# Arm Posture Changes and Influences on Hand Controller Interaction Evaluation in Virtual Reality
## 5 Results
### Hand Operation Persistence and Perceived Arm Fatigue Assessment
More specifically, hand-controller interaction with the arm raised above the head is more tiring than that at the shoulder height, which is more tiring than that at the waist height, as plotted in Figure 10b. There was also a significant interaction effect of _Hand-use choice_\(\times\)_Horizontal Angle_ on the hand duration result (\(F(4,\,236)=182.1,\,p<0.05\)), as shown in Figure 10c. Further statistical analyses were conducted for each hand. In the left hand interaction, hand duration on the left side of the body (at horizontal angles of \(-90^{\circ}\) and \(-45^{\circ}\)) was significantly longer than that on the right side (at horizontal angles of \(45^{\circ}\) and \(90^{\circ}\)) (\(M(-90^{\circ},\,-45^{\circ})=169.77,\,M(45^{\circ},\,90^{\circ})=130.35;\,t( 539)=7.37,\,p<0.05\)). However, in the right hand interaction, the result was converse: hand duration on the left side of the body was significantly shorter than that on the right side (\(M(-90^{\circ},\,-45^{\circ})=145.10,\,M(45^{\circ},\,90^{\circ})=184.07;\,t( 539)=-10.22,\,p<0.05\)). In this experiment, a subjective assessment on perceived arm fatigue was conducted to verify the hand duration result. As interpreted in the section of the experiment proce  
Figure 10: Hand duration comparisons in different conditions: (**a**) result at different bending degrees of the arm; (**b**) result at different hand-operational height; and (**c**) result at different horizontal angles. dure, the subjective assessment was measured through a post-block questionnaire, which focused on six metrics: _Mental Demand, Physical Demand, Temporal Demand, Effort, Performance, and Frustration Level_. Each metric consisted of a detailed statement, as presented in Appendix A--Table A1. Participants rated the statements on a 5-point Likert scale from'strongly disagree' to'strongly agree'. Figure 11 shows the perceived arm fatigue result in boxplots, in different conditions of hand-use choice, arm-bending degree and hand-operational height. A Mann-Whitney test showed a significant effect of Hand Choice on _Physical Demand_ (_U_ = 78.92, \(p\) < 0.05), on _Temporal Demand_ (_U_ = 145.06, \(p\) < 0.05), on _Performance_ (_U_ = 60.43, \(p\) < 0.05) and on _Frustration Level_ (_U_ = 96.70, \(p\) < 0.05). More specifically, (i) the left-hand interaction was perceived to be more physically demanding than the right-hand interaction; (ii) the former was perceived to be more suffering and burdensome than the latter in completing the task; (iii) the left-hand interaction was also perceived to be more successful and efficient with less frustration than the right-hand interaction. Next, a Kruskal-Wallis analysis on perceived arm-fatigue level was conducted. It shows a significant effect of the _Arm-bending degree_ on _Mental Demand_ (\(\chi^{2}_{2}\) = 15.81, \(p\) < 0.05), _Physical Demand_ (\(\chi^{2}_{2}\) = 27.28, \(p\) < 0.05), _Temporal Demand_ (\(\chi^{2}_{2}\) = 52.02, \(p\) < 0.05), _Performance_ (\(\chi^{2}_{2}\) = 11.14, \(p\) < 0.05) and _Frustration Level_ (\(\chi^{2}_{2}\) = 20.61, \(p\) < 0.05). Post-hoc [PERSON]'s comparisons show that (i) the bent arm posture was perceived to be more mentally and physically demanding than the stretched arm posture; (ii) the stretched arm posture was more tiring and suffering than the wholly- and half- bent arm postures; (iii) the bent posture was  
Figure 11: Perceived arm fatigue level in different conditions of hand choice, the arm’s bending degree and the hand-operational height. perceived to be more accustomed by and efficient in completing the interaction tasks with less frustration than the stretched arm posture. It also shows that the _Hand-Operational Height_ has a significant effect on perceived arm-fatigue level, in terms of _Mental Demand_ (\(\chi^{2}_{2}\) = 21.09, \(p\) < 0.05), _Physical Demand_ (\(\chi^{2}_{2}\) = 35.11, \(p\) < 0.05), _Temporal Demand_ (\(\chi^{2}_{2}\) = 19.74, \(p\) < 0.05), _Effort_ (\(\chi^{2}_{2}\) = 40.02, \(p\) < 0.05) and _Frustration Level_ (\(\chi^{2}_{2}\) = 45.30, \(p\) < 0.05).