## 2 Materials and Methods
### Personalization Algorithm  
The personalization provided the local geometrical and biomechanical details of the human body. Firstly, the scaling [7] was performed for each subject to target the given gender, age, height, and weight. Having the scaled model, the personalization to provide the correct anthropometric dimensions was carried out. The two-step approach is described as:  
\[T = S+P\] \[T(\mathbf{X}) = S(\mathbf{X})+\Delta S(\mathbf{X}) \tag{1}\] \[\mathbf{X}_{T} = \mathbf{X}_{S}+\Delta\mathbf{X}_{S}\]  
meaning \(T\) (target) equals \(S\) (scaling) plus \(P\) (personalization) where \(\mathbf{X}_{T}\) describes the coordinates of any point of the subject-specific (target) model referring to the same point \(\mathbf{X}\) in the reference model, which is firstly scaled to a semistate \(\mathbf{X}_{S}\) in the scaled model. \(\mathbf{X}\) refers to a spatial point in the global coordinate system with the origin in the H-point (the point in the middle between the hip joints) with the axis \(x\) (defining the depth) pointing anteriorly to the front. The sagittal plane is the plane \(xz\) (the axis \(z\) defining the height points cranially to the head), and the axis \(y\) (defining the width) is directed laterally from the right to the left forming the right-hand side system. Personalization was the next step after scaling. Scaling is a necessary step to have a model with global dimensions for the particular human body size before applying the mathematical operation to refine the surface locally. As the scaling algorithm was published previously, this paper does not address it, referring to the work by [PERSON] et al. [7]. For personalization purposes, the scaled model was divided into segments summarized in Table 3 and schematically shown in Figure 3. Each segment can be described by the anthropometric dimensions from Table 2 displayed in Figure 1. The personalization algorithm ran independently of each of the 16 subject-specific segments defined in Table 3 using the corresponding dimensions from Table 2. There was a reference node \(\mathbf{X}_{S0}^{\mathrm{s}}\) chosen on each segment as a local coordinate system origin, against which it was personalized, which also served to connect the neighboring segments following the open-tree segment system in the multibody structure. This is usually the joint connecting the neighboring segments [15]. The personalization benefited from the open-tree structure hierarchy, so the base body (to be personalized first) was the abdomen followed by the thorax, neck, and head upwards and the left and right thighs, the left and right calves, and the left and right feet downwards. The thorax was followed by the left and right arms, left and right forearms, and left and right palms. The reference model stood upright so that the local coordinate systems of all segments were aligned to the global coordinate system. The geometry and shape of a particular segment were given by the reference model; see Figure 2.  
Any node \(\mathbf{X}_{Si}^{s}\), \(i\in\{1,\dots,m\}\) (\(m\) being the numbers of nodes on the segment \(s\)) on the scaled model \(S\) is personalized as:  
\[\mathbf{X}_{Ti}^{s}=\mathbf{R}^{s}(\mathbf{X}_{Si}^{s}-\mathbf{X}_{S0}^{s})+ \mathbf{X}_{S0}^{s} \tag{2}\]  
where \(\mathbf{X}_{Ti}^{s}\) is the personalized node on target model \(T\) and \(\mathbf{R}^{s}=\mathbf{R}^{s}(\mathbf{X})\) is the transformation matrix for particular segment \(s\) depending on the spatial node position \(\mathbf{X}\). Although the personalization in Equation (2) holds for all segments, the transformation matrix \(\mathbf{R}^{s}\) contains the local scaling (personalization) coefficients to personalize a particular segment \(s\in\{0,\dots,15\}\) numbered according to Table 3. For each segment \(s\in\{0,\dots,15\}\), \(\mathbf{R}^{s}\) is a diagonal matrix with the space-dependent personalization coefficients in the global coordinate system, so that:  
\[\mathbf{R}^{s}= \begin{bmatrix}p_{x}^{s}(\mathbf{X})&0&0\\ 0&p_{y}^{s}(\mathbf{X})&0\\ 0&0&p_{z}^{s}(\mathbf{X})\end{bmatrix}