## 4 Discussion  
An understanding of the influence of external perturbations on gait dynamics can assist clinicians and researchers in the design of personalised rehabilitation programmes aimed at improving balance, stability, and overall gait function. These programmes can reduce the risk of falls and enhance mobility and quality of life for individuals with neuromuscular impairments or age-related declines in gait performance. This study aimed to provide support for this field by identifying the most vulnerable phase of the gait cycle \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Parameter**} & **Initial Contact** & **Mid Stance** & **Pre-Swing** & **Treadmill Gait** & **IC vs. N** & **MS vs. N** & **PS vs. N** \\  & **(IC)** & **(MS)** & **(PS)** & **(N)** & **(N)** & **(N)** & **(N)** \\ \hline \hline \multicolumn{8}{c}{Kinematic parameters [deg]} \\ \hline Ankle max (df) & 21.38 \(\pm\) 3.96 & 17.66 \(\pm\) 4.75 & 19.3 \(\pm\) 3.54 & 15.65 \(\pm\) 2.18 & 36.61\% * & 12.84\% & 23.32\% * \\ Ankle min (pf) & \(-\)23.91 \(\pm\) 9.42 & \(-\)16.92 \(\pm\) 9.26 & \(-\)20.93 \(\pm\) 8.22 & \(-\)4.96 \(\pm\) 2.25 & 382.06\% * & 241.13\% * & 321.98\% * \\ Knee max (flex) & 79.21 \(\pm\) 8.34 & 68.08 \(\pm\) 6.62 & 77.71 \(\pm\) 6.69 & 70.56 \(\pm\) 3.19 & 12.26\% * & \(-\)3.51\% & 10.13\% * \\ Knee min (ext) & 3.66 \(\pm\) 2.91 & 2.57 \(\pm\) 3.85 & 3.4 \(\pm\) 3.81 & \(-\)3.28 \(\pm\) 1.95 & \(-\)211.59\% * & \(-\)178.35\% * & \(-\)203.66\% * \\ Hip max (flex) & 40.25 \(\pm\) 5.06 & 33.76 \(\pm\) 4.41 & 38.92 \(\pm\) 5.21 & 31.03 \(\pm\) 3.19 & 29.71\% & 8.8\% & 25.43\% * \\ Hip min (ext) & \(-\)9.33 \(\pm\) 4.15 & \(-\)11.34 \(\pm\) 4.22 & \(-\)14.43 \(\pm\) 3.57 & \(-\)14.72 \(\pm\) 2.64 & \(-\)36.62\% * & \(-\)22.96\% & \(-\)1.97\% \\ \hline \hline \multicolumn{8}{c}{Kinetic parameters [Nm/kg]} \\ \hline Ankle max (df) & 1.57 \(\pm\) 0.37 & 1.75 \(\pm\) 0.23 & 1.88 \(\pm\) 0.15 & 1.75 \(\pm\) 0.09 & \(-\)10.29\% & 0\% & 7.43\% \\ Ankle min (pf) & \(-\)0.08 \(\pm\) 0.09 & \(-\)0.24 \(\pm\) 0.04 & \(-\)0.11 \(\pm\) 0.05 & \(-\)0.11 \(\pm\) 0.04 & \(-\)27.72\% * & 118.18\% * & 0\% \\ Knee max (flex) & 1.15 \(\pm\) 0.29 & 0.64 \(\pm\) 0.26 & 0.36 \(\pm\) 0.05 & 0.33 \(\pm\) 0.04 & 248.48\% * & 93.94\% * & 9.09\% \\ Knee min (ext) & \(-\)0.66 \(\pm\) 0.21 & \(-\)0.38 \(\pm\) 0.08 & \(-\)0.51 \(\pm\) 0.08 & \(-\)0.31 \(\pm\) 0.03 & 112.9\% * & 22.58\% & 64.52\% * \\ Hip max (flex) & 1.09 \(\pm\) 0.23 & 0.55 \(\pm\) 0.1 & 0.7 \(\pm\) 0.16 & 0.61 \(\pm\) 0.11 & 78.69\% & \(-\)9.84\% & 14.75\% \\ Hip min (ext) & \(-\)0.54 \(\pm\) 0.15 & \(-\)0.78 \(\pm\) 0.16 & \(-\)1.09 \(\pm\) 0.23 & \(-\)0.63 \(\pm\) 0.05 & \(-\)14.29\% & 23.81\% * & 73.02\% * \\ \hline \hline \end{tabular}  
* IC—Initial Contact, MS—Mid Stance, PS—Pre-Swing gait phases, N—standard treadmill gait, df—dorsiflexion, pf—plantarflexion, flex—flexion, ext—extension, and *—significance level \(p<0.05\). Negative values alongside percentages indicate the extent of decrease compared to treadmill gait or whether the sign has been reversed.  
\end{table} 
Table 2: Mean, standard deviation, and percentages of extreme values for lower limb joint kinematics and kinetics curves calculated across all participants containing the impact of induced acceleration perturbation at the selected gait phases, compared to gait without perturbations. to perturbation and the highest overloads that occur during the perturbation. This study employed a perturbation protocol using the Grail system (Motek Medical BV, Amsterdam, The Netherlands), which allowed for the precise timing and intensity control of perturbations. The findings indicate that all perturbations significantly influenced the examined parameters, probably due to the application of high perturbation force [4]. A consistent significant alteration observed across all perturbations was the reduction in full knee extension, as evidenced by the knee joint angle curves (Figure 6B) and extreme values for the knee extension angle (Table 2).