## 4 Discussion  
The aim of this study was to investigate the association between ankle injuries and lower limb ROM asymmetry in male university soccer players. The results are generally in line with our expectations. The study revealed significant differences in right passive knee flexion ROM, left and right active ankle plantarflexion ROM, and left active ankle dorsiflexion ROM when comparing the injury group and non-injury group. In the injury group, left passive knee flexion ROM and right active ankle plantarflexion ROM were significantly greater than those of the contralateral side. In the non-injury group, left passive knee extension ROM was significantly greater than that on the right side. Notably, the most significant result of this study is that athletes' right passive knee flexion ROM and right active ankle plantarflexion ROM were found to be significantly negatively correlated with the presence of ankle injuries. The findings of this study are significant for understanding the underlying mechanisms of ankle injuries. By identifying the relationship between ROM asymmetry and ankle injuries, it provides a new perspective for sports injury prevention. Meanwhile, these findings can assist coaches and sports medicine specialists in developing targeted training programs to improve athletes' joint ROM symmetry, thereby reducing the risk of ankle injuries.  
Previous research suggests that flexibility is a critical biomechanical factor in sports performance. Therefore, we assessed lower limb asymmetry by measuring the ROM.  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Crude**} & \multicolumn{3}{c}{**Model 1**} & \multicolumn{3}{c}{**Model 2**} \\ \cline{2-10}  & **OR** & **95\% CI** & _p_**-Value** & **OR** & **95\% CI** & _p_**-Value** & **OR** & **95\% CI** & _p_**-Value** \\ \hline Right PKFT & 0.91 & 0.84–0.99 & 0.027 & 0.86 & 0.77–0.97 & 0.011 & 0.88 & 0.77–0.99 & 0.037 \\ Right AAPFT & 0.89 & 0.81–0.99 & 0.024 & 0.86 & 0.76–0.98 & 0.020 & 0.84 & 0.73–0.98 & 0.026 \\ \hline \hline \end{tabular}  
* Notes: Crude was the unadjusted model; Model 1 adjusted for age (continuous variable), height (continuous variable), weight (continuous variable), and body mass index (continuous variable); Model 2 included the factors from Model 1 plus the number of training sessions per week (continuous variable), duration of each training session (continuous variable), and total weekly training hours (continuous variable). PKFT: passive knee flexion test; AAPFT: active ankle plantarflexion test.  
\end{table}
Table 4: Logistic regression analysis of the right PKFT and right AAPFT in relation to ankle injuries.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Injury Group** & **Non-Injury Group** & **\(p\)-Value** \\  & **(n = 21)** & **(n = 29)** & **\(p\)-Value** \\ \hline Left AAPFT (\({}^{\circ}\)) & 29.42 \(\pm\) 5.70 ** & 36.55 \(\pm\) 8.14 & 0.002 * \\ Right AAPFT (\({}^{\circ}\)) & 33.41 \(\pm\) 7.31 ** & 38.82 \(\pm\) 8.64 & 0.029 * \\ Left AADFT (\({}^{\circ}\)) & 15.83 \(\pm\) 6.37 & 20.61 \(\pm\) 8.35 & 0.033 * \\ Right AADFT (\({}^{\circ}\)) & 16.00 \(\pm\) 7.02 & 20.90 \(\pm\) 9.51 & 0.114 \\ \hline \hline \end{tabular}  
* Values are mean \(\pm\) SD. AAPFT: active ankle plantarflexion test; AADFT: active ankle dorsiflexion test. The _p_-values in the table refer to the data of the injury group and the non-injury group. *_p_ value \(<\) 0.05, between injury and non-injury sides. **_p_ value \(<\) 0.05, between the left AAPFT and right AAPFT in the injury group.  
\end{table}
Table 3: Description of the AAPFT and AADFT data for the injury and non-injury groups.  
Alterations in force within the ROM can increase the speed, frequency, and duration of joint loading. When the ROM limit is reached, muscles act to stabilize the joint as anticipated [29].