Static Force Exertion in Standardized,Functional and Free Postures

In assessing human force exertion, the use of standardized postures can lead to inaccurate prediction of the forces and postures which occur in everyday life. Force data obtained using postures freely chosen by the subjects themselves may therefore be considered more relevant. A carefully standardized posture, however, is generally considered to yield more reliable data. The question arose whether it would be possible to combine the two in some way, calling the result a “functional posture”. Research was necessary to determine a way of operationalizing these functional postures, and to test their reproducibility.

First, a method is proposed to describe functional postures through explorative research. This includes the fixation of members that transfer force to the outside world, while the rest of the body is allowed to move freely. The results of further research show that the exerted force is reproducible in free, in functional, and in standardized posture. The difference in average force, though, is considerable and significant. The conclusion is that force exertion in free posture is most appropriate for design research.