Department of Environmental Health, Harvard T.H. Chan School of Public Health, 677 Huntington Ave., Boston, MA, USA.
Department of Physical Therapy, Movement, and Rehabilitation Sciences, Bouvé College of Health Sciences, Northeastern University, 360 Huntington Avenue, Boston, USA.
Appl Ergon. 2018 May;69:40-46. doi: 10.1016/j.apergo.2017.12.015. Epub 2018 Jan 12.
Tablet computers' hardware and software designs may affect upper extremity muscle activity and postures. This study investigated the hypothesis that forearm muscle activity as well as wrist and thumb postures differ during simple gestures across different tablet form factors and touchscreen locations. Sixteen adult (8 female, 8 male) participants completed 320 tablet gestures across four swipe locations, with various tablet sizes (8″ and 10"), tablet orientations (portrait and landscape), swipe orientations (vertical and horizontal), and swipe directions (medial and radial). Three-dimensional motion analysis and surface electromyography measured wrist and thumb postures and forearm muscle activity, respectively. Postures and muscle activity varied significantly across the four swipe locations (p < .0001). Overall, swipe location closest to the palm allowed users to swipe with a more neutral thumb and wrist posture and required less forearm muscle activity. Greater thumb extension and abduction along with greater wrist extension and ulnar deviation was required to reach the target as the target moved farther from the palm. Extensor Carpi Radialis, Extensor Carpi Ulnaris, Flexor Carpi Ulnaris, Extensor Policis Brevis, and Abductor Pollicis Longus muscle activity also increased significantly with greater thumb reach (p < 001). Larger tablet size induced greater Extensor Carpi Radialis, Extensor Carpi Ulnaris, Flexor Carpi Ulnaris, Flexor Carpi Radialis, and Abductor Pollicis Longus muscle activity (p < .0001). The study results demonstrate the importance of swipe locations and suggest that the tablet interface design can be improved to induce more neutral thumb and wrist posture along with lower forearm muscle load.
平板电脑的硬件和软件设计可能会影响上肢肌肉的活动和姿势。本研究假设，在不同的平板电脑外形因素和触摸屏位置下，进行简单手势时，前臂肌肉活动以及手腕和拇指姿势会有所不同。16 名成年参与者（8 名女性，8 名男性）完成了 320 次平板电脑手势，涉及 4 个滑动位置，使用了各种平板电脑尺寸（8 英寸和 10 英寸）、平板电脑方向（纵向和横向）、滑动方向（垂直和水平）以及滑动方向（向心和离心）。三维运动分析和表面肌电图分别测量手腕和拇指姿势以及前臂肌肉活动。姿势和肌肉活动在四个滑动位置之间存在显著差异（p<0.0001）。总体而言，离手掌最近的滑动位置允许用户以更中立的拇指和手腕姿势进行滑动，并且需要较少的前臂肌肉活动。随着目标远离手掌，需要更大的拇指伸展和外展以及更大的手腕伸展和尺侧偏斜才能达到目标。当拇指达到更大的目标距离时，伸腕肌、伸指总肌、尺侧腕屈肌、小指展肌和拇指外展肌的活动也显著增加（p<0.001）。更大的平板电脑尺寸会引起更大的伸腕肌、伸指总肌、尺侧腕屈肌、桡侧腕屈肌和拇指外展肌的活动（p<0.0001）。研究结果表明滑动位置的重要性，并建议改进平板电脑界面设计，以诱导更中立的拇指和手腕姿势以及更低的前臂肌肉负荷。
