defined as the percent of the entire base of support through which subjects voluntarily displaced their center of pressure. Results showed that participants displaced their center of pressure from a minimum of 59.7% posterior with feet in a comfortable stance to 85.5% when stepping diagonally right or left toward the lean direction. The height and weight of an external load, and whether it was held in one or both hands, did not significantly affect the stability limits. These results can be used to introduce stability constraints into ergonomic job analyses.