Assessing shoulder posture ergonomy thanks to a finite element analysis

The ability to predict discomfort is a major issue for scientists who are developing numerical dummies for the assessment of ergonomy. The bulk of the existing digital human models for ergonomic assessment consists in multi-body models able to simulate motion, for instance Jack, Safework and Ramsis (Delleman et al. 2004)). These models, as well as the currently used ergonomics method (RULA, REBA, LUBA, OWAS (Karhu et al. 1977; McAtamney and Corlett 1993; Hignett and McAtamney 2000; Kee and Karwowski 2001)), assess ergonomy by means of posture parameters, i.e. proximity of the joint end stops, implied loads, time and repetition, and more recently by means of dynamic parameters such as muscle forces (Rasmussen and De Zee 2012). However, they do not take into account the solicitations of biological tissues which are yet largely at the origin of the discomfort feeling. In this context, finite element (FE) models would offer the possibility of a finer modelling of the anatomy as well as the possibility of studying the stress and strain of the biological tissues. Furthermore, a future prospect of FE analysis could be a better understanding of the risks of musculoskeletal (MS) disorders, since these risks are associated with biological tissue inflammation. This study presents simulations of three different shoulder positions performed thanks to the use of a shoulder MS model and a shoulder FE model. The long-term achievement of this work will be to determine new biomechanical criteria concerning shoulder discomfort associated with a posture.