## 3 Results
### Finite Element Analysis Results  
Four different morphological models (tall-large, tall-thin, small-large, and small-thin) were treated with eight different lumbar belts. This means we have 32 results in total. The mechanical properties of the materials are assumed to be identical for all subjects in order to not consider these parameters as variable of analysis. Figure 5 shows a trunk FE model and its numerical results: (a) applied pressure by the belt and boundary conditions and (b) deformed shape of a trunk superposed on its initial shape. We could see the abdomen is pushed back by the belt wearing, where (c) the deformation of the spine is superimposed on its initial shape and the (d) pressure distribution is superimposed on the intervertebral discs. In order to show the mechanical effects on the spine, a Python script was used to automatically extract and analyse the results from Abaqus. This script isolates the different intervertebral discs and exports the pressures from their mid-surfaces. The script also isolates each vertebra and extracts the reaction forces and moments, as well as the coordinates  
Figure 4: Comparison of pressure applied by the different lumbar belts on the four different trunks. (**a**) Mean pressure (mmHg) of the belts. (**b**) Pressure at the last quintile (mmHg). (**c**) Pressure variation (%). It is characterized by the ratio of the first quintile to the last one. of the belt nodes. The results extracted from the simulation are loaded into Matlab, and a script automates the generation of a figure. An example is presented in Figure 5e. The following different variables related to the mechanical or therapeutic impact were chosen for analysis of the effects of the belt:  
* Variation of the angle of lordosis (\({}^{\circ}\)),
* Maximum and minimum pressure of all points on intervertebral discs (MPa),
* Mean pressure of all points on intervertebral discs (MPa),
* Maximum and minimum moments of all vertebrae of the model (N.m),
* Maximum and minimum forces on the vertebrae (N),
* Mean pressure applied by the belt to the trunk (MPa). Only the results used for the correlation of parameters (Table 4) are shown in Figure 6 (specific data in the Supplementary Materials). Figure 5: An FEM model and results of the trunk: (**a**) Applied pressure (MPa) and boundary conditions. (**b**) Deformed shape superimposed on its initial one (scale factor = 10) (mm). (**c**) An example of deformed shape of the spine (mm). (**d**) Pressure distribution on intervertebral discs (MPa). (**e**) An example of results on the spine obtained by Python script. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline  & Max & Min & Min & Difference & Mean & 5 th quintile & Pressure \\  & pressure—All & pressure—All & pressure—All & moment & of Lordosis & pressure & pressure & variation \\  & points (MPa) & points (MPa) & (N.mm) & angle (\({}^{\circ}\)) & (mmHg) & (mmHg) & (mmHg) \\ \hline Max pressure—All & 1.00 & -0.94 & -0.96 & -0.79 & 0.77 & 0.61 & 0.44 \\  & points (MPa) & -0.94 & 1.00 & 0.93 & 0.93 & -0.88 & -0.64 & -0.44 \\ \hline Min moment (N.mm) & -0.96 & 0.93 & 1.00 & 0.76 & -0.84 & -0.68 & -0.45 \\ \hline Difference of & -0.79 & 0.93 & 0.76 & 1.00 & -0.77 & -0.52 & -0.41 \\ Lordosis angle (\({}^{\circ}\)) & -0.77 & -0.88 & -0.84 & -0.77 & 1.00 & 0.77 & 0.46 \\ \hline Mean pressure (mmHg) & 0.61 & -0.64 & -0.68 & -0.52 & 0.77 & 1.00 & 0.86 \\ \hline Pressure variation (mmHg) & 0.44 & -0.44 & -0.45 & -0.41 & 0.46 & 0.86 & 1.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Correlation between the biomechanical and therapeutic parameters of the four typical patients (Pearson method): Blue box means a strong relationship and orange a weak one. Figure 6: Different variables related to the mechanical or therapeutic impact. (**a**) Correction of lordosis angle (\({}^{\circ}\)); (**b**) maximum and minimum pressures of all points on intervertebral discs (MPa). Full and hatched bars show maximum and minimum values, respectively; (**c**) maximum and minimum moments of all vertebrae (N.mm).