## 4 Discussion  
This study aimed to compare the effects of a 4-week balance training program, performed in isolation or combined with tDCS, on functional dynamic balance in recreationally active young adults. Two main findings can be highlighted: first, the balance exercise program established in this study was effective in improving dynamic balance; and second, combining it with 10 min of tDCS did not yield additional benefits compared to performing the program alone. These findings have important implications for designing effective and efficient ankle training and injury prevention programs. The significant improvements in the YBT and ET outcomes observed in both groups underscore the effectiveness of the balance training program in enhancing dynamic balance. Notably, in addition to the differences in the posteromedial and posterolateral directions of the YBT, the improvement observed in the CS is noteworthy. Both the BB and BB + tDCS groups achieved CS improvements of over 7% and 5%, respectively, exceeding the minimum detectable change recently established by [PERSON] et al. for this YBT component [41], thus indicating a genuine and meaningful change attributable to the intervention. According to the literature, a CS below 89.6% is associated with a higher risk of lower extremity injury in American football players [42]. While [PERSON] et al. highlight the importance of considering this threshold within population-specific contexts [31], our findings are particularly interesting, as participants demonstrated significant improvements, progressing closer to this critical threshold. Additionally, the absence of changes in the anterior component of the YBT following the intervention aligns with the findings of a previous study comparing the effects of a balance training program on dynamic balance using the BB and BOSU devices [9]. This may be attributed to the specific instability characteristics of the BB device, which predominantly induces movement in the frontal plane while offering limited demands in the sagittal plane. Moreover, we observed that the anterior component of the YBT largely depends on the dorsiflexion movement, which appears to be insufficiently addressed by the balance training interventions used in both the aforementioned study and the present one. In summary, the observed improvements in the YBT outcomes in the posteromedial and posterolateral directions can be attributed to the specific demands of the BB device, which challenges the participants' ability to stabilize in the frontal plane. Furthermore, the improvements in the performance of the ET (4.30 s and 5.03 s for the BB and BB + tDCS groups, respectively) are noteworthy. Although the ET is not widely used for balance assessment in adults, its reliability in adolescent populations [35], combined  
\begin{table}
\begin{tabular}{c c c c c c c} \hline  & \multicolumn{3}{c}{**Blackboard Group**} & \multicolumn{3}{c}{**Blackboard + tDCS Group**} & \multicolumn{1}{c}{ \begin{tabular}{c} **Group** \\ **Differences** \\ \end{tabular}  } \\ \cline{2-7}  & **Baseline** & **POST\_2W** & **POST\_4W** & **Baseline** & **POST\_2W** & **POST\_4W** & \(\boldsymbol{p(n^{2})}\) \\ \hline YBT—A & 0.63 (0.05) & 0.65 (0.05) & 0.64 (0.05) & 0.65 (0.07) & 0.66 (0.06) & 0.67 (0.05) & 0.507 (0.04) \\ \hline YBT—PM & 0.85 (0.19) & 0.96 (0.21) & 0.98 (0.17) & 0.80 (0.10) & 0.84 (0.14) & 0.89 (0.11) & 0.101 (0.14) \\ \(\mathtt{s(n^{2}=0.57)}\) & 0.94 (0.16) & 0.99 (0.14) & 1.01 (0.14) & 0.89 (0.10) & 0.90 (0.12) & 0.94 (0.11) & 0.375 (0.06) \\ \(\mathtt{s(n^{2}=0.40)}\) & 0.37 (0.06)  
with the relatively young average age of our participants, justified its inclusion in this study. Notably, our findings align with those of [PERSON] et al., who reported similar results in healthy young adults after a nine-session balance training intervention using various instability devices [34]. In addition, their study concluded that the degree of instability participants trained with was not a determining factor in the balance improvements achieved.