Linking head and neck posture with muscular activity and perceived discomfort during prolonged smartphone texting

Prolonged use of the smartphone for texting was studied on a sample of 17 healthy young adult participants (11 females), who were asked to type interactively on a handheld device while standing and sitting. Upper body kinematics ad upper trapezius surface EMG were recorded to capture parameters of joint kinematics and muscular activity, which were then compared with self-reported indicators of discomfort through the Borg's CR 10 scale questionnaire. The results indicated that, while showing a similar postural strategy in both conditions that is assumed to be controlled by the visual system to maintain a constant viewing distance from the device, the participants adopted a “stiffer” posture of the head and neck during standing than when sitting, with a direct correlation between upper trapezius muscle activity, neck angle and perceived discomfort. The evidence obtained in this study highlights the importance of monitoring muscle activity and head and neck kinematics, to assess the biomechanical risk factors of neuromuscular disorders associated with smartphone overuse.