Neck-shoulder and upper back musculoskeletal symptoms in smartphone users have gained increasing attention. We evaluated trapezius muscle activity and fatigue using an objective method (surface electromyography, sEMG), and discomfort using a subjective method (questionnaire), in smartphone users during the performance of different text-entry tasks. Fifteen participants were recruited to perform six text-entry tasks under different forearm conditions (floating and supported) and body postures (sitting, standing, lying, and walking). We collected upper trapezius (UT) and lower trapezius (LT) sEMG data, and recorded muscle discomfort scores after each task. We found that static postures (especially sitting) during smartphone use predisposed to lower muscle activity with higher fatigue level and discomfort scores than dynamic posture; there was a significant main effect of body posture on average sEMG amplitude (aEMG) and discomfort scores of both muscles (all p < 0.05). Moreover, using a smartphone with the forearm supported can reduce muscle activity, fatigue level, and discomfort scores; there was a significant main effect of the forearm condition on aEMG and discomfort scores of both muscles (all p < 0.05). Our study indicates that smartphone use with the forearm floating for a long time in a static posture should be avoided (especially while sitting).

智能手机用户的颈肩和上背部肌肉骨骼症状得到了越来越多的关注。在执行不同的文本输入任务时，我们使用智能手机用户使用客观方法（表面肌电图，sEMG）评估斜方肌的活动和疲劳，使用主观方法（问卷调查）评估斜方肌的不适。招募了15名参与者，分别在不同的前臂条件（漂浮和支撑）和身体姿势（坐姿，站立，躺卧和行走）下执行六项文本输入任务。我们收集上斜方肌（UT）和下斜方肌（LT）sEMG数据，并记录每项任务后的肌肉不适得分。我们发现，使用智能手机期间的静态姿势（尤其是坐姿）比动态姿势更容易导致肌肉活动降低，疲劳程度和不适感得分更高；姿势对两个肌肉的平均sEMG振幅（aEMG）和不适分数均具有显着的主要影响（所有p <0.05）。此外，使用支持前臂的智能手机可以减少肌肉活动，疲劳程度和不适感。前臂状况对aEMG和两块肌肉的不适感评分都有显着的主要影响（所有p <0.05）。我们的研究表明，应避免使用前臂长时间以静态姿势漂浮的智能手机（尤其是坐着时）。前臂状况对aEMG和两块肌肉的不适感评分都有显着的主要影响（所有p <0.05）。我们的研究表明，应避免使用前臂长时间以静态姿势漂浮的智能手机（尤其是坐着时）。前臂状况对aEMG和两块肌肉的不适感评分都有显着的主要影响（所有p <0.05）。我们的研究表明，应避免使用前臂长时间以静态姿势漂浮的智能手机（尤其是坐着时）。