本研究鑒於現今多點觸控式螢幕使用之普及性與使用姿勢安全的重要性,遂以三實驗與觀察研究進行探討。實驗一為測量觀看14個不同螢幕角度設定之視覺績效。實驗二為觀看螢幕時之頸部維持在一設定角度下之肌電訊號(EMG)。實驗三則探討使用觸控螢幕時之螢幕角度與上肢肌肉疲勞程度及姿勢的關係。研究結果顯示:(1)實驗一:觸控螢幕角度在於45°、60°、75°、90°及105°時,可提供良好的可讀取性。(2)實驗二:肌電訊號顯示,當頸部直立呈現90°時之肌肉疲勞度最少,次為75°,再者為60°,最差為45°且最為疲勞之角度。(3)實驗三:(a)上肢操作時之三角肌與斜方肌部位最為疲勞。(b)使用者以手指支撐在螢幕邊緣,以使點選更加的精準。(c)當點選較小的面積之圖像符號時,使用者身體習慣往螢幕方向前傾,使眼睛更靠近螢幕以便更加準確點選目標物。(d)當使用者手指進行縮放、旋轉及拖曳螢幕上的物件時,主要以食指與拇指合作、或是中指與拇指合作操作。(e)使用者上肢與身體呈現不自然姿勢,且操作後抱怨其肌肉骨骼之不適現象。
Multi-touch screens are popular and upper-limb posture is an important safety issue. This study therefore presents an ergonomic investigation of the visual performance of multi-touch screens and the upper-limb postures adopted while using them. The visual performance associated with viewing the text on the screen at 14 angles is experimentally examined. The muscle fatigue in the neck is explored using EMG measurements at different neck bending downwards. In the third experiment, the relationship between muscle fatigue and upper-limb posture while the touch-screen is being used, is examined. Statistical analysis reveals that: (1)the best visual performance is achieved when the screen angle is set between 30 and 120 degrees; (2)according to EMG measurements, the lowest muscle fatigue is when the neck is bent downward at 90°, following by a bending angle of 75°, followed by a bending angle of 60°; muscle fatigue is high when the neck angle is downward at 45°; (3)(a)the Trapeziu and Deltoid exhibit the greatest muscular effort; (b)fingers can be used as a local support on the edge of the screen for pointing-and-clicking; (c)users’ bodies tend to lean forward toward screen during pointing-and-clicking; (d)users use two hand gestures(one with the index and middle fingers, and one with the thumb and middle finger)to zoom in on, rotate and drag objects on the screen, and (e)unnatural postures are adopted when the multi-screen is used, causing users to complain about musculoskeletal disorders.