Being seated for long periods, while part of many leisure or occupational activities, can lead to discomfort, pain and sometimes health issues. The impact of prolonged sitting on the body has been widely studied in the literature, with a large number of human-body finite element models developed to simulate sitting and assess seat-induced discomfort or to investigate the biomechanical factors involved. Here, we review the finite element models developed to investigate sitting discomfort or risk of pressure sores. Our study examines finite element models from twenty-seven papers, seventeen dedicated to assessing seating discomfort and ten dedicated to investigating pressure ulcers caused by prolonged sitting. The models' mesh composition and material properties are found to differ widely. These models share a lack of validation and generally make little allowance for anthropometric diversity.

The work is partly supported by Direction Générale de l'Aviation Civile (project n°2014 930818). ManuscriptA case study of the effects of foam and seat pan inclination on the deformation of seated buttocks measured using MRI Occupational ApplicationsWe investigated the effects of seat pan inclination and foam on the deformation of the seated buttocks using an upright MRI system. From observations among four healthy males, we found that soft tissue deformation under the ischial tuberosity (IT) could be reduced not only by using a soft cushion, but also by decreasing the shear force on the seat pan surface. These results suggest that soft tissue deformation could be used as an objective measure for assessing seating discomfort and injury risk, by accounting for the effects of both contact pressure and shear. We also confirmed that the gluteus maximus (GM) muscle displaced away from the IT once seated. As peak pressure and shear are most likely located below the IT, more realistic computational human body models in this region are needed that consider muscle sliding.

A personalized pelvis and femur shape is required to build a finite element buttock thigh model when experimentally investigating seating discomfort. The present study estimates the shape of pelvis and femur using a principal component analysis (PCA) based method with a limited number of palpable anatomical landmarks (ALs) as predictors. A leave-one-out experiment was designed using 38 pelvises and femurs from a same sample of adult specimens. As expected, prediction errors decrease with the number of ALs. Using the maximum number of easily palpable ALs (13 for pelvis and 4 for femur), average errors were 5.4 and 4.8 mm respectively for pelvis and femur. Better prediction was obtained when the shapes of pelvis and femur were predicted separately without merging the data of both bones. Results also show that the PCA based method is a good alternative to predict hip and lumbosacral joint centers with an average error of 5.0 and 9.2 mm respectively.

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