# Arm Posture Changes and Influences on Hand Controller Interaction Evaluation in Virtual Reality
## 5 Results
### Hand Operation Persistence and Perceived Arm Fatigue Assessment  
According to a measurement by [PERSON] et al. [13], a more tiring arm posture leads to a shorter duration and more frequent alternations between two arms, suggesting that the hand-operational task is less coherent. In this regard, hand-operational persistence can be used as an independent metric in hand-controller interaction evaluations. The hand alternation moments were recorded in the task log files and the interaction duration times of each hand in different conditions of _Hand-use choice \(\times\) Arm's Bending Degree \(\times\) Hand-Operational Height \(\times\) Horizontal Angle_ were calculated, as presented in Table 5. A two-tailed T-test showed that the right hand interaction generates a significantly longer duration time than the left hand interaction (mean duration time of the left hand: 162.3 s; mean duration time of the right hand: 179.2 s; \(t(1349)=-2.59\), \(p<0.05\)). Given all participants were right-handed users, this indicates that the dominant hand has a higher persistence than the non-dominant hand in completing the interaction tasks. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Hand-Use Choice**} & \multirow{2}{*}{**Arm-Bending Degree**} & \multicolumn{6}{c}{**Mean Duration Time (in Seconds), Std. Dev.**} \\ \cline{3-10}  & & \multicolumn{3}{c}{**Hand-Operational Height**} & \multicolumn{3}{c}{**Horizontal Angle**} \\ \cline{3-10}  & & **Overhead** & **Shoulder** & **Waist** & \(\mathbf{-90^{\circ}}\) & \(\mathbf{-45^{\circ}}\) & \(\mathbf{0^{\circ}}\) & \(\mathbf{45^{\circ}}\) & \(\mathbf{90^{\circ}}\) \\ \hline \multirow{6}{*}{Left hand} & \multirow{2}{*}{Wholly-bent} & 175.4, & 191.7, & 233.6, & 146.4, & 226.1, & 196.6, & 160.1, & 141.3, \\  & & 27.92 & 30.61 & 37.94 & 23.35 & 36.43 & 37.72 & 25.64 & 22.48 \\ \cline{2-10}  & \multirow{2}{*}{Half-bent} & 150.2, & 163.0, & 216.2, & 155.2, & 189.9, & 174.6, & 132.2, & 127.7, \\  & & 23.77 & 28.87 & 33.27 & 26.62 & 23.48 & 30.02 & 22.23 & 23.82 \\ \cline{2-10}  & \multirow{2}{*}{Stretched} & 127.3, & 135.3, & 188.4, & 130.3, & 170.7, & 142.5, & 119.6, & 101.2, \\  & & 20.48 & 25.49 & 27.63 & 19.49 & 26.77 & 25.31 & 17.72 & 20.22 \\ \hline \multirow{6}{*}{Right hand} & \multirow{2}{*}{Wholly-bent} & 202.2, & 215.0, & 258.2, & 157.4, & 177.4, & 213.9, & 238.4, & 164.8, \\  & & 32.23 & 37.48 & 37.78 & 30.46 & 30.82 & 41.22 & 43.37 & 29.21 \\ \cline{1-1} \cline{2-10}  & \multirow{2}{*}{Half-bent} & 167.3, & 188.5, & 234.1, & 140.8, & 148.7, & 186.4, & 202.5, & 173.2, \\  & & 30.45 & 30.69 & 30.34 & 24.66 & 23.39 & 33.14 & 30.43 & 30.33 \\ \cline{1-1} \cline{2-10}  & \multirow{2}{*}{Stretched} & 139.8, & 152.4, & 208.6, & 115.5, & 130.8, & 158.5, & 181.6, & 143.9, \\  & & 25.77 & 27.41 & 30.12 & 20.02 & 19.24 & 28.91 & 28.35 & 22.75 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Hand durations (in seconds) in different conditions of hand-use choice, hand-operational position and arm-bending degree. Figure 9: End-point scatter in the depth-direction. A repeated-measures ANOVA was further conducted to analyze the hand duration result. It revealed a significant effect of the _Arm-bending degree_ (\(F(2,\,118)=212.4,\,p<0.05\)), a significant effect of _Hand-Operational Height_ (\(F(2,\,118)=130.7,\,p<0.05\)), and a significant effect of _Horizontal Angle_ (\(F(4,\,236)=99.8,\,p<0.05\)) on the hand duration result. Post-hoc Tukey HSD pairwise comparisons between different arm-bending degrees showed that a stretched arm generates the shortest duration time, while a wholly-bent arm generates the longest duration time (_M(stretched)_ = 146.7 s, _M(half-bent)_ = 171.9 s, _M(wholly-bent)_ = 193.7 s; all \(p<0.05\)), as plotted in Figure 10a. Pairwise comparisons between hand-operational heights showed that the hand interaction at a higher position generates a shorter duration time (_M(overhead)_ = 160.37 s, _M(shoulder)_ = 174.32 s, _M(waist)_ = 223.18 s; all \(p<0.05\)).