Static force exertion in postures with different degrees of freedom.

In assessing human force exertion, the use of standardized postures can lead to the inaccurate prediction of the forces and postures which occur in everyday life. Therefore force data obtained using postures freely chosen by subjects themselves may be considered more relevant. A standardized posture, however, is 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, functional, and standardized postures. The difference in average force, though, is considerable and significant. The conclusion is that force exertion in free posture is most suitable for design research.