## 3 Results  
### Body-Slip  
In this study, the differences in backrest sliding (BS), seat-sliding (SS) and total body-slip (TBS) between the double-sliding and non-sliding wheelchairs were analyzed when the wheelchairs were reclined and repositioned in the range of 100-130\({}^{\circ}\). In addition, the difference between the marker position in the initial upright position (IUP) before reclining and that in the return upright position (RUP) after repositioning was compared.  
Table 2 shows the results of the comparison of the amount of change in body-slip between double-sliding and non-sliding.  
During reclining, BS showed a tendency to decrease in both conditions, and the decrease in BS was 21.42 mm in non-sliding, which was significantly greater than that in double-sliding (\(p<0.05\)). The SS also showed a tendency to decrease in both conditions, and the decrease of SS in double-sliding was significantly decreased by 7.86 mm compared to that in non-sliding (\(p<0.05\)). The change in the TBS was 16.35 mm greater in non-sliding than in double-sliding (\(p<0.05\)).  
During repositioning, BS showed a tendency to increase in both conditions, and the increase of BS in non-sliding was significantly greater than that in double-sliding by 17 mm.  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Condition**} & \multirow{2}{*}{**Variable**} & \multicolumn{2}{c}{**Double-Sliding**} & \multicolumn{2}{c}{**Mean**} & \multirow{2}{*}{**SE**} & \multicolumn{2}{c}{**95\% CI**} & \multirow{2}{*}{**t-Value**} \\ \cline{3-4} \cline{6-9}  & & & & **Difference** & & & **Lower** & **Upper** \\ \hline \multirow{4}{*}{Reclining} & BS (mm) & \(-3.9\pm 7.6\) & \(-25.3\pm 24.3\) & 21.42 & 6.95 & 5.69 & 37.15 & 3.081 * \\ \cline{2-9}  & SS (mm) & \(-18.8\pm 10.3\) & \(-10.9\pm 5.6\) & \(-7.86\) & 2.49 & \(-13.49\) & \(-2.24\) & \(-3.164\) * \\ \cline{2-9}  & TBS (mm) & \(25.9\pm 7.6\) & \(42.2\pm 14.8\) & \(-16.35\) & 5.17 & \(-28.05\) & \(-4.64\) & \(-3.159\) * \\ \hline \multirow{4}{*}{Repositioning} & BS (mm) & \(1.5\pm 11.6\) & \(18.5\pm 23.2\) & \(-17.00\) & 5.39 & \(-29.20\) & \(-4.80\) & \(-3.153\) * \\ \cline{2-9}  & SS (mm) & \(20.2\pm 8.5\) & \(14.9\pm 6.4\) & 5.28 & 2.45 & \(-0.26\) & \(10.83\) & \(2.155\) \\ \cline{2-9}  & TBS (mm) & \(30.0\pm 7.6\) & \(40.8\pm 13.0\) & \(-10.82\) & 3.93 & \(-19.71\) & \(-1.92\) & \(-2.751\) * \\ \hline \multirow{4}{*}{IUP-RUP} & BS (mm) & \(-2.4\pm 7.7\) & \(-6.8\pm 9.4\) & 4.42 & 3.49 & \(-3.47\) & \(12.31\) & \(1.268\) \\ \cline{2-9}  & SS (mm) & \(1.5\pm 3.7\) & \(4.0\pm 4.6\) & \(-2.58\) & 2.33 & \(-7.84\) & \(2.68\) & \(-1.109\) \\ \cline{2-9}  & TBS (mm) & \(8.9\pm 6.8\) & \(12.9\pm 8.4\) & \(-4.00\) & 2.81 & \(-10.35\) & \(2.35\) & \(-1.425\) \\ \hline \hline \end{tabular}  
* IUP-RUP, initial upright position-return upright position; BS, back sliding; SS, seat sliding; TBS, total body sliding; SE, standard error; CI, confidence interval; *\(p<0.05\).  
\end{table}
Table 2: Comparison of slip variation between the two conditions (double-sliding versus non-sliding).  
In addition, SS showed a tendency to increase in both conditions, and although the increase of SS in double-sliding was greater than that in non-sliding, there was no statistically significant difference.  
The amount of change in TBS was 10.82 mm, which was significantly larger in non-sliding than in double-sliding (_p_ < 0.05). Regarding the difference in the amount of change in body-slip between RUP and IUP, BS decreased in both conditions, while SS showed a tendency to increase in both conditions. However, there were no statistically significant differences between the two conditions. Additionally, the amount of change in TBS was greater in non-sliding than in double-sliding; however, there was no statistically significant difference.