## 3 Results  
The initial CoM height and descent velocity are shown in Table 3. Since the harness support starts at a specified height, the variation in the initial CoM height is small. The variation in the contact parts is shown in Table 4. In most trials, the hands made contact with the ground first, but in some trials, the knees made contact with the ground before the hands. There were 12 trials where the contact part changed when joint torque conditions were altered. Among the 12 trials, there were 8 cases where the left and right hands changed, and 2 cases each where the contact part changed from hand to knee or knee to hand. Typical falling movements and joint patterns are shown in Figures 2 and 3. In the experiment, although the subject could not entirely prevent the fall, the harness support allowed for the fall to occur gradually. This means that while the body imbalance could not be corrected, the speed of impact was sufficiently reduced. This motion was identified as the reference motion for successfully mitigating the impact of the fall in this study. However, this motion could not be completely replicated, as the harness support's effects could not be mimicked by altering the torques in the lower limbs. Compared to recorded motions, the simulation model falls faster because of the lack of harness support. Furthermore, in the experiment, the descent speed of the trunk decreased before ground contact, and the ground was reached with both hands and feet almost at the same time. The joint torque of the elderly and young conditions increased to follow the original motion, which was the reference motion of this simulation, under the limitation of torque and torque change rate. The collision time, which is the time duration of the fall simulation, is shown in Figure 4. Although the time to collision is short due to the simulation beginning at the terminal phase of the fall, the delay in collision due to the generated torque of the lower limbs is apparent. There is a significant difference in collision time between different physical conditions. The collision time for the elderly was shortened by an average of 0.013 s compared to free fall (\(p=3.10\times 10^{-3}\)), while the collision time for young adults was shortened by an average of 0.027 s compared to free fall (\(p=5.28\times 10^{-6}\)). The contact velocity, which is the descent velocity of the contact point at the time of collision, is shown in Figure 5. There is a significant difference in contact velocity between different physical conditions. In the elderly condition, the contact velocity decreased by an average of 0.73 m/s compared to free fall (\(p=6.26\times 10^{-10}\)), while in the young adult condition, the contact velocity decreased by an average of 1.21 m/s compared to free fall (\(p=1.31\times 10^{-12}\)). Figure 3: Typical knee joint angle, angle velocity, and joint torque patterns of simulated fall movements. Figure 2: Typical fall movements. The CoM height and descent velocity at the time of collision are shown in Figures 6 and 7, respectively. There is a significant difference in both CoM height and descent velocity at the time of collision between different physical conditions. In the elderly condition, the CoM height at the time of collision was 0.03 m higher on average compared to free fall \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **Long-Step Case** & **Short-Step Case** & **\(p\)-Value** \\ \hline Initial height [m] & 0.75 \(\pm\) 0.039 & 0.76 \(\pm\) 0.034 & 0.296 \\ Initial descent velocity [m/s] & \(-1.0\)\(\pm\) 0.23 & \(-1.1\)\(\pm\) 0.33 & 0.196 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: CoM height and CoM descent velocity at initial condition. Figure 4: Time duration of fall simulation (\(\blacklozenge\) means the outlier. *: \(p\)\(<\) 0.017, **: \(p\)\(<\) 0.0033. They are at 5% and 1% significance levels). Figure 5: Descent velocity of contact point at the moment of ground contact (**: \(p\)\(<\) 0.0033. They are at 5% and 1% significance levels).