# Assistance of a Person with Muscular Weakness Using a Joint-Torque-Assisting Exoskeletal Robot
## 5 Verification of Rehabilitation Effectiveness with a Case Study
### Assistance with Increasing Knee Extension Assistance  
During the case study, the patient experienced difficulty in weight bearing due to muscle weakness. The extension torque assist of the stance phase and the flexion torque assist of the swing phase were effective in the short- and long-term gait trainings. In order to observe the change in gait patterns according to the magnitude of the extension torque of one side (the weaker side), in particular, the 20 m path walking tests were performed using different torque profiles on the same training day.  
The walking data for three different conditions were collected. As shown in Figure 18, the extension torque of the stance phase of the right knee was different in each condition. In each case, the extension torque level of the right knee was set to 16.5, 18.5, and 20.4% of normal walking.  
Figure 19 shows the kinematic results of the three trials shown in Figure 18. No significant difference in the left and right stance phase periods was observed; however, with an increase of the right knee extension assistive torque, the hip extension range increased.  
The results of the analysis of gait parameters are shown in Table 6. In trial 3 and trial 1, the maximum hip extension angles of the left and right were 11.8 and 15.83 degrees greater, respectively. The first double support phase on the right can be considered to indicate the weight support preparation for the left swing. With an increase of the extension torque, the difference between the right and left of the double support phase reduced.  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Left** & **Right** \\ \hline Gait period (s) & 2.04 & 1.94 \\ Stance period (s) & 1.56 & 1.50 \\ Stance period (\%GC) & 76.47 & 77.32 \\ Opposite foot contact (\%GC) & 50.49 & 46.91 \\ Opposite foot off (\%GC) & 28.92 & 28.87 \\ Range of hip motion (degree) & 40.68 (\(-\)5.08 35.59) & 36.68 (\(-\)1.36 35.32) \\ Range of knee motion (degree) & 35.91 (21.34 57.24) & 45.77 (20.42 66.19) \\ \hline \hline \end{tabular}
\end{table}
Table 4: Gait parameters of bilateral crutches gait with Angel Legs.  
\begin{table}
\begin{tabular}{c c c} \hline \hline  & **Without Assistance** & **Robot Assistance** \\ \hline Oxygen cost (mL/kg/m) & 1.93 & 1.37 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Oxygen costs of the 6-min metabolic test of walking without assistance and walking with Angel Legs using bilateral crutches.  
Figure 18: Applied torque profiles of three trials for **(a)** left hip joint, **(b)** right hip joint, **(c)** left knee joint, and **(d)** right knee joint. Only the extension torques of the right knee joint were different in each case.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Without**} & \multicolumn{2}{c}{**Robot**} & \multicolumn{2}{c}{**Robot**} & \multicolumn{2}{c}{**Robot**} \\  & \multicolumn{2}{c}{**Robot**} & \multicolumn{2}{c}{**Assistance**} & \multicolumn{2}{c}{**Assistance**} & \multicolumn{2}{c}{**Assistance**} \\  & **Assistance** & **Trial 1** & **Trial 2** & **Trial 3** \\ \hline \multirow{2}{*}{Gait cycle (s)} & L & 2.75 & 2.28 & 2.10 & 1.93 \\  & R & 2.74 & 2.27 & 2.11 & 1.93 \\ \hline \multirow{2}{*}{First double support (\%Gait)} & L & 22.55 & 12.49 & 12.64 & 16.88 \\  & R & 29.56 & 24.13 & 23.46 & 18.58 \\ \hline \multirow{2}{*}{Single support (\%Gait)} & L & 26.55 & 34.18 & 34.45 & 34.30 \\  & R & 21.17 & 29.31 & 29.24 & 30.16 \\ \hline \multirow{2}{*}{Second double support (\%Gait)} & L & 34.91 & 24.13 & 23.49 & 18.96 \\  & R & 22.63 & 12.41 & 12.91 & 16.93 \\ \hline \multirow{2}{*}{Stance phase (\%Gait)} & L & 84.00 & 70.80 & 70.58 & 70.15 \\  & R & 73.36 & 65.87 & 65.61 & 65.68 \\ \hline \multirow{2}{*}{Maximum hip extension (deg)} & L & 26.32 & -5.32 & -14.32 & -17.12 \\  & R & 41.58 & -2.08 & -12.06 & -17.91 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Gait analysis results of trials.