## 4 Discussion  
This study aimed to assess the reliability of the scores calculated by a virtual reality device during two games and their association with executive performance in young elite rugby players. The main results of this study were: the relative and absolute reliability of the scores computed during the _Tracker Master_ and _Beat Master_--_Never Stop_ games were poor to moderate, while they were considered good to very good during the _Turbo_ version. Interestingly, the scores were strongly to very strongly associated with executive performance. The association between the calculated scores and inhibition or cognitive flexibility performance of the modified Stroop task (assessed by the error rate or the reaction time) was expected, since these cognitive functions are widely used both during VR games and Stroop tasks. Therefore, participants with the highest scores during the games also had lower error rates and faster reaction times. This indicates that the use of these games during the players' preparation is likely to improve these executive functions; however, this also indicates that the calculated scores can be used to monitor internal training load and prevent overreaching. Among the different reliability indices, the MD is essential to interpret the variation of a measure over time, which is the purpose of training load monitoring. In fact, MD represents the limit under which the observed difference is within what we expect to see \begin{table}
\begin{tabular}{c c c c c} \hline \hline  & \multicolumn{2}{c}{**Flexibility**} & \multicolumn{2}{c}{**Inhibition**} \\ \hline _Beat Master_—_Never Stop_ & **Mean RT** & **\% Success** & **Mean RT** & **\% Success** \\ \hline Achievement & \(-\)0.46 & \(-\)0.01 & \(-\)0.52 * & 0.56 * \\ \hline F1 score & \(-\)0.47 & 0.00 & \(-\)0.65 ** & 0.72 ** \\ \hline Accuracy & \(-\)0.48 & 0.01 & \(-\)0.50 * & 0.60 * \\ \hline Sensibility & \(-\)0.38 & \(-\)0.01 & \(-\)0.82 ** & 0.84 ** \\ \hline Efficiency & \(-\)0.48 & 0.00 & \(-\)0.65 ** & 0.72 ** \\ \hline _Beat Master_—_Turbo_ & & & & \\ \hline Achievement & \(-\)0.19 & \(-\)0.30 & \(-\)0.15 & 0.09 \\ \hline F1 score & \(-\)0.31 & \(-\)0.27 & \(-\)0.08 & 0.03 \\ \hline Accuracy & \(-\)0.35 & \(-\)0.27 & 0.05 & \(-\)0.06 \\ \hline Sensibility & \(-\)0.11 & \(-\)0.23 & \(-\)0.40 & 0.26 \\ \hline Efficiency & \(-\)0.32 & \(-\)0.27 & \(-\)0.07 & 0.03 \\ \hline _Tracker Master_ & & & & \\ \hline Achievement & \(-\)0.21 & \(-\)0.05 & 0.29 & \(-\)0.26 \\ \hline F1 score & \(-\)0.57 * & 0.16 & \(-\)0.03 & \(-\)0.05 \\ \hline Accuracy & 0.04 & \(-\)0.01 & 0.19 & \(-\)0.29 \\ \hline Sensibility & \(-\)0.64 ** & 0.18 & \(-\)0.11 & 0.06 \\ \hline Efficiency & \(-\)0.55 * & 0.16 & 0.05 & \(-\)0.14 \\ \hline \hline \end{tabular} Mean RT: mean reaction time; * significative association with \(p<0.05\); ** significative association with \(p<0.01\).  
\end{table} 
Table 2: Association between the scores provided by the virtual reality device during the games and executive performance during the computerized modified Stroop task. in repeated testing due to the measurement's noise. The smaller this limit, the better the capacity to interpret the variations of a measure. In our study, MD ranges from 5.5 to 44.3%. This heterogeneity must be accounted for when choosing the indices used in the follow-up. It also underlines the need to standardize the conditions of use as much as possible, whether in terms of the environment or scheduling. When considering their reliability characteristics and their level of association with executive performance, sensibility scores measured during the _Beat Master_--_Never Stop_ game (MD = 8.3% and r = \(-\)0.82) or during the _Tracker Master_ game (MD = 11.1% and r = \(-\)0.64) represent the best compromise. The absence of a learning effect during the test-retest (\(p>0.05\) and g \(<0.58\)) suggests they can be used without familiarization.