A, B, C, D, E, and A’, B’, C’, D’, E’	Guiding points related to $hGR{F}_{v,j}\left(t\right)$ (Figure 3a)
ap	Anterior-posterior direction
$CoP\left(t\right)$	Trajectory of center of plantar pressure
DS	Double-support phase of the walking gait
$Er{r}_i\left(t\right)$	Error in estimation of the total $hGR{F}_i\left(t\right)$ $i\in \left\{v,ap,ml\right\}$ (Equation (2))
F, G, H, I, J, K, L and F’, G’, H’, I’, J’, K’, L’	Guiding points related to $hGR{F}_{ap,j}\left(t\right)$ (Figure 3c)
Total $GR{F}_i\left(t\right)$	Total (right and left foot) walking force $i\in \left\{v,ap,ml\right\}$
Left $GR{F}_i\left(t\right)$	Left foot walking force $i\in \left\{v,ap,ml\right\}$
Right $GR{F}_i\left(t\right)$	Right foot walking force $i\in \left\{v,ap,ml\right\}$
$hGR{F}_{i,j}\left(t\right)$	Left and right foot $GR{F}_i\left(t\right)$ signals corresponding to half of a gait cycle $i\in \left\{v,ap,ml\right\}$ and $j\in \left\{l,r\right\}$
IMU	Inertial Measurement Unit
M, N, O, P, Q, R, S and M’, N’, O’, P’, Q’, R’, S’	Guiding points related to $hGR{F}_{ml,j}\left(t\right)$ (Figure 3e)
ml	Medial-lateral direction
n	Order of the polynomial curve
NRMSE	Peak-to-peak normalized root mean square error (Equation (1))
${\mu }_{NRMSE}$	Mean value of NRMSE values
${\sigma }_{NRMSE}$	Standard deviation of NRMSE values
$P_n\left(t\right)$	Polynomial of degree n
pdf	Probability Distribution Function
$S_j\left(t\right)$	Error scaling function $j\in \left\{l,r\right\}$ (Equations (5) and (6))
SS	Single-support phase of the walking gait
$T$	Length of the resampled $hGR{F}_{i,j}\left(t\right)$ signals ($T=100$)
$t_k$	Timing of guiding points (resampled to 100 points) $k\in \left\{A-E, A^{\prime }-E^{\prime }\right\}$
TPM	Twin Polynomial Method
v	Vertical direction
$y_k$	Normalized amplitude of guiding points $k\in \left\{A-E, A^{\prime }-E^{\prime }\right\}$