# Predictive Validity of the Single Leg Hamstring Bridge Test in Military Settings
## 4 Discussion  
The main finding of our study is that the SLHBT shows acceptable reproducibility in a military setting and has moderate predictive validity to discriminate between soldiers with poor and good overall physical fitness performance using a cut-off value of 20 repetitions. In a previous study, the SLHBT was performed on rugby players and showed good to excellent reproducibility with intra-rater intraclass correlation coefficient (ICC) values in the range of 0.77-0.89 [19]. This is in line with our results, where the ICC range was 0.77-0.96, indicating slightly better results. The usefulness of the SLHBT was additionally confirmed by low SEM % (the limit for the smallest change that indicates a real improvement for a group of participants following given intervention; e.g., exercise training) and SRD % values (the smallest change that indicates a real improvement for a single participant) [27], and no signs of systematic error on Bland-Altman plots. Our research group was the first to report performance (including percentile ranks) on this test in the military population [8], where male soldiers have reached 30 and 27 repetitions for the right and left leg, respectively, which was comparable with healthy semi-elite Australian football players who reached 26 repetitions [19]. The original test authors have suggested three cut-off values of 20, 21-30, and \(>\)30 repetitions for poor, average, and good hamstring strength, respectively. They have also reported that athletes with poor hamstring strength (\(<\)20 reps) have an increased risk for hamstring strain injury, indicating the possible importance of this test to screen and identify athletes at risk and to evaluate their physical readiness for return to sport. Our ROC analysis has shown that a cut-off point of 20 repetitions can be used in a military setting if we want to discriminate between soldiers with poor and good overall physical fitness performance (as measured by APFT and FPFT). The AUC in our study was 0.756 (\(p<0.001\)) and knowing that a \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Fitness Test** & \begin{tabular}{c} **SLHBT** \\ **Performance** \\ \end{tabular} & **N** & **Mean** & **SD** & **F** & \begin{tabular}{c} **Mean** \\ **Difference** \\ \end{tabular} & **Sig.** & \begin{tabular}{c} **Partial Eta** \\ **Squared** \\ \end{tabular} \\ \hline \multirow{3}{*}{\begin{tabular}{c} Plank test \\ (seconds) \\ \end{tabular} } & Weak & 45 & 97 & 42 \\ \cline{2-8}  & Good & 136 & 129 & 49 \\ \hline \multirow{3}{*}{\begin{tabular}{c} Pull-ups (\#) \\ \end{tabular} } & Weak & 45 & 3 & 3 \\ \cline{2-8}  & Good & 136 & 6 & 4 \\ \hline \multirow{3}{*}{\begin{tabular}{c} CMJ (cm) \\ \end{tabular} } & Weak & 45 & 27.0 & 4.3 \\ \cline{2-8}  & Good & 136 & 28.2 & 4.1 \\ \hline \multirow{3}{*}{\begin{tabular}{c} Loaded CMJ (cm) \\ \end{tabular} } & Weak & 45 & 24.5 & 4.3 \\ \cline{2-8}  & Good & 136 & 25.2 & 4.4 \\ \hline \multirow{3}{*}{\begin{tabular}{c} Push-ups (\#) \\ \end{tabular} } & Weak & 45 & 66 & 12 \\ \cline{2-8}  & Good & 136 & 70 & 10 \\ \hline \multirow{3}{*}{\
\begin{tabular}{c} Trunk raises (\#) \\ \end{tabular} } & Weak & 45 & 67 & 13 \\ \cline{2-8}  & Good & 136 & 75 & 11 \\ \hline \multirow{3}{*}{
\begin{tabular}{c} Two-mile run (min) \\ \end{tabular} } & Weak & 45 & 15:31 & 1:19 \\ \cline{2-8}  & Good & 136 & 14:31 & 1:12 \\ \hline \hline \end{tabular}  
* SLBHT performance: good \(\geq\)21 repetition; weak \(\leq\)20 repetitions. (\#)—number of repetitions. CMJ—countermovement jump.  
\end{table} 
Table 2: Differences in the physical performance of soldiers with different hamstring strengths. diagnostic test with AUC value equal to 1 is perfectly accurate, whereas a value equal to 0.5 has no discrimination power, we may conclude that this value corresponds to a large effect size [28].