Publication in: Spring 2023 Issue

Evaluating the Relationship Between Posture and Muscle strain in the Neck and Wrist: An EMG Analysis
Margarita Rudisill
Faculty Mentor(s):
Christopher Nicolay
Abstract / Summary:
The average American uses their phone around 5 hours a day, and college students average 8 hours a day, with texting being the most frequent task. Along with the rapid increase in the number of smartphone users, health issues associated with overuse of the device have grown too. Studies have linked prolonged use of phones to musculoskeletal disorders because of the low amplitude, repetitive force movements that are done while texting and scrolling. This study uses EMG to investigate the impact of different postures on patterns of muscle use while using cell phones. The study recruited a sample of college students aged 19-63. Measurements were collected of the participants' hand and arm dimensions, maximum grip strength, and thumb pinch strength, and frequency of phone usage. Surface EMG was then used to record the electrical activity of 3 muscle groups: (1), muscles that function as flexors of the thumb and digits (anterior forearm),, (2), extensors of the thumb and wrist (posterior-lateral forearm),, and (3), neck and shoulder muscles (trapezius),. Participants typed a standardized script on their cellphones, while sitting in each of eight different postures that reflect common positions while using a phone. activity of the neck muscles was lowest when the phone was rested in the lap while sitting in a reclined posture in a chair, and highest when the phone is rested on a table and the user is hunched forward. The posterior and anterior forearms were least strained (lowest EMG readings), when the phone was held in the air, compared to resting on the table or in the lap, but seated posture had no significant effect. These results have implications for understanding the optimal ergonomic seated position during electronic device use, which may be used to help minimize the risk of pathology from muscle overuse.
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