# Development of an Estimation Formula to Evaluate Mission Motion Suitability of Military Jackets
## 4 Discussion  
The estimation formula of this study was developed based on the results of a motion suitability evaluation conducted on a tracked vehicle crew on active duty while performing a mission on an actual tracked vehicle. A total of nine general motions and 12 mission motions were included in the evaluation of the motion suitability of tracked vehicle crews [11]. All mission motions seemed to be different motions, but each of them was related to the other. The results of a correlation analysis conducted to investigate the characteristics \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Military Uniform** & **Motion** &
\begin{tabular}{c} **Developed** \\ **Equation** \\ \end{tabular} & **Real Score** & \(t\)**-Value** \\ \hline Tracked vehicle crew & Ammunition stowing I & 2.98 \(\pm\) 1.21 & 3.20 \(\pm\) 1.32 & 1.190 \\ jacket & Boarding & 2.63 \(\pm\) 0.66 & 2.50 \(\pm\) 1.27 & \(-\)0.424 \\ \hline Military winter jacket & Ammunition stowing I & 3.38 \(\pm\) 0.63 & 3.53 \(\pm\) 0.64 & \(-\)1.121 \\ Boarding & Boarding & 2.85 \(\pm\) 0.52 & 3.20 \(\pm\) 0.94 & \(-\)2.367 \\ \hline \hline \end{tabular} Values are mean \(\pm\) SD.  
\end{table} 
Table 8: Difference between values calculated of estimation formula and actual score (\(n\) = 10). \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Motion** & \multicolumn{3}{c}{**Developed Equation**} \\ \cline{2-4}  & **1 st Test** & **2 nd Test** & **t-Value** \\ \hline Ammunition stowing I & 2.98 \(\pm\) 1.21 & 2.95 \(\pm\) 1.07 & 0.048 \\ Boarding & 2.63 \(\pm\) 0.66 & 2.68 \(\pm\) 0.78 & \(-\)0.136 \\ \hline \hline \end{tabular} Values are mean \(\pm\) SD.  
\end{table} 
Table 9: Differences in values calculated of the estimation formula according to the test (\(n\) = 10). and correlation of mission motion showed that boarding was highly correlated with other motions performed in a narrow space, such as seating, escaping, getting off, driving I, driving II, and maintenance (\(p<0.05\), \(p<0.01\), \(p<0.001\)). Ammunition stowing I was highly related to seating and maintenance but showed the highest correlation with ammunition stowing II (r = 0.829). Ammunition loading motion carried out in pairs and motions, such as raising and receiving ammunitions, was performed simultaneously. Thus, these motions are correlated, including bending motions. These results suggest that actions can be grouped according to the similarity of the mission motion, and alternative evaluations may be conducted using representative motions that are highly correlated with other motions. As a result of the factor analysis, two mission motion factors were extracted from a total of 12 mission motions used to evaluate the motion suitability of the tracked vehicle crew. These motions are related to ammunition loading using the shoulder and trunk joints (Factor 1), as well as boarding and entering the vehicle using the trunk joint (Factor 2). These two factors had high explanatory power, accounting for 95.01% of the mission motions. This means that the overall mission motion suitability evaluation for a tracked vehicle crew can be explained using these two factors as representative mission motions. The estimation formula for the two factors developed in this study was based on the correlation between the mission motion and general motion. Ammunition stowing I and ammunition stowing II were highly positively correlated with the stand erect, shoulder flexion 180\({}^{\circ}\), shoulder extension, horizontal shoulder abduction 90\({}^{\circ}\), and trunk flexion (\(p<0.001\)). Boarding and entry were correlated with trunk flexion (\(p<0.01\)). This means that it is possible to evaluate the mission motion suitability of a tracked vehicle crew jacket through the performance of five general motions. Furthermore, ammunition stowing motion must be performed by at least three crew members in the mission protocol. However, when evaluating general motion, it can be performed individually and may be evaluated without time and space restrictions.