## 4 Discussions and Recommendations  
The objective of this study was to consolidate the existing knowledge and methods pertaining to FEA on human body-seat interactions for seat or bed design. Section 3 outlines the steps and various methods used during each stage of the simulation. A comparative understanding of the different methods utilized is of great importance and facilitates the opportunity to create guidelines for future research in the field. Additionally, it must be noted that the observed differences between methodologies are due to the different resources, research purposes, and desired accuracy levels. First, the acquisition of the required data for generating the geometry model varies significantly from one paper to another. The use of different data sources is based on the required accuracy of the models. If differentiation between muscles, fat, and skin is desired, medical imaging techniques should be used; otherwise, the use of anthropometric data is a simpler and cost-effective solution. The findings revealed that detailed models are mainly needed in the evaluation of pressure ulcers and other clinical applications. The studies concerned with automotive and seat manufacturing applications (focused on comfort) used models without a detailed representation of the soft tissues. While most papers used MRI data [18; 19; 23; 24; 25; 26; 50] as their main data source, other papers have used geometric databases [16; 17; 19; 21; 27; 28; 31; 32; 36; 37; 38; 39; 41; 43], such as POSER, 3 dcadbrowser, and Human builder, or software that contains human body geometries [1; 15; 29; 30; 33; 35; 44], such as ANYBODY, CASIMIR, and MADYMO, which use MRI scans as the main data source and provide accurate models for different kinds of simulation. The choice of the population percentile to be used for the study depends on the availability of subjects for the simulation and the purpose of the simulation. The use of models from full-body model software is the fastest and most validated method because it has been refined iteratively over years and improved through different versions. The THUMS [7] model created by Toyota has been made available to research institutions and can be used for the purpose of seat design. Figure 5 (left) shows the most commonly chosen methodology for acquiring data. After acquiring the model data, the next step is creating the model geometry. Figure 5 (middle) shows the percentage of papers that chose to conduct their research by modeling specific sections of the body or using the full-body geometry. The full-body geometry composition, as shown in Figure 3, is used when different sections of the human body are being studied: specifically, the interaction between the seat pan and the human buttocks section and the interaction between the human back and the seat back rest [1]. However, the level of detail of the model depends on the desired accuracy of the simulation. Modeling of specific parts of the body has many advantages, such as time efficiency when constructing models and more accurate results when specific problems are tackled. For example, if the focus in the design of a seat is to make the seat pan more comfortable, the use of a thigh and buttocks section model is appropriate. Alternatively, if the focus of the seat design is to create a seat that is optimized for comfort in general, then the use of a full-body model is a better choice as it provides meaningful results regarding the interaction of the seat pan and seat back rest with the buttocks and back. It is recommended that a simulation is performed that combines skin with soft tissue to obtain time efficiency, instead of having them separated. As shown in Figure 5 (right), combining the skin with the soft tissues is the most common method used. The non-combined choice is more practical when investigating pressure ulcers as it provides better insight into the creation of ulcers in a specific area.