## 3 Discussion  
Overall, the results of all phases of the study support the reliability of our instrumented scrum machine. Deadweight calibrations revealed near-perfect reliability between sessions up to 6 months apart and indicated that most load cells were nearly perfectly reliable regardless of warm-up time beyond the initial 15 min. Statistically significant differences were found between load cells, with two load cells seeming to act similarly together and the other cells seeming to act similarly together. However, this is more an artifact of being overpowered in the statistical analysis (a wide range of tested loads during deadweight calibrations, with identical loads used in every calibration procedure, combined with a very small unexplained random error); the load cells are so highly sensitive (\(\sim\)1% of the total \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & **Trial 2-1** & **Trial 3-2** & **Trial 4-3** & **Trial 5-4** &
\begin{tabular}{c} **Average across** \\ **Trials** \\ \end{tabular} \\ \hline \multirow{4}{*}{Raw values} & Change in mean (volts) & 0.01 & 0.10 & 0.04 & 0.18 & NA \\  & (90\% CI) & (\(-\)0.09 to 0.12) & (\(-\)0.01 to 0.21) & (\(-\)0.10 to 0.17) & (0.05 to 0.32) & NA \\  & Typical error (volts) & 0.14 & 0.17 & 0.20 & 0.20 & 0.18 \\  & (90\% CI) & (0.10 to 0.22) & (0.13 to 0.25) & (0.15 to 0.30) & (0.15 to 0.30) & (0.15 to 0.22) \\  & ICC & 0.96 & 0.94 & 0.93 & 0.95 & 0.95 \\  & (90\% CI) & (0.89 to 0.98) & (0.86 to 0.98) & (0.83 to 0.97) & (0.87 to 0.98) & (0.90 to 0.98) \\ \hline \multirow{4}{*}{Log transformed} & Change in mean (\%) & 0.2 & 4.1 & 1.9 & 6.7 & NA \\  & (90\% CI) & (\(-\)5.2 to 6.0) & (\(-\)0.9 to 9.4) & (\(-\)4.0 to 8.1) & (0.6 to 13.2) & NA \\ \cline{1-1}  & Typical error as CV (\%) & 7.5 & 7.6 & 9.3 & 8.8 & 8.4 \\ \cline{1-1}  & (90\% CI) & (5.5 to 12.2) & (5.8 to 11.6) & (7.0 to 14.1) & (6.6 to 13.6) & (7.0 to 10.5) \\ \cline{1-1}  & ICC & 0.95 & 0.95 & 0.93 & 0.95 & 0.95 \\ \cline{1-1}  & (90\% CI) & (0.87 to 0.98) & (0.88 to 0.98) & (0.84 to 0.97) & (0.87 to 0.98) & (0.90 to 0.98) \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Reliability Statistics for Peak Voltage in Human Individual Scrum Trials. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & **Trial 2-1** & **Trial 3-2** & **Trial 4-3** & **Trial 5-4** &
\begin{tabular}{c} **Average** \\ **across** \\ **Trials** \\ \end{tabular} \\ \hline \multirow{4}{*}{Raw values} & Change in mean (volts) & 0.0 & 0.05 & 0.07 & 0.22 & NA \\  & (90\% CI) & (\(-\)0.08 to 0.07) & (\(-\)0.06 to 0.15) & (\(-\)0.04 to 0.19) & (0.12 to 0.32) & NA \\  & Typical error (volts) & 0.10 & 0.16 & 0.18 & 0.14 & 0.15 \\  & (90\% CI) & (0.07 to 0.16) & (0.12 to 0.23) & (0.13 to 0.26) & (0.11 to 0.22) & (0.13 to 0.19) \\  & ICC & 0.97 & 0.92 & 0.91 & 0.96 & 0.94 \\  & (90\% CI) & (0.92 to 0.99) & (0.81 to 0.97) & (0.79 to 0.96) & (0.89 to 0.98) & (0.89 to 0.98) \\ \hline \multirow{4}{*}{Log transformed} & Change in mean (\%) & \(-\)0.3 & 2.8 & 3.6 & 10.6 & NA \\  & (90\% CI) & (\(-\)5.4 to 5.0) & (\(-\)2.3 to 8.2) & (\(-\)2.1 to 9.7) & (6.0 to 15.4) & NA \\ \cline{1-1}  & Typical error as CV & 7.0 & 7.9 & 8.9 & 6.2 & 7.6 \\ \cline{1-1}  & (90\% CI) & (5.2 to 11.4) & (6.0 to 12.0) & (6.7 to 13.5) & (4.7 to 9.6) & (6.4 to 9.5) \\ \cline{1-1}  & ICC & 0.96 & 0.94 & 0.93 & 0.97 & 0.95 \\ \cline{1-1}  & (90\% CI) & (0.88 to 0.99) & (0.86 to 0.98) & (0.82 to 0.97) & (0.92 to 0.99) & (0.91 to 0.98) \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Reliability Statistics for Average Voltage in Human Individual Scrum Trials. variation in volts), and each cell seemed to be reliable within itself, such that we were able to detect a difference (of about 0.18 N, or 0.018 kg) of a practically negligible magnitude. Even if this maximum error was compounded across all eight load cells, compared against just the combined baseline mass of a pack of forward players leaning on the scrum machine in preparation for pushing, the magnitude of the variance between and within load cells is negligible.