# Reliability of a Portable Fixed Dynamometer During Different Isometric Hamstring Assessments
## 4 Discussion  
The purpose of this study was to evaluate the within- and between-session reliability of a portable fixed dynamometer for measuring different force-time variables during a range of different hamstring assessments. To gain insight into the full reliability of a measure, it is recommended that systematic changes in mean, absolute and relative consistency are all reported [34]. The main findings were as follows: (1) all variables except peak RFD had acceptable CVs and had good to excellent ICCs for within- and between-session reliability for the standing hamstring assessment; (2) for the supine 90:90 assessment, peak force, mean force and impulse had good to excellent relative within- and between-session reliability, while absolute reliability was found to be acceptable for all but between sessions 2 and 1 for impulse; (3) the 90:20 hamstring assessment had good to excellent relative within- and between-session reliability for all variables except peak RFD, and acceptable absolute reliability for all but between sessions 2 and 1 for impulse; and (4) for most of the variables assessed, values increased depending on the test used, with the lowest values recorded for the standing hamstring test and the greatest values for the 90:20 test. To the authors' knowledge, this was the first study to determine the reliability of a portable fixed dynamometer in measuring a range of different force-time variables during \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Peak Force**} & \multicolumn{2}{c}{**Mean Force**} & \multicolumn{2}{c}{**Impulse**} & \multicolumn{2}{c}{**Peak RFD**} \\  & \multicolumn{2}{c}{**(N)**} & \multicolumn{2}{c}{**(N)**} & \multicolumn{2}{c}{**(N-s)**} & \multicolumn{2}{c}{**(N-s\({}^{-1}\))**} \\ \cline{2-7}
**Variable** & **Mean Difference** & \(p\)**-Value** & **Mean Difference** & \(p\)**-Value** & **Mean Difference** & **Mean Difference** & **Mean Difference** & **\(p\)**-Value** \\  & \(\pm\)**SE** & \(p\)**-Value** & \(\pm\)**SE** & \(p\)**-Value** & **Mean Difference** & \(\pm\)**SE** & \(p\)**-Value** \\ \hline
**Standing vs.** & \(-\)18.62 \(\pm\) 14.36 & 0.652 & \(-\)26.85 \(\pm\) 12.34 & 0.146 & \(-\)129.44 \(\pm\) 46.22 & 0.045 & 28.95 \(\pm\) 164.88 & 1.00 \\
**Standing vs.** & \(-\)163.6 \(\pm\) 23.42 & \(<\)0.001 & \(-\)149.5 \(\pm\) 21.46 & \(<\)0.001 & \(-\)514.46 \(\pm\) 75.82 & \(<\)0.001 & 57.86 \(\pm\) 195.55 & 1.00 \\
**90-90 vs.** & \(-\)144.9 \(\pm\) 21.10 & \(<\)0.001 & \(-\)122.7 \(\pm\) 17.71 & \(<\)0.001 & \(-\)385.02 \(\pm\) 69.88 & \(<\)0.001 & 28.91 \(\pm\) 152.22 & 1.00 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of outputs across the three testing positions. a standing hip extension assessment. In terms of within-session reliability, systematic biases were non-significant, and absolute and relative consistency was good to excellent--CVs were \(\leq\)8.5% and ICCs > 0.83 for peak force, mean force and impulse across the three trials. Similar results were observed for within-session reliability, with peak force, mean force and impulse all having good to excellent reliability--CVs were \(\leq\)9.1% and ICCs were >0.88, and peak RFD was moderate at best (CVs = 28.3-29.2%; ICCs = 0.74-0.80). With regard to previous research, there is limited research that has been performed in this standing position. [PERSON] and [PERSON] [36] compared a standing hip extension isometric contraction measured with an isokinetic dynamometer to a prone position with 90\({}^{\circ}\) knee flexion. The authors did not report on the ICC of the standing position as measured via isokinetic dynamometry. Another research group reported on the within-session reliability of a standing hip isometric endurance protocol measured via EMG (ICC = 0.631-0.98, SEM = 3.39-8.20); however, no force-time metrics were reported. Therefore, this study appears to be the first to quantify the reliability of a novel standing hip extension assessment, which may be suitable for athletes and those in late-stage or return-to-play rehabilitation.