## 4 Discussion  
The identification of potential risk factors for LBP is crucial in terms of disease prevention and treatment. This study analyzed the properties of resting lumbar muscles using a handheld myotonometer for LLAs with a high risk of LBP to understand LBP in patients with lower limb amputation. The most notable point in the results of this study is the significant increase in the stiffness and frequency of the upper lumbar region on the NAS of amputees. The stiffness of the NAS (329.1 N/m) increased by 8.5% and 16.9%, respectively, compared with those of the AS (303.2 N/m) and CG (281.6 N/m), and the frequency of the NAS (17.4 Hz) was increased by 5.5% and 12.3%, respectively, compared with that of the AS (16.5 Hz) and CG (15.5 Hz). In particular, in the amputees, the difference between the AS and NAS of the upper lumbar was significantly increased more than that in the lower lumbar. However, there was no significant difference between the right and left sides of the upper lumbar in the CG. Therefore, unlike the CG, bilateral differences in stiffness and frequency can be interpreted as a potential risk factor related to LBP in the amputees. In our study, there was no difference in the stiffness of the right and left portions in the CG. However, in a similar previous study using the portable MyotonPro, comparing the stiffness of the right and left sides of 20 young male and female adults, it was reported that males and the right side had greater stiffness than females and the left side, respectively. This was affected by the right-hand dominance (all subjects in the study had right-handed dominance) and low-level CNS activation, suggesting further study of the effect of gender difference [18]. In a study by [PERSON] et al., the stiffness was measured a total of three times with an interval of one week, and the difference in mean values measured over 3 weeks was compared. The men who participated in the experiment showed stiffness values in the range of 231.7 N/m to 267.7 N/m, and there was little difference between the left and right mean values at week 1 (234.6 N/m vs. 236.3 N/m). However, it can be seen that the difference between the left and right increased significantly in the second (242.9 N/m vs. 257.5 N/m) and third weeks (231.7 N/m vs. 264.3 N/m). In the discussion, the authors said that the inter-individual variance increased more than the intra-individual variance \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multirow{2}{*}{**Lumber Part**} & \multicolumn{2}{c}{**Lower Limb Amputees**} & \multirow{2}{*}{**CG (C)**} & \multirow{2}{*}{**F Value**} & \multirow{2}{*}{**Tukey HSD**} \\ \cline{3-3} \cline{5-7}  & & **AS (A)** & & & & \\ \hline \multirow{2}{*}{\begin{tabular}{c} **Stiffness** \\ **(N/m)** \\ \end{tabular} } & Upper & 303.2 \(\pm\) 51.3 \({}^{\lx@sectionsign}\) & 329.1 \(\pm\) 51.2 & 281.9 \(\pm\) 38.0 & 3.291 \({}^{*}\) & B\textgreater{}C \\ \cline{2-7}  & Lower & 225.9 \(\pm\) 51.2 & 237.6 \(\pm\) 61.3 & 226.4 \(\pm\) 43.6 & 0.192 & NS \\ \hline \multirow{2}{*}{\
\begin{tabular}{c} **Frequency** \\ **(Hz)** \\ \end{tabular} } & Upper & 16.5 \(\pm\) 1.9 & 17.4 \(\pm\) 1.5 & 15.5 \(\pm\) 1.2 & 4.455 \({}^{*}\) & B\textgreater{}C \\ \cline{2-7}  & Lower & 14.0 \(\pm\) 1.4 & 14.1 \(\pm\) 1.5 & 14.2 \(\pm\) 1.6 & 0.082 & NS \\ \hline \multirow{2}{*}{
\begin{tabular}{c} **Decrement** \\ **(Ratio)** \\ \end{tabular} } & Upper & 1.25 \(\pm\) 0.24 & 1.17 \(\pm\) 0.17 & 1.21 \(\pm\) 0.29 & 0.336 & NS \\ \cline{2-7}  & Lower & 1.15 \(\pm\) 0.23 & 1.13 \(\pm\) 0.23 & 1.01 \(\pm\) 0.18 & 1.184 & NS \\ \hline \hline \end{tabular}  
* AS, amputated side; NAS, non-amputated side; CG, control group; \({}^{\lx@sectionsign}\) mean \(\pm\) standard deviation; \({}^{*}\)\(p<0.05\); NS, no significance.  
\end{table} 
Table 4: Comparison of lumbar muscle properties in AS, NAS, and CG. during the 3 weeks of measurement. They did not specify the reason for this, and they suggested further research.