寬頻網路普及、無線網路提升、雲端技術的發展，使得依賴3G、4G或Wifi的智慧型裝置伴隨著成長， 2010年iPad問世，平板電腦開始引領風潮，逐漸成為人們生活中不可或缺的手持行動裝置，若從人因工程觀點言之，平板電腦需要支撐手握持以方便操作，因此為「手持」行動設備。隨著平板未來將走向大尺吋發展，重量相對於此變成一個棘手的問題，長時間的操作下，對於不同握持姿式平板電腦的支撐手，在肌肉骨骼上仍可能造成不適或傷害。
有鑒於此，本研究透過實驗設計，模擬不同重量下的平板電腦模型，進行操作實驗，研究目的為了解各重量因子與手部握持姿勢對於前臂負荷的影響，實驗階段針對前臂負荷之量測實驗，實驗設計為兩個自變項，分別為重量水準四個：450g、500g、550g、600g；手部握持姿勢兩種：拇指扣壓(Thumb Wrap Posture)、拇指伸展握壓由魚際肌協助(Thumb Extended with Thenar Support)。依變項在客觀方面為前臂肌肉肌電訊號值及手腕角度，主觀方面以柏格自覺費力量表與開放式問卷填寫得知主觀喜好及費力與疲勞感受。
實驗結果顯示，當設計超過550g會顯著影響前臂負荷，建議未來在重量考量設計上不要超過550g，降低傷害發生風險；握持姿式方面，建議以拇指扣壓的姿勢使用平板電腦，對於握持支撐手的負荷較小。對於疲勞而言，無明顯重量因子造成疲勞程度上差異；握持姿勢為造成疲勞顯著影響的因子，其中拇指扣壓較不易造成疲勞產生。希望透過本研究實驗結果，能提供使用者與設計者在未來的使用上或設計方面改善之參考依據。

With the vast development of network, wireless fidelity and cloud technology, the usage of smart devices that depend on 3G, 4G or Wi-Fi technology increase dramatically in recent years. Since the launch of iPad in 2010, tablets have led the trend and have been becoming indispensable handheld mobile devices in our daily life. Tablets, which are regarded as handheld mobile equipment, need to be held on the bracing hand in order to be operated easily. Since the development trend of tablets is set to making the size larger, the weight of tablets becomes a critical issue to consider from human factors engineering perspective. Another issue needs to be thought through is whether different holding postures on the bracing hand can cause damages to the muscle and skeleton under long period of operation.
The purpose of the study is to investigate the effects of forearm limb’s loading under different weights and different holding postures. Four tablet prototypes based on weight are designed in the experiment. Two independent variables, including four different weights of the tablet prototypes and two bracing types of handheld, are considered in the experimental design.Specifically, there are 4 levels for weight :450g,500g, 550g, and 600g; and there are 2 levels for holding postures, namely Thumb Wrap Posture and Thumb Extended with Thenar Support. The psychophysical measurements of the dependent variables are the signal of myoelectricity for forearm limb and the angle of wrist under different weights and holding postures. Borg scales and the open-question questionnaire from users’ perceived exertion and fatigue are used as the subjective assessment.
The experiment result shows that 550g is a upper bound of load, which implies that when the device weight is heavier than 550g it might cause significant impact on forearm limb loading. With this result, a design of tablet no more than 550g is advised to not increase the risk of damages to forearm limb. The experiment result also shows that the posture of Thumb Wrap Posture has less loading than that of Thumb Extended with Thenar Support, which suggests that the former posture is recommended than the latter posture for the bracing hand. However, subjective assessment of fatigue did not show any statistically significant difference among four different weights.
In conclusion, 550g is a upper bound of load and Thumb Wrap Posture shows less fatigue than Thumb Extended with Thenar Support when using tablets. The experiment results provide helpful information for designers to improve the user experiences both psychologically and physically.

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