# Arm Posture Changes and Influences on Hand Controller Interaction Evaluation in Virtual Reality
## 5 Results
### Hand Operation Persistence and Perceived Arm Fatigue Assessment
Post-hoc [PERSON]'s tests show that (i) hand-controller interaction over the head was more mentally and physically demanding than that at the shoulder and waist heights; (ii) hand-controller interaction at a higher position was perceived to be more tiring and painful than that at a lower position; moreover, (iii) hand-controller interaction at the shoulder or waist height was perceived to be more relaxed and comfortable with less confusion than that at the head height. Overall, the subjective assessment results on perceived arm fatigue level are highly consistent with the hand duration results. Post-study comments from the participants were collected and analyzed. In general, the comments conformed to the task performance and the questionnaire assessment results. Two participants noted that they felt strained while acquiring targets at an arm-length distance. However, when acquiring targets at a closer distance, hand interaction became more relaxed and durable. This was also reported by the majority of the other participants. Three other participants pointed out that they were more accustomed to using the right hand; five participants added that hand interaction at the waist height and right side of the body was more efficient and comfortable than at other positions; this was also acknowledged by nine other participants. Additionally, two participants commented that the target presented in the experimental program was large enough to be selected precisely at a 30 cm distance; however, when the target was shown at an arm-length distance, target selection became less precise. Their interaction performance objectively reflected this comment, and the other twenty-eight participants also reported this point. In summary, the experiment revealed that arm posture, in particular arm-bending degree, and the hand-operational position are two significant variables influencing hand-controller interaction accuracy in VR. It was found that a stretched arm posture generates more target acquisition errors, at the same time resulting in more scattered end-points, in comparison with the bent or half-bent arm postures. In addition, it was found that a stretched arm posture has a more persistent interaction with fewer hand alternations throughout the interaction task, in comparison with a wholly- or half-bent arm posture. Thus, Hypothesis 1 (H1) is completely supported. It was also found that targets located at the waist height are acquired more accurately than those at the shoulder and overhead heights, while hand operation at a lower position was also found to be more relaxed and to generate a longer duration with fewer hand alternations throughout the task. Based on these findings, Hypothesis 2 (H2) is also supported. Additionally, the hand-use choice effect on hand-controller interaction performance was observed in the experiment. In particular, in the left-hand interaction, acquiring targets on the left side of the body is more accurate than that on the right side; however, in the right-hand interaction, the result is converse. From this perspective, Hypothesis 3 (H3) is also supported. Apart from the hand-use choice effect, the individual handedness characteristic was found to impact interaction persistence, the dominant hand having a longer duration than the non-dominant hand. However, the dominant hand and the non-dominant hand generate no obvious difference on hand-controller interaction accuracy. Hypothesis 4 (H4) is not supported.