Are the Neck Positions and Muscle Activity Observed when Reading a Tablet Similar to That of the Cervical Flexion-Relaxation Onset?

Abstract

OCCUPATIONAL APPLICATIONS Tablet use has become more common in the workplace and people typically use neck flexion interacting with them. In this position, it is common to observe that the cervical extensor muscles go “silent” just before full flexion and the deeper muscles of the spine and other passive tissues support the head. We found that the neck posture adopted when a person is reading a tablet is before the onset when of this phenomenon occurs and that the measured neck extensor muscles are still relatively active. Three participants, though, approached the onset position. This could represent reliance on deeper muscles and passive tissues for head support. These results suggest that practitioners need to educate their patients and employees on risk factors related to mobile computing usage and specifically determine ways to limit neck flexion when using these devices.TECHNICAL ABSTRACT Background: Use of mobile devices at work and home continues to rise. Prolonged neck flexion has been identified as a potential risk factor for neck pain and is a posture commonly used when interacting with these devices. When a person moves their head into flexion, it is common to the flexion-relaxation phenomenon, in which the cervical extensor muscles go “silent” just before full flexion and deeper muscles of the spine and other tissues, such as ligaments, support the head. Purpose: Compare neck position and muscle activity when reading a tablet computer to the flexion-relaxation onset. Methods: Fourteen participants were instrumented with electromyography and reflective markers to measure cervical extensor muscle activity and neck angle, respectively. They performed a cervical flexion-relaxation test, followed by two one-minute trials of reading a tablet on their lap or a table. Results: The flexion-relaxation phenomenon was shown in 12 of 14 participants. There was a significant difference between the cervical flexion relaxation onset (82% range of motion (ROM)) and the neck position for the lap (59% ROM) and table (29% ROM). Cervical extensor muscle activity was significantly higher when reading the tablet (15%–17% MVC) compared to the relaxation phase (8% MVC). Conclusions: Reading a tablet computer in the tested conditions did not exceed the cervical flexion-relaxation onset position. Some participants were within 5% ROM of their onset position, and future work should address the potential that positioning the mobile device closer to one's trunk could lead to larger neck flexion angles with lower muscle activity.