The pressure distribution and the location of the points of maximum pressure, usually below the ischial tuberosities, was measured for subjects sitting on a flat, hard and horizontal support, and varying angle of the rotation of the pelvis. The pressure data were analyzed for force-and pressure-related quantities. Multiple regression was applied to explore relationships between these quantities and (i) a set of body characteristics, and (ii) the pelvis rotation. The maximum pressure and the pressure gradient were mainly explained by the ectomorphic index, and the distance between the maximum pressure points by gender and the angle of rotation of the pelvis.

This paper surveys the current state of art of digital human body modeling with a focus on information inclusion and analyzes the results from the aspects of design and engineering. It presents the results of a literature study, which intended to investigate the modeling approaches within the mentioned categories, and to investigate the fidelity of models based on the information content. In view of the fact that modeling is always a simplified representation of reality, models with different information contents are developed for different applications. It is also discussed in this paper that the information content of human body models however reflects not only the aspect of application, but also the level of fidelity, or functional sophistication. Taking into consideration the sorts of information needed to model human body as a complex organic system, the authors propose an information content-based categorization. The major categories of aspect models of human body that have been incorporated in a stratified reasoning scheme are: morphological, material, structural, mechanical, physiological and behavioral models. One conclusion is that remarkable progress has been achieved in terms of sophistication of models (i.e., of information inclusion and processing methods). Another conclusion is that further increase of the fidelity of models will not be possible without the proper treatment of the concomitant complexities. Integration of various aspect models and real time computational processing of human models are inevitable in several fields of application. However, development of human body models of such a high sophistication goes together with an exponential growth in the required capacities. This leads us to a trade-off problem in digital human body modeling.

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With the increasing information-intensiveness of products, users are challenged with expanding options and possible ways to interact. Rapidly escalating numbers of possible useroperation sequences hinder designers in anticipating all possible (unacceptable) outcomes. Interactively simulating product models with human subjects to explore all options is not practicable. Virtual simulation with computer models of users can open the way towards faster-than-real-time performance and investigation of massive numbers of interaction sequences. This paper reports on opportunities to improve realism of virtual-use simulations by incorporating knowledge about the workings of the human brain We elaborate how, in particular, cognitive-architecture simulations developed by cognitive scientists and error phenotypes identified in human reliability analysis (HRA) can extend a virtual-use simulation approach that we have proposed in foregoing work, by offering the prospective of generating interaction sequences with erroneous user actions unforeseen by the designer. We outline how such an integrated system can be implemented and also discuss validation issues.

An optimization procedure was developed to search for the ergonomically optimum shape of consumer products. The entity to be optimized is a Finite Elements Model of the human body. The modification variable is the pressure values in the contact area. The Finite Elements Model and the optimization procedures were developed for a sitting support without backrest or arm rests. The model consists of a simplified assembly of the upper leg and the buttock area. Three components are included: skin, bony parts and in between a matrix of soft tissue. This paper presents the construction of the Finite Elements Model, in particular the assessment of the material properties according to the James-Green-Simpson elasticity model, and the first results of the Finite Elements Analysis. The first experiments are to validate the model for material properties. To that end the coefficients of the elasticity model are needed that cause good agreement of the maximum pressure values in the contact area with the predicted values obtained by earlier published regression. A hypothetical dependency of the maximum interface pressure on the stiffness is introduced. The results confirmed a part of the hypothesis. The current model needs further elaboration to test the hypothesis completely and to obtain a valid assessment of the material properties.