Abstract：
This study recruited 30 young participants (15 men and 15 women) to examine the smartphone usage patterns in three postures (standing, supported sitting, and unsupported sitting) and at five head angle (HA) positions (0°-40°). Cervical erector spinae (CES) and upper trapezius (UTZ) muscle activity, neck flexion (NF), gaze angle (GA), viewing distance (VD), and discomfort scores were collected. Results showed that HA and posture almost affected all responses, while CES muscle activity, NF, and VD differed between sexes. Strain in the neck and shoulder region increased with HA increase. Particularly, when the HA exceeded 20°, the discomfort scores considerably increased. Unsupported sitting should be avoided during smartphone use because of relatively poor responses in all variables. However, both standing and supported sitting have their respective benefits. Sex-related differences were typically observed in the standing position, with women tending to have lower NF but higher CES muscle activity compared with men.Practitioner summary: Although smartphones have become daily necessities, the overall quantitative neck and shoulder strain of using smartphones in different postures is rarely evaluated. We suggest that maintaining the HA within 20° is recommended because of relatively low load on the neck and shoulders. An unsupported sitting should be avoided during smartphone use.
摘要：
这项研究招募了30名年轻参与者（15名男性和15名女性），以三种姿势检查智能手机的使用模式（站立，支持坐,和无支撑的坐姿）和五个头角（HA）位置（0°-40°）。颈竖脊肌（CES）和上斜方肌（UTZ）肌肉活动，颈屈曲(NF),注视角度(GA),观看距离(VD),并收集不适评分。结果表明，HA和姿势几乎影响所有反应，而CES肌肉活动，NF,VD在性别之间有所不同。颈部和肩部的应变随HA的增加而增加。特别是,当HA超过20°时，不适评分大大增加。在使用智能手机期间，应避免不受支持的坐姿，因为所有变量的响应都相对较差。然而,站立和支撑坐都有各自的好处。通常在站立姿势中观察到性别相关的差异，与男性相比，女性倾向于有较低的NF，但较高的CES肌肉活动。从业者总结：虽然智能手机已经成为日常必需品，很少评估在不同姿势下使用智能手机的整体定量颈部和肩部疲劳。我们建议将HA保持在20°以内，因为颈部和肩部的负荷相对较低。在使用智能手机时应避免不受支持的坐姿。
