Abstract
The goal of this study was to evaluate how chair support (armrest and back support) affect the head/neck kinematics and muscle activity as compared to no chair support among four different phone positions (eye, chest, lap, and self-selected level). In a repeated-measures laboratory experiment with 20 subjects (10 males and 10 females), we measured head/neck flexion angle, gravitational moment and muscle activity in upper trapezius (TRAP) and splenius capitis (SPL). The results showed that chair support significantly reduced the head/neck flexion (p’s < 0.001), gravitational moment (p < 0.001), and muscle activity in TRAP and SPL (p’s < 0.001). With chair support, holding a phone at self-selected levels resulted in the largest reduction in head/neck flexion angle and gravitational moment while the eye-level location showed the lowest neck/shoulder muscle activity. The study findings indicate that the mobile phone use with adequate chair support may significantly reduce the physical stress in the neck and shoulder regions as compared to no chair support.
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