## 4 Discussion
\begin{table}
\begin{tabular}{l l l l l l l l l} \hline \hline  & & \multicolumn{3}{c}{**Young Adults**} & \multicolumn{3}{c}{**Older Adults**} & \multicolumn{3}{c}{**Effect**} \\ \hline
**Phase** & **Parameters** & **Spontaneous** & **Fast** & **Spontaneous** & **Fast** & **Speed** & **Group** & **Speed \(\times\) Group** \\ \hline \multirow{2}{*}{P1} & AP & 1.48 \(\pm\) 0.48 & 3.10 \(\pm\) 1.02 & 2.18 \(\pm\) 0.78 & 3.62 \(\pm\) 1.34 & \(p\) \(<\) 0.001 & ns & ns \\ \cline{2-9}  & ML & 0.97 \(\pm\) 0.28 & 1.21 \(\pm\) 0.56 & 1.23 \(\pm\) 0.42 & 1.40 \(\pm\) 0.54 & \(p\) \(=\) 0.026 & ns & ns \\ \hline \multirow{2}{*}{P2} & AP & 3.14 \(\pm\) 0.59 & 6.02 \(\pm\) 1.79 & 4.19 \(\pm\) 0.95 & 7.02 \(\pm\) 2.26 & \(p\) \(<\) 0.001 & \(p\) \(=\) 0.036 & ns \\ \cline{2-9}  & ML & 1.13 \(\pm\) 0.31 & 2.69 \(\pm\) 0.68 & 1.42 \(\pm\) 0.32 & 2.36 \(\pm\) 0.71 & \(p\) \(<\) 0.001 & ns & \(p\) = 0.013 \\ \hline \multirow{2}{*}{P3} & AP & 3.08 \(\pm\) 0.73 & 5.00 \(\pm\) 1.70 & 4.30 \(\pm\) 0.81 & 6.95 \(\pm\) 2.58 & \(p\) \(<\) 0.001 & \(p\) = 0.004 & ns \\ \cline{2-9}  & ML & 1.64 \(\pm\) 0.47 & 3.47 \(\pm\) 1.44 & 2.11 \(\pm\) 0.40 & 3.06 \(\pm\) 1.01 & \(p\) \(<\) 0.001 & ns & \(p\) = 0.04 \\ \hline \multirow{2}{*}{P4} & AP & 3.54 \(\pm\) 0.56 & 6.23 \(\pm\) 1.21 & 4.46 \(\pm\) 0.93 & 7.49 \(\pm\) 1.83 & \(p\) \(<\) 0.001 & \(p\) = 0.007 & ns \\ \cline{2-9}  & ML & 1.07 \(\pm\) 0.43 & 2.13 \(\pm\) 0.87 & 1.53 \(\pm\) 0.32 & 2.33 \(\pm\) 0.72 & \(p\) \(<\) 0.001 & ns & ns \\ \hline \multirow{2}{*}{P5} & AP & 1.09 \(\pm\) 0.21 & 1.85 \(\pm\) 0.51 & 0.90 \(\pm\) 0.21 & 1.52 \(\pm\) 0.49 & \(p\) \(<\) 0.001 & \(p\) = 0.031 & ns \\ \cline{2-9}  & ML & 0.69 \(\pm\) 0.25 & 0.86 \(\pm\) 0.25 & 0.59 \(\pm\) 0.14 & 0.82 \(\pm\) 0.24 & \(p\) \(<\) 0.001 & ns & ns \\ \hline \multirow{2}{*}{Total} & AP & 4.27 \(\pm\) 0.64 & 7.35 \(\pm\) 1.64 & 5.56 \(\pm\) 0.95 & 9.10 \(\pm\) 2.53 & \(p\) \(<\) 0.001 & \(p\) = 0.005 & ns \\ \cline{2-9}  & ML & 2.21 \(\pm\) 0.63 & 4.06 \(\pm\) 1.27 & 2.67 \(\pm\) 0.34 & 3.82 \(\pm\) 0.87 & \(p\) \(<\) 0.001 & ns & ns \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Ranges of the dimensionless distances along the anteroposterior (AP) and mediolateral (ML) axis (\(\times\)100) for each phase and throughout the entire stepping. ‘ns’ indicates a non-significant effect (\(p>0.05\)). of the COM and the positive value corresponds to a backward angular acceleration, meaning that an insufficient global positive angular speed of the body at the beginning of the swing phase could lead to falling backwards. This result is in accordance with the previous work of [PERSON] et al. [38]. In a similar manner, the minimal distance along the mediolateral axis is observed at the end of the first swing phase (P2). Accordingly, this means that the MMA is located more laterally towards the non-dominant leg than the COM, while the dominant leg is swinging. It confirms global positive angular acceleration around the anteroposterior axis and the fall of the body toward the swing leg. This lateral fall stops at the beginning of the double-stance phase (P3). Conversely, the maximal mediolateral distance is observed during the swing phase of the non-dominant leg (P4). During this phase, the mediolateral distance is positive, meaning an ipsilateral fall of the body, i.e., toward the non-dominant leg. In the middle of the double-stance phase P3, the sign of the distance changes from negative to positive value. This result highlights the transition of the COM from the dominant to the non-dominant side. All these results are in accordance with previous data [39; 40]. Another interesting result is the evolution of the mediolateral distance during the APAs. During a large part of the phase P1, the distance along the mediolateral axis is positive and becomes negative at the time of heel lift of the dominant leg. This positive value highlights a displacement of the COM towards the non-dominant side before the swing of the dominant leg, which is in line with previous observations during the APAs [16; 17; 18].